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LIBRARY
Michigan State
University

This is to certify that the
dissertation entitled

PASSERINE PRODUCTIVITY AND PCB EXPOSURE AT
THE KALAMAZOO RIVER SUPERFUND SITE, MICHIGAN

presented by

Arianne Marie Neigh

has been accepted towards fulfillment
of the requirements for the

Ph.D. degree in Zoology and Center for
Integated Toxicology

 

 

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PLACE IN RETURN BOX to remove this checkout from your record.
To AVOID FINES return on or before date due.
MAY BE RECALLED with earlier due date if requested.

 

DATE DUE

DATE DUE

DATE DUE

 

APR 13 2007

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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PASSERINE PRODUCTIVITY AND PCB EXPOSURE AT THE KALAMAZOO
RIVER SUPERFUND SITE, MICHIGAN

By

Arianne Marie Neigh

A DISSERTATION

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY
Department of Zoology and Center for Integrated Toxicology

2004

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ABSTRACT
PASSERINE PRODUCTIVITY AND PCB EXPOSURE AT THE KALAMAZOO
RIVER SUPERFUND SITE, MICHIGAN
By

Arianne Marie Neigh

The Kalamazoo River basin contains soils and sediments contaminated with
polychlorinated biphenyls (PCBs). In an effort to assess risk to wildlife species, studies
in support of an ecological risk assessment were conducted using four passerine species.
Risk to the tree swallow (T achycineta bicolor), eastern bluebird (Sialia sialis), house
wren (T roglodytes aedon), and American robin (T urdus migratorius) were quantified
using three lines of evidence. These included, the bottom-up approach (dietary exposure
assessment), top-down approach (tissue-based exposure assessment), and measurements
of population health. Goals of the studies were to: quantify risk in the passerine
receptors; evaluate various approaches to the risk assessment process; advance the
scientific understanding of passerine exposures and effects from this class of compounds
utilizing field-based methodologies; provide site-specific data to aid risk managers in
making effective remedial decisions; and provide baseline data to evaluate remedial

decisions.

Overall, the lines of evidence with the highest certainty arrived at similar conclusions
based on studies consisting of 144 nest boxes spread equally between a downstream

location contaminated with PCBs and an upstream reference site with background levels

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of contamination. The top-down approach, which investigated tissue concentrations of
PCBs contained in eggs, nestlings, and adults of each bird species, found concentrations
in tissues at the contaminated location to be significantly greater than concentrations at
the reference site. Concentrations of PCBs in tissues were below the threshold at which
effects would be expected, and so, little risk was associated with concentrations in
tissues. The bottom-up approach quantified concentrations of PCBs in the diet of the
avian species. Concentrations of PCBs in the diet at contaminated locations were 6 to 35-
fold greater than at background locations. Risk associated with dietary exposure was
below the threshold for effects when contaminants were quantified as total PCBs.
Dietary PCB exposures converted to a measure of dioxin-like toxicity exceeded one of
two dietary threshold values. However, the confidence associated with these thresholds
was low and ultimately suggested the presence of risk due to dietary exposure is low.
Dioxin-like toxicity approaches based on dietary exposure were highly dependent on the
selection of threshold values. In this instance, little data was available to derive, species—
specific thresholds, which introduced uncertainty to the calculation of risk. The final line
of evidence suggested little harm to population health due to PCB exposure. Based on
these studies, it is unlikely that the four passerine species examined are experiencing
adverse effects from PCBs present in the local environment. It should be noted that at
many sites similar to this one, a single line of evidence, most often dietary exposure, is
utilized to derive risk conclusions. This study highlights the necessity of utilizing a site-
specific, weighted, multiple lines of evidence approach to arrive at the best estimate of

risk.

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ACKNOWLEDEMENTS

I would like to extend a special thanks to the students and technicians at the Michigan
State University Aquatic Toxicology Laboratory. Monica MacCarroll, Carrie Ruppert,
Breton Joldersma, Ryan Holem, and Cyrus Park were all invaluable in every aspect of
this research including sample collection, processing, and data analysis. I would also like
to thank Patrick Bradley and Michael Kramer for their speed and precision in the
laboratory, and all of the scientists at Entrix, Inc. including: Matt Zwiemik, Alan
Blankenship, Denise Kay, Paul Jones, John Newsted, Katie Coady, and Karen Smyth.
Mark Markham, I will never forget your love and support. Also, many thanks to my
committee for review of this document including John Giesy, Caterhine Lindell, Jan
Stevenson, and Steve Bursian. This study was conducted in cooperation with the
Kalamazoo Nature Center whose staff was instrumental in field collection. The

Kalamazoo River Study Group generously provided funding for this study.

 

 

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TABLE OF CONTENTS

LIST OF TABLES ..................................................................................................... vii
LIST OF FIGURES ................................................................................................... ix
KEY TO ABBREVIATIONS .................................................................................... xi
CHAPTER 1

PRODUCTIVITY OF TREE SWALLOW (TACHYCINETA
BICOLOR) EXPOSED TO PCBS AT THE KALAMAZOO
RIVER SUPERFUND SITE ...................................................................................... 1

CHAPTER 2

TREE SWALLOW (TA CHYCINETA BIC OLOR) EXPOSURE TO
POLYCHLORINATED BIPHENYLS AT THE KALAMAZOO

RIVER SUPERFUND SITE ...................................................................................... 40

CHAPTER 3
REPRODUCTIVE SUCCESS OF PASSERINES EXPOSED TO
PCBS THROUGH THE TERRESTRIAL FOOD WEB OF THE

KALAMAZOO RIVER ............................................................................................. 82
CHAPTER 4

ACCUMULATION OF POLYCHLORINATED BIPHENYLS

(PCBS) FROM FLOODPLAIN SOILS BY PASSERINE BIRDS ........................... 117
CHAPTER 5

MULTIPLE LINES OF EVIDENCE ASSESSMENT OF PCBS IN
THE DIETS OF PASSERINE BIRDS AT THE KALAMAZOO
RIVER SUPERFUND SITE, MICHIGAN ................................................................ 157

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LIST OF TABLES

Table 1.]. Reproductive productivity measurements (mean (SD)) for tree swallows at the
reference site (FC) and at a PCB contaminated target site (TB) at the Kalamazoo River
Area of Concern (KRAOC) ....................................................................................... 15

Table 1.2. Nest fate and percent of total nests initiated at the Fort Custer (FC) reference
site and the Trowbridge (TB) target site for nests in which eggs were laid .............. 17

Table 1.3. Mean (SD)8 reproductive endpoints for tree swallow eggs and nestlings (12-d-
old) reared at the Fort Custer State Recreation Area and at the Trowbridge Impoundment
along the Kalamazoo River Area of Concern ............................................................ 18

Table 1.4. Tree swallow nestling weight (g) expressed as the mean nestling weight in
each nest at the upstream Fort Custer reference area and the former Trowbridge
Impoundment from 2000 to 2002 .............................................................................. 20

Table 1.5. Power (l-B) and sample size (N) needed to detect a 20% reduction in
reproductive success at the Trowbridge Impoundment compared to the Fort Custer State
Recreation Area ......................................................................................................... 27

Table 2.1. Literature-derived tree swallow toxicity reference values (TRVs) used to
calculate hazard quotients based on the no observed adverse effect level (NOAEL) and
the lowest observed adverse effect level (LOAEL). Reference number is located next to
each value ................................. 54

Table 2.2. Mean (:t 1 SD) total polychlorinated biphenyl (PCB) concentrations (wet
weight) and lipid content of tree swallow tissue samples from the Fort Custer State

Recreation Area (reference location) and the former Trowbridge Impoundment within the
Kalamazoo River Area of Concern (KRAOC) .......................................................... 56

Table 2.3. 2, 3, 7, 8- tetrachlorodibenzo-p-dioxin equivalents (TEQs) and relative potency
in tree swallow tissues sampled from the Fort Custer Reference location and the former
Trowbridge Impoundment within the Kalamazoo River Area of Concern

(KRAOC) ................................................................................................................... 58

Table 2.4. Biomagnification factors for tree swallows on the Kalamazoo River based on
the mean of lipid-normalized total PCBs and TEQSWHQijan .................................... 62

Table 3.1. Mean (i SD) concentrations of total PCBS and 2,3,7,8 —tetrachlorodibenzo-p—
dioxin equivalents (TEQs) in the tissues of terrestrial passerine species at the Fort Custer
State Recreation Area (F C) and at the Trowbridge Impoundment (TB) (Neigh et al.,
2004b) ........................................................................................................................ 89

vii

Table 3.2. Nest fate and percent of initiated nests of eastern bluebirds and house wrens at
the Fort Custer State Recreation Area (F C) reference site and at the Trowbridge (TB)
contaminated site ....................................................................................................... 92

Table 3.3. Eastern bluebird and house wren nest productivity measurements (mean :1: SD)
at a reference site (Fort Custer) and at a PCB contaminated target site (Trowbridge) on
the Kalamazoo River for early and late clutches and all clutches combined ............. 96

Table 3.4. Mean (:1: 1 SD)a reproductive endpoints for eastern bluebird and house wren
eggs and nestlings reared at the Fort Custer State Recreation Area and at the Trowbridge
Impoundment along the Kalamazoo River Area of Concern ..................................... 99

Table 3.5. Power (1 -B) to detect a decrease in reproductive success at Trowbridge
compared to Fort Custer and the sample size (N) needed at each location to detect a 20%
reduction in reproductive health ................................................................................ 107

Table 4.1. Toxicity reference values based on the no observed adverse effect level
(N OAEL) for tissues of avian species at the Kalamazoo River ................................. 129

Table 4.2. Mean concentrations of total PCBS (i 1 SD) and lipid content (3: 1 SD) of
eastern bluebirds and house wrens at the Fort Custer reference area and the Trowbridge
Impoundment at the Kalamazoo River Area of Concern ........................................... 132

Table 4.3. Mean 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) (i 1 SD) and
relative potency (i 1 SD) in eastern bluebird and house wren tissues sampled from the
Fort Custer Reference location and the former Trowbridge Impoundment .............. 135

Table 4.4. Ratios of accumulation between life stages of the eastern bluebird and house
wren based on the mean lipid-normalized total PCBS and TEstnonwian eggs and live
sampled nestlings at the Fort Custer State Recreation Area (F C) and the Trowbridge
Impoundment (TB) ................................................................................................... 139

Table 4.5. Bioaccumulation factors for wet weight concentrations of total PCBS and
2,3,7,8 —tetrachlorodibenzo-p-dioxin (TEQ) in the diet (average potential daily dose)
(Neigh et al. 2004c) to bird tissues at the Fort Custer State Recreation Area (FC) and the
Trowbridge Impoundment (TB) ................................................................................ 146

Table 5.1. Toxicity reference values based on the no observed adverse effect level
(NOAEL) and lowest observed adverse effect level (LOAEL) for dietary exposure of
avian species to PCBs at the Kalamazoo River ......................................................... 171

Table 5.2. Concentration of total PCBS and TEstmy/Wian calculated for dietary exposure

in avian species at the Kalamazoo River based on a site-specific diet and a literature—
derived diet ................................................................................................................. 179

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Figure 1.1. Map of the Kalamazoo River Area of Concern (KRAOC) and reference site.
The inset describes the location of the two counties in Michigan where reproductive
studies were conducted. A box designates the boundaries of the upstream reference
location (Fort Custer State Recreation Area) and the Trowbridge Impoundment, located
within the KRAOC .................................................................................................... 6

Figure 1.2. Percentage of the total population in each year represented by each female age
class at the Fort Custer (F C) reference location and the Trowbridge (TB) contaminated
location ....................................................................................................................... 13

Figure 1.3. Tree swallow (TRSW) nestling growth curves for Fort Custer (FC) reference
site and Trowbridge (TB) target site based on mean nestling mass for each
nest box ..................................................................................................................... 22

Figure 2.1. Kalamazoo River Area of Concern (KRAOC) and reference site ......... 47

Figure 2.2. Contribution of selected congeners to total TEQ in egg, nestling, and adult
samples fi'om the Fort Custer reference site and the Trowbridge Impoundment ...... 60

Figure 2.3. Kalamazoo River hazard quotients based on the no observed adverse effect
level (NOAEL) and the lowest observed adverse effect level (LOAEL). Each box
encompasses the 95% CI about the mean .................................................................. 65

Figure 2.4. The percent contribution of selected congeners and congener co-elution
groups to the concentration of total PCBs in egg, nestling, and adult tree swallows at the
Trowbridge Impoundment ......................................................................................... 73

Figure 3.1. Map of the Kalamazoo River Area of Concern (KRAOC) and reference site.
The inset describes the location of the two counties in Michigan where reproductive '
studies were conducted. A box designates the boundaries of the upstream reference
location (Fort Custer State Recreation Area) and the Trowbridge impoundment, located
within the KRAOC .................................................................................................... 87

Figure 3.2. House wren nestling growth curves based on mean nestling weights for each
nest box at the Trowbridge (TB) target area and the Fort Custer (F C) reference site. The
equation for the line of best fit at PC is y=5.563Ln(x)-2.4223, r2=0.836. The line of best
fit for TB is y=5.378Ln(x)-2.1186, r2=0.896 ............................................................. 101

Figure 3.3. Eastern bluebird nestling growth curve based on mean nestling weights in
each active nest box at the Trowbridge (TB) target site and the Fort Custer (FC) reference
site. The line of best fit for the curve is described by the equation y=13.668Ln(x)-8.8892,
r2=0.647 at TB and y=12.891Ln(x)-4.7993, r2=0.861 ............................................... 102

Figure 4.1. Map of the Kalamazoo River Area of Concern (KRAOC) and reference site.
The inset describes the location of the two counties in Michigan where studies were
conducted. A box designates the boundaries of the upstream reference location (Fort

Custer State Recreation Area) and the Trowbridge Impoundment, located within the
KRAOC ..................................................................................................................... 124

Figure 4.2. Contribution of individual non-ortho and mono-ortho congeners to total
2,3,7,8 TCDD equivalents (TEQs) in the tissues of passerine species at the Fort Custer
State Recreation Area (FC) and the Trowbridge Impoundment (TB) ....................... 138

Figure 4.3. Hazard quotients (HQ) for concentrations of total PCBS and 2,3,7,8 TCDD
equivalents (TEQs) based on the no observed adverse effect level (NOAEL) for house
wrens and eastern bluebirds at the Trowbridge Impoundment. Error bars indicate the
upper 95% confidence limit ....................................................................................... 150

Figure 5.1. The PCB contaminated Trowbridge Impoundment within the Kalamazoo
River Area of Concern and an upstream reference location at the Fort Custer State
Recreation Area ......................................................................................................... 165

Figure 5.2. Comparison of mass gained per day of life for nestlings in nests from which
boluses were collected (bolus) or not collected (no bolus) at the
Kalamazoo River ....................................................................................................... 167

Figure 5.3. Dietary composition based on occurrence at the Kalamazoo River ........ 176

Figure 5.4. Passerine bird dietary hazard quotients for the Trowbridge Impoundment
(Kalamazoo) based on the total PCB no observed adverse effect level (NOAEL) and the
lowest observed adverse effect level (LOAEL). Dietary hazard quotients were calculated
based on the Kalamazoo site-specific diet and literature-derived diets. Error bars
represent the upper 95% confidence limit ................................................................. 182

Figure 5.5. Passerine bird dietary hazard quotients for the Trowbridge Impoundment
based on the TEQWHGAvim no observed adverse effect level (N OAEL) and the lowest
observed adverse effect level (LOAEL) based on toxicity reference values calculated
from the literature. Dietary hazard quotients were calculated based on the Kalamazoo
site-specific diet and literature-derived diets. Error bars represent the upper 95%
confidence limit ......................................................................................................... 184

Figure 5.6. Comparison of literature-derived dietary composition (wet weight) to the site-
specific diet (wet weight) for eastern bluebirds, tree swallows, house wrens, and
American robins at the Trowbridge Impoundment on the Kalamazoo River ............ 186

Figure 5.7. Multiple lines of evidence used to assess risk in Kalamazoo River passerine
species ........................................................................................................................ 193

KEY TO ABBREVIATIONS

Dry weight ............................................................................. dw
Fort Custer State Recreation Area ......................................... FC
Kalamazoo River Area of Concern ....................................... KRAOC
Number .................................................................................. n
Polychlorinated biphenyl ....................................................... PCB
Standard deviation ................................................................ SD
Trowbridge Impoundment .................................................... TB
2,3,7,8 -tetrachlorodibenzo-p-dioxin .................................... TCDD
2,3,7,8 -tetrachlorodibenzo-p-dioxin equivalents ................. TEQ
Wet weight ............................................................................ ww
Part per billion ....................................................................... ppb
Units of measure

Kilogram ................................................................................ kg
Gram ...................................................................................... g
Milligram ............................................................................... mg
Microgram ............................................................................. pg
Nanograrn .............................................................................. ng
Picogram ................................................................................ pg
Days ....................................................................................... (1
Hours ...................................................................................... h
Years ...................................................................................... yr

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Chapter 1
Productivity of tree swallows (T achycineta bicolor) exposed to PCBS at the Kalamazoo

River Superfund Site

Arianne M. Neighf Matthew J. Zwiemik,;r Monica A. MacCarroll,;r John L. Newsted, *1

Alan L. Blankenship, I: Paul D. Jones, I: Denise P. Kay,I John P. Giesy,+§

IZoology Department, Center for Integrative Toxicology, National Food Safety and

Toxicology Center, Michigan State University, E. Lansing, MI 48824

tENTRIX, Inc., Okemos, MI 48864

§Biology and Chemistry Department, City University of Hong Kong, Kowloon, Hong

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ABSTRACT

A 123 km stretch of the Kalamazoo River in Michigan, USA, was designated a
Superfund site in 1990 due to historical releases of effluent containing polychlorinated
biphenyl (PCB) contaminated paper waste. Risk to bird species in the river ecosystem
was evaluated using the tree swallow (T achycineta bicolor) as a monitor for possible
effects due to PCB exposure at nesting locations. There were no statistically significant
differences in hatching success, fledging success, productivity, predicted brood size,
predicted number of fledglings, or growth of nestlings between the Kalamazoo River
Superfund Site and an upstream reference location with lesser concentrations of PCBS in
the sediments and riparian soils. However, in two of the three years of the study, clutch
size at the contaminated location was 3.7 :1: 1.4 and 4.8 i 0.73 eggs per nest (mean :1: SD),
which was significantly less than the clutch size at a reference location (5.0 :t 1.1 and 5.3
i 1.1 eggs per nest). The results of this study indicate that tree swallows exposed to
PCBS in the Kalamazoo River may have decreased clutch size, but productivity and
recruitment were not statistically different between sites. Therefore, tree swallow
populations in the contaminated area had overall reproductive success that was not
impaired by exposure to PCBs at a level that overcame the natural variation inherent in

tree swallow populations.

Keywords: Reproductive success, Polychlorinated biphenyls, Aquatic food chain, Birds

INTRODUCTION

In 1990, 123 km of the Kalamazoo River in southwest Michigan was designated a
Superfund site based on the presence of polychlorinated biphenyls (PCBS) in multiple
matrices including fish, sediments, and floodplain soils. PCBS have been linked to
adverse effects in numerous avian species (Giesy et al., 1994). These effects include
reproductive dysfunction (Dahlgren et al., 1972; Britton and Huston, 1973; Lillie et al.,
1974; Ludwig et al., 1993; Halbrook et al., 1998) , embryonic deformities (Ludwig et al.,
1993; Summer et al., 1996), and growth impairment (Lillie et al., 1974; Ludwig et al.,
1993). As part of this multiple lines of evidence approach, we evaluated the effects of
PCBs on behavior and productivity of resident tree swallow populations on the

Kalamazoo River.

Passerine birds, particularly tree swallows (T achycineta bicolor), have been effectively
utilized as monitors of exposure to environmental contaminants. The tree swallow has
been frequently used as a contaminant monitor in North American riverine and lacustrine
systems, which has resulted in a large information base on accumulation of PCBS by tree
swallows including bioavailability, diet, tissue concentrations, and subsequent effects on
reproduction and reproductive behavior (Ankley et al., 1993; Jones et al., 1993; Froese et.
al., 1998; Bishop et al., 1999; McCarty and Secord, 1999; Harris and Elliott, 2000;
Custer et al., 2003). The tree swallow has even been termed a “new model organism” for
its frequency of use and favorable life history traits (Jones, 2003). In this study, the tree

swallow was selected as a representative for passerine species exposed to sediment-

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derived PCBS through the aquatic food chain because of a number of distinct attributes
including the presence of a previously established nest box population at the baseline
location; an abundance of tree swallows residing throughout the river basin; and a large
database of information on similar PCB exposure and productivity studies. As a PCB
tolerant species, the tree swallow is a useful monitor of PCB contamination (McCarty and
Secord, 1999). The tree swallow also has a small feeding range of approximately 0.1 km
(McCarty and Winkler, 1999) to 5 km (Robertson et al., 1992) during the nesting period,
which assures that pairs nesting near the river will feed on prey that are in direct contact
with PCB-contaminated sediment. Tree swallows are insectivorous, typically feeding on
emergent aquatic insects just above the water surface (Quinney and Ankney, 1985;
Cohen and Dymerski, 1986; McCarty, 1997). Tree swallows readily nest in boxes and
are tolerant of human disturbances during nesting (Rendell and Robertson, 1990).
Researchers have used tree swallows for a variety of studies without a notable occurrence

of observer-induced abandonment.

Concentrations of PCBS were significantly greater in tree swallow eggs and nestlings
within the Kalamazoo River Superfund Site, as compared to concentrations in birds from
an upstream reference location (Neigh et al., 2004). The risk of PCB-induced effects was
determined by comparing site-specific measured concentrations of PCBs in bird tissues to
toxicity reference values (TRVs) determined in controlled laboratory studies with
surrogate species (Neigh et al., 2004). However, extrapolating from laboratory
experiments to tissue concentrations observed in the field has inherent uncertainties

(USEPA, 1998). Thus, in conjunction with the tissue-based assessment of risk, this study

 

 

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monitored tree swallow reproductive and developmental health on the Kalamazoo River
directly by measuring population-level responses, including fecundity, fertility, and
weight gain of nestling tree swallows exposed to PCBS in their diet, from contaminated

sediments and riparian soils.

MATERIALS AND METHODS

Site details

Two sites within the Kalamazoo River floodplain were selected to study nesting tree
swallows, the Fort Custer State Recreation Area (FC) and the former Trowbridge
impoundment (TB) (Figure 1.1). The FC reference or baseline location is situated 48 km
upstream of known sources of PCBS between the villages of Augusta and Galesburg in
southwest Michigan. The site, which is comprised primarily of sandy oldfield grasslands
interspersed with maple-beech forest, was the most similar to the TB impoundment in
habitat and proximity to the river’s course. Michigan State University and the
Kalamazoo Nature Center have conducted nest box studies on the site for the last 30 yr,
and the tree swallow population has demonstrated normal levels of reproductive success

(R. Adams, personal communication).

 

 

 

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Figure 1.1. Map of the Kalamazoo River Area of Concern (KRAOC) and reference site.
The inset describes the location of the two counties in Michigan where reproductive
studies were conducted. A box designates the boundaries of the upstream reference
location (Fort Custer State Recreation Area) and the Trowbridge Impoundment, located

within the KRAOC.

Concentrations of PCBS and 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQS),
based on World Health Organizations toxic equivalence factors for birds (TEFWHQBird)
(van den Berg et al., 1998), in tissues of tree swallows at the FC reference location are
reported elsewhere (Neigh et al., 2004). The following concentration data are from the
reference location and are reported on a wet weight (w) basis. Mean concentrations of

PCBS and TEQs in eggs were 810 ng PCB/g (ppb), (n = 19) and 56 pg/g, (n = 12),

respectively. Mean concentrations of PCBS and TEQS in nestlings were 460 ng PCB/g,
(n = 12) and 20 pg TEQ/g, (n = 12), respectively. Mean concentrations of PCBS and

TEQS in adults (n = 2) were 1500 ng PCB/g and 220 pg TEQ/g, respectively.

The target study area (TB) is located upstream of the former Trowbridge Darn
Impoundment near Allegan, MI. The study area was wholly within the Kalamazoo River
Area of Concern (KRAOC), which is designated as a Superfund site by the US
Environmental Protection Agency. The TB dam was removed to its sill in 1986, which
resulted in the exposure of a large and contiguous landmass of former lake bottom, on
which nest boxes were established. The former Trowbridge impoundment includes
approximately 132 ha of currently exposed former sediments flanking 7 km (70 ha) of
remaining impounded water. The TB study area is approximately 67 km downstream
from the reference area and was considered a worst case scenario for exposure to
wildlife. The former sediments have been minimally developed, so the extensive
floodplain remains under natural vegetation of lowland forest, wet grassland, lowland
shrub, and emergent marsh. Mean concentrations of total PCBS in eggs, nestlings, and
adults were 5100 (n = 14), 3100 (n = 13), and 8700 ng PCB/g (n = 9), ww, respectively
(Neigh et al., 2004). The presence of non-ortho and mono-ortho PCB congeners,
reported as TEQWH0-Bi,d, were found to be 760 (n = 12), 600 (n = 13), and 2200 pg TEQ/g

(n = 9), w in eggs, nestlings, and adults, respectively (Neigh et al., 2004).

Prutizctr
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Productivity and attentiveness observations

In April 2000, nest boxes were placed at both the former Trowbridge Darn Impoundment
(TB) and the Fort Custer State Recreation areas (F C). At the F C site, nest boxes (n = 38)
had been previously established during long-term studies, but an additional 26 boxes
were added for a total of 64 nest boxes. The 2000 field season was the first year boxes
were available for nesting throughout the TB area (n = 68), so occupancy rates at this site
were expected to be less than the established F C site. For this reason, 2000 was
designated a baseline year to establish nesting populations in the newly placed boxes at
both FC and TB. The establishment and weathering of boxes in 2000 was intended to
improve the correlation of data gathered from individuals nesting in the newly erected

boxes and individuals utilizing the previously established nest boxes at the FC site.

Nest boxes were selectively placed in open/prairie grassland habitats to increase
occupancy rates by secondary-cavity nesting passerine species. All boxes were placed
within the floodplain, not more than 200 m from the river. Two types of boxes with
different dimensions were placed on greased metal poles. One set of spruce-pine-fir-
constructed boxes had internal dimensions of 10 x 14 x 23 cm, while cedar-constructed
boxes had internal dimensions of 8 x 18 x 40 cm. Wire mesh predator guards surrounded
the entrance hole and extended 6 cm from the box. Beginning in early April, boxes were
checked every third day for the initiation of nest building. Once nest construction was
complete, the nest was checked daily to determine date of clutch initiation, which was
reported as Julian days. Within 24 h of laying, the mass and length of eggs were

recorded, and each egg was given a unique identification code with a permanent marker.

 

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Clutch size was determined as the total number of eggs laid by a single female.
Incubation was determined by touch. Warm eggs indicated incubation, while nests with
no defending adults and cold eggs for 7 d were considered abandoned. Upon completion
of the clutch, the nest was checked every few days until the end of the 14-d incubation
period, at which time, the nest was again examined daily to determine day of hatch. Day
of batch was also confirmed by assessing physical development of the nestling. Each
nestling was examined for gross morphological abnormalities. With hatch day
designated as day 0, weight of each nestling was recorded on days 3, 9, and 12 as an
approximation of growth. Nestling body measurements were also used to approximate
growth. On day 12, chicks were weighed and the length of the entire body (tip of beak to
longest retrix), tarsus (tibiotarsal joint to bind toe base), and unflattened wing chord were
recorded. The sex of individual nestling tree swallows could not be determined due to
the nestling’s sexually dichromatic plumage, but when possible, female age was

determined according to plumage characteristics described by (Hussell, 1983).

The study’s sampling design, in which eggs were removed after clutch completion for
residue analyses, prevented the brood size (number of nestlings at hatch) and the number
of fledglings from being determined directly, so we calculated a predicted brood size and
number of fledglings based on reproductive success measurements. Predicted brood size
was calculated as the product of the clutch size and hatching success. The number of
fledglings was calculated as the clutch size multiplied by the productivity, which is a
product of hatching and fledging success. Hatching success was determined as the

number of nestlings at the time of hatching per egg laid. Sampled eggs were excluded

 

 

 

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from the analyses because the viability of the eggs was unknown at sampling. Fledging
success was determined as the number of fledglings divided by the number of nestlings at
the time of hatch. It was assumed that all nestlings taken live would have fledged and
that all nestlings at the latest nest check had fledged, unless their carcasses were found.

One fresh egg or one live nestling was sampled from each nest.

Parental attentiveness of tree swallow adults was assessed during 30-min observation
sessions of the nest box. The number of visits by the adults is correlated with the number
of feedings (McCarty, 2002). On day I through 17 of the nestling period, each box was
observed for a minimum of 3 sessions to determine the approximate number of times the
adults fed the nestlings. Observations took place during the most active feeding periods
between 08:00-12:00 and 18:00-21 :00. The number of visits per nestling were averaged
over all observations for a box in order to minimize the effect of nestling age and to avoid
pseudoreplication. Average nestling age at both locations during nest observations were

9, 8, and 10 days for 2000, 2001, and 2002, respectively.

Statistical Analyses

Meristic data were examined by a combination of parametric and nonparametric
statistical procedures, depending on the structure of the data. The normality of each
sample set was assessed with the Kolmogorov-Smimov one sample test with Lilliefor’s
transformation. Data sets that were determined to have normally distributed values were
compared by Student’s t-test, or in the case of multiple comparisons, by a one-factor

analysis of variance (ANOVA). Data with non-normal distributions and/or unequal

 

 

 

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variances were analyzed by Mann-Whitney U or Kruskal-Wallis non-parametric tests for
two or multiple samples. All data, regardless of normality and homogeneity of variance,
was evaluated for interaction with cofactors based on an analysis of covariance
(ANCOVA). Although the assumption of normality was violated in some instances, we
do not believe that ANCOVA based on the ranks would have been a more reliable
estimate of interaction because of the loss of discriminatory ability inherent in the

ranking process. The criterion for significance used in all tests was p < 0.05.

Measurements from some nests were excluded from analysis after a disturbance, but
measurements taken before the disturbance were included. Several nests were excluded
after predation, which was determined by the presence of house wrens near the nest box
or when the nest material was disturbed. Abandoned nests were included in the
calculation of hatching success, fledging success, and productivity until the point where

they were abandoned.

RESULTS

Reproductive success

The mean number of clutches initiated during the study was greater at the Fort Custer
State Recreation Area than at the Trowbridge Impoundment. During the three-year study
period, 34 clutches were initiated at the TB target site and 71 clutches were initiated at
the FC reference site. At TB there were 9, 12, and 13 clutches initiated during 2000,

2001, 2002, respectively, and 20, 24, 27 clutches initiated during the same three-year

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period at F C. Female age was evaluated at each nest during 2001 and 2002 to address the
influence of adult age on reproductive parameters such as clutch size and date of clutch
initiation. There was a difference between years in the proportion of second year (SY) to
after second year (ASY) females during 2001 (Mann-Whitney U, p = 0.038) but not
during 2002. SY females were in their first breeding season and ASY females were in at
least their second breeding season. TB had a greater number of SY birds during 2001
compared to 2002 and compared to FC during both years (Figure 1.2). Female age was
not a statistically significant cofactor for any reproductive parameters (ANCOVA, p >

0.05).

12

 

 

Figure

Class a:
location
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(Mann-l
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8 2001 2002 2001 2002

Fort Custer Trowbridge

Figure 1.2. Percentage of the total population in each year represented by each female age
class at the Fort Custer (FC) reference location and the Trowbridge (TB) contaminated
location.

aMean female age was significantly different from the Fort Custer reference population
(Mann-Whitney U, p = 0.038).

I’After second year (ASY) birds were in at least their second breeding season.

cSecond year (SY) birds or subadults are in their first breeding season.

Tree swallows produce a single brood annually, but may renest when nests are predated
(Kuerzi, 1941). Several incidences of renesting were probable at FC. For one nest box, a
pair appeared to have raised two successful broods for two consecutive years, but this
was not confirmed since the adults were not captured for banding. All nesting attempts

were assumed to be independent events because adults were not banded at PC or TB.

 

 

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nest failures

Clutch size differed significantly between years at each site, so years were analyzed
separately. Mean clutch size at FC was significantly greater than at TB during 2000 and
2002 (Mann-Whitney U, p < 0.05) (Table 1.1). Date of clutch initiation was a significant
covariate with clutch size in 2000 and 2001 but not 2002. Even when date of initiation
was included as a co-factor, clutch size was still not significantly different between sites
in 2001. All data sets violated assumptions of normality, and therefore, were evaluated
by nonparametric tests. No measures of productivity, besides clutch size, were
significantly different between sites in any year. The predicted number of nestlings and
predicted number of fledglings were also not significantly different between sites in any
year (Mann-Whitney U, p > 0.05). Although non-normal distribution prevented
parametric tests, female age and date of clutch initiation were evaluated for covariation
with reproductive parameters. They described some of the variation in the data sets, but
no cofactor interacted with reproductive parameters to such a degree that the significance
of the test statistic changed. The majority of nest failures at F C during 2002, and over the
course of the study, were due to competition by house wrens. At TB, about 57% of the

nest failures were due to abandonment and 14% to predation (Table 1.2).

 

 

 

 

 

 

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Table 1.2. Nest fate and percent of total nests initiated at the Fort Custer (FC) reference

site and the Trowbridge (TB) target site for nests in which eggs were laid.

 

 

3.999. 119.1 2.992.
FC TB FC TB FC TB
# Successful nestsa l9 7 21 9 17 ll
(95%) (78%) (88%) (75%) (63%) (85%)
# Abandonedb 1 2 1 o o 2
(5%) (22%) (4%) (0%) (0%) (15%)
# Predatedc 0 0 1 1 9 0
(0%) (0%) (4%) (8%) (33%) (0%)
# Other“ 0 o 1 2 1 o
(0%) (0%) (4%) (17%) (4%) (0%)
Total # initiated 20 9 24 12 27 13
(100%) (100%) (100%) (100%) (100%) (100%)
Total # of boxes 64 68 64 68 64 68

available

Wests in which at least one nestling fledged.

bNests containing eggs and/or nestlings but without an adult present for at least 7 d.
cNests had signs of disturbed nest material or had evidence of tossed or damaged eggs
attributable to house wren competition.

dNests with an unknown fate or failed due to disease.

Mean egg lengths and weights are presented for each location (Table 1.3). Mean egg
length and weight exhibited a statistically significant interaction (ANCOVA, weight x
length p < 0.001), but the interaction with clutch size was not significant. There were no
significant differences between years at either site, so measurements were combined for
multiple years. Average egg weight was significantly greater at TB than FC (Mann-
Whitney U, p = 0.006). Average length of the eggs was not significantly different

between locations.

 

 

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Old

Hm
Bm

Tar

Table 1.3. Mean (SD)3 reproductive endpoints for tree swallow eggs and nestlings (12-d-
old) reared at the Fort Custer State Recreation Area and at the Trowbridge Impoundment

along the Kalamazoo River Area of Concern.

 

 

Fort Custer Trowbridge

Eggs

N 71 34

Egg weight (g) 1.80 (0.02) 1.86 (0.15)”

Egg length (mm) 19.0 (0.8) 19.0 (0.7)
Nestlings

N 13 8

Body weight (g) 22.12 (1.47) 22.37 (1.87)

Body length (mm) 93.8 (8.6) 90.8 (6.0)

Tarsal length (mm) 13.3 (1.9) 13.7 (2.7)

Wing chord (mm) 49.9 (11.0) 50.9 (5.7)

 

8Mean values were calculated based on the mean measurements per nest for all nests with
eggs or nestlings present during the entire study period from 2000 to 2002.
I’Mean was significantly different from the Fort Custer reference population (Mann-

Whitney U p=0.006).

Date of clutch initiation was significantly different among years at both sites (Kruskal-

Wallis, p < 0.05) and was significantly different between sites during 2001 and 2002

 

 

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(Mann-Whitney U, p > 0.05). Median clutch initiation dates were generally earlier at TB
than at F C, but the range of dates over which nests were initiated was later at FC. For all
years, clutches initiated more than i 1 SD from the mean at a site were designated as
early or late nesters. A total of 7 nests at TB and 13 nests at PC were beyond the cutoff
dates during the three-year study period. Upon recalculation of reproductive success to
exclude outlying early and late nesters, only the significance of clutch size between sites
changed in 2002 (p = 0.032 to p = 0.082). Thus, differences in clutch initiation dates did

not significantly affect the conclusions about other parameters.

Growth and growth curves

Growth parameters of mean weight, tarsal length, wing chord length, and body length for
sampled nestlings (12 d) were not significantly different between sites when all sample
years were combined (Table 1.3). Differences between years could not be evaluated due
to small sample sizes. When growth parameters were evaluated for covariation, body
length and wing chord variances were significantly associated, but this did not change the

significance of mean growth parameters between sites.

There were few differences in average mass of nestlings between locations when years
were combined. Mean nestling mass was greatest on day 11 at both sites. Nestlings at
TB weighed more at day 3, although not significantly, but weights between the two sites
were very similar by day 11 (Table 1.4). There were no statistically significant
differences in nestling weights between sites, except on day 13 when TB nestlings were

significantly heavier than FC nestlings (Student’s t-test, p = 0.044). There were

19

statistically significant differences between years, so sites were also compared within
each study year. When sample sizes were sufficient to make comparisons, no
comparisons were significant, except nestlings at TB were heavier than F C nestlings on

day 5 in 2001 (Student’s t-test, p = 0.041).

Table 1.4. Tree swallow nestling weight (g) expressed as the mean nestling weight in
each nest at the upstream Fort Custer reference area and the former Trowbridge

Impoundment from 2000 to 2002.

 

 

 

Fort Custer Trowbridge

N Mean (SD) N Mean (SD)
Nestling day
2 4 4.71 (0.46) 2 4.11 (0.14)
3 34 5.81 (1.60) 17 6.26 (1.55)
4 7 8.45 (2.18) 4 8.63 (2.78)
5 4 8.52 (1.70) 3 10.97 (2.50)
6 3 14.28 (0.92) 1 13.72 (NA)
7 4 17.80 (3.96) 3 16.99 (3.12)
8 2 18.75 (1.84) 4 19.59 (2.63)
9 40 20.31 (1.97) 17 19.55 (1.77)
10 7 21.95 (2.64) 4 22.27 (1.69)
11 7 22.97 (0.94) 6 22.96 (0.98)
12 43 22.15 (2.34) 12 22.01 (1.06)
13 8 22.80 (1.16) 5 24.08 (0.60)‘

 

3Significantly different from reference location (Student’s t-test, p = 0.044).

NA= Not Available

Over the nestling period at each location, logistic growth curves were fitted to the
average nestling mass in each box across all nests. Curves based on a logistic model
have been shown to be the most appropriate for describing nestling growth in tree

swallows (Zach and Mayoh, 1982). Growth curves were virtually identical between sites

20

 

 

and am
and 0.9
based (
Nestling
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dit‘i‘crcn

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and among years (Figurel.3). Logistic growth curves yielded R2 values of between 0.90
and 0.93 for the tree swallow. Growth curves between sites were statistically compared
based on average nestling mass gain from day 3 to day 10 over the nestling period.
Nestling masses were log-transformed, and the mass gain, calculated as the mass gained
per day of life, was compared between sites. There were no statistically significant
differences in mass gain between sites in any year (Student’s t-test, p > 0.05) or when all

years are combined (Mann-Whitney U, p = 0.368).

21

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Parental attentiveness

At the Kalamazoo River, a total of 127 h of feeding observations were made during a 3-
yr period. In order to minimize the effect of brood size on parental attentiveness, the
number of visits per 30-min period was normalized to the number of nestlings in each
nest. Years were analyzed separately because the mean number of visits per nestling was
significantly different between years at TB (ANOVA, p = 0.002). When the covariates
time of observation, nestling age, and date of observation were factored into the model to
compare among years within each site, 2002 remained significantly different from other
years at TB (ANCOVA, p = 0.023). The mean number of visits per nestling was not
significantly different between sites for either 2000 or 2001. However, the number of
visits per nestling was significantly different in 2002 (Student’s t-test, p = 0.006). TB
had a mean number of visits per nestling of 0.49 i 0.37 (i1 SD) while the mean number
of visits for F C was 1.00 :1: 0.44 (i1 SD) in 2002. Weather does not appear to have been
a factor explaining this difference because the times and dates of observation were
randomly dispersed between sites. No interactions with time, nestling age, or date of

observation were significant in any analysis between sites.

Gross morphology and abnormalities
Upon examination of the external morphology of nestlings and contents of eggs, no
external developmental abnormalities were observed at any site during any sampling

year.

23

DISCUSSION

Reproductive success

Fewer clutches were expected at TB than FC because F C has had a nesting population
established for 30 yrs with adults 5and offspring returning to nest annually (Kuerzi, 1941;
Cohen et al., 1989; Robertson et al., 1992). The number of nests established by adults
increased at TB as the study progressed, probably due to the return of birds raised on the
site in previous years. Unfortunately, we could not determine the proportion of returning
birds in the population because nestlings were not banded. The increase in the number of
nesting tree swallows at PC during the course of the study may be a result of the
establishment of additional nest boxes at PC during 2000. In addition to the increase in
nest establishment, the number of ASY females at TB increased from 2001 to 2002. The
large number of SY females during 2001 at TB may be a result of establishing a new nest
box trail in 2000 (Robertson et al., 1992). We have dismissed the possibility that the
large juvenile population in 2001 was due to PCB-induced reduction in adult survival
during 2000. In this study, reproduction, the most sensitive response to PCB exposure
measured, was not different from that at the reference site. Thus, it can be concluded that

exposures to PCBs were not sufficient to cause population-level effects on tree swallow

adults at the KRAOC.

Age of females has been identified as an important factor in tree swallow reproduction.
SY birds may have lesser reproductive output due to lack of breeding experience

(Wheelwright and Schultz, 1994; Saether, 2003). These factors may contribute to smaller

24

 

clutches and lesser productivity in SY birds during portions of the nesting season (De
Steven, 1978; Wheelwright and Schultz, 1994; Stutchbury and Robertson, 1988).
Although there was a statistically significant difference in female age between years and
sites, it is unlikely that reproductive success was affected by the age of the females, since
all reproductive parameters were evaluated for covariance with female age and no
interaction was significant. This suggests that female age had little effect on the outcome

of reproduction at sites along the Kalamazoo River.

Date of clutch initiation was also considered as a possible cofactor with reproductive
success of tree swallows (Stutchbury and Robertson, 1987; Stutchbury and Robertson,
1988; Winkler et al., 2002). Adults who initiate earlier tend to have larger clutches than
adults who initiate later in the season, which translates into larger broods and more
fledglings from early nesting adults (Stutchbury and Robertson, 1988). This relationship
may not be due to direct interaction between date of initiation and clutch size, but may be
due to other confounding factors (Winkler et al., 2002). Nest initiation may be
constrained early in the season due to low temperatures (Kuerzi, 1941; Stevenson and
Bryant, 2000; Winkler et al., 2002), but adults who nest early may obtain prime nesting
locations before other adults arrive at the site (Stutchbury and Robertson, 1988). Early
nesters may also benefit from coincidental timing of temperature-dependent insect
emergence during the nestling period (Stevenson and Bryant, 2000). Timely nesting is
beneficial to the grth and development of the nestlings and overall reproductive
success because nesting coincides with insect prey abundance during the peak growing

period of the nestlings (Quinney et al., 1986). In our studies, there was no interaction

25

between overall productivity and date of initiation, but clutch size did significantly
interact with date of initiation in 2000 and 2001. The relationship between reproduction
and earlier nest initiation at TB could possibly have offset some effects induced by PCBs,
but effects caused by PCBs are likely to overshadow interactions with early initiation.
The lack of significant interactions between reproduction and date of nest initiation also
suggests that initiation date does not have a significant role in reproductive outcome at

the Kalamazoo River.

Reproductive success reported as hatching success, fledging success, and overall
productivity, are ecologically important parameters that if affected by exposure to PCBS
could result in population-level effects. These measures of reproduction were similar
between sites and within the normal range for populations as summarized by Robertson
et al. (1992). This suggests that the KRAOC population was not exposed to
concentrations of PCBS that were sufficient to cause adverse effects. The power to detect
differences in the mean between locations was generally insufficient (1 -B < 0.20), and the
power of the analyses was generally insufficient to detect a 20% reduction in
reproductive health at TB compared to FC (Table 1.5). Much of the loss of power is
likely attributable to the variability associated with reproductive measurements, but
insufficient sample sizes also contribute to the inability to detect differences. For some
instances, the power was exceptionally low because the calculated mean at TB was
greater than the mean at F C, which was the reverse of the alternative hypothesis.
Although power may have been low for statistical tests comparing mean reproductive

measurements between locations, the reproductive success of both the FC and TB

26

population were generally within the normal range reported for other tree swallow

populations (Robertson et a1. 1992).

Table 1.5. Power (l-B) and sample size (N) needed to detect a 20% reduction in

reproductive success at the Trowbridge Impoundment compared to the Fort Custer State

 

 

Recreation Area.
M9 ;_00_1 2902 All Years
Min—mi.
1-8 N 1-0 N H) N 1-0 N
Hatching success 0.15 62 0.01 28 0.15 61 0.15 48
Fledging success NA NA 0.01 8 <0.01 5 0.01 5
Productivity 0.15 62 0.01 37 0.10 68 0.11 55
Clutch size 0.80 20 0.05 8 0.52 g 10 0.85 13

Predicted brood size 0.17 33 0.05 27 0.07 46 0.24 32
Predicted number of 0.17 33 0.03 28 0.03 54 0.15 36

fledglings

 

NA= Not Available

The reproductive endpoint measured in this study that exhibited a statistically significant
difference between locations in some years, was clutch size. In two out of three years,
the clutch size was greater at the reference location than at TB in the KRAOC. However,

clutch size at both the F C and TB locations along the Kalamazoo River were slightly less

27

than those reported for other populations (unweighted grand mean (i SD) for 28
populations = 5.40 (0.37)) (Robertson et al., 1992). Other studies where tree swallows
have been exposed under field conditions to concentrations of PCBs that were similar or
greater than those at the KRAOC did not exhibit effects on clutch size that could be
related to exposure to PCBs (Custer et al., 1998; Custer et al., 2003). At some locations
with elevated concentrations of PCBS, such as Hudson River, a greater incidence of
supernormal clutches was observed (McCarty and Secord, 1999). This phenomenon has
also been documented in gull species in contaminated areas (Conover, 1984). We did not
observe more supernormal clutches at TB, but we did observe 3 clutches at PC with 7

eggs each.

During incubation, it is possible that abandonment may increase due to contamination
(McCarty and Secord, 1999), but there are other factors that can cause abandonment.
There were several incidences of interference by house wrens at both PC and TB and
several cases of abandonment (FC 11 = 2, TB 11 = 4). Over the study period, the
percentage of total nests abandoned at TB (12%) was greater than at PC (3%). Some
adults experienced attacks by house wrens during the incubation stage, and therefore,
some or all of the documented cases of abandonment may be attributed to this disruption
or to inclement weather. Several cases of egg burial were observed at both sites. This
behavior is believed to be a precursor to abandonment (Secord et al., 1999), but in each
case of egg burial at TB, the nest was not abandoned. Although beyond the scope of this

paper, it is possible that the eggs were infertile and subsequently buried by the female to

28

better incubate the remaining fertile eggs. Studies designed to evaluate PCB-induced

infertility and resource partitioning would be needed to further address this hypothesis.

Eggs exposed to PCBs may have a slightly smaller size and mass, but the relationship is
not considered to be strong (Secord and McCarty, 1999). Eggs from the KRAOC, where
adults were exposed to greater concentrations of PCBS, were significantly heavier, but
PCB concentration was not correlated with egg weight or hatchability. Egg weight and
length from TB were within the range for unexposed populations, but egg mass at PC was
slightly less than normal populations (De Steven, 1978; Wheelwright and Schultz, 1994).
In western bluebirds (SiaIia mexicana), exposure to PCBs has been associated with
smaller egg volume, which was mainly associated with variation in egg width (Fair and
Myers, 2002). In contrast, PCB exposure in one study was linked to larger yolk mass in
American kestrels (Falco sparverius) (Femie et al., 2000), which may account for the

significantly heavier eggs at TB.

Growth and growth curves

Growth parameters and nestlings’ weights measured for both sites were within the normal
range for tree swallows (Wheelwright and Schultz, 1994; Harris and Elliott, 2000).
Thirteen days after hatching, tree swallows at TB were slightly heavier than those at F C,
which may be associated with the heavier eggs at TB (St.Louis and Barlow, 1993).
Moreover, other studies have not found a causal link between growth in tree swallows
and PCB exposure (McCarty and Secord, 1999; Harris and Elliott, 2000), although it is

suggested that growth measurements based on weight are suitable indicators of stress

29

(Zach and Mayoh, 1982). The apparently normal growth of tree swallows exposed to
PCBS observed in this study and in other studies suggests that the tree swallow may be

less sensitive than other species (Ludwig et al., 1993).

Growth rates of nestlings were within the range expected for uncontaminated
populations, although mean weights at each day were slightly greater at the Kalamazoo
River than in other populations (Kuerzi, 1941; Harris and Elliott, 2000). Growth curves
for tree swallows on the Kalamazoo River were based on a logistic equation as suggested
by Zach and Mayoh (1982), but the logistic curve underestimated mean nestling weight
for the populations at day 11 and overestimated weight at day 12. The curves fit well
between days 3 and 10. It is suggested that the logistic curve overestimates maximum
mass in nestlings and does not properly model weight recession, but a polynomial model
fits the curves more precisely (Harris and Elliott, 2000). At 12 d of age, the logistic
model underestimated nestling mass, but the data did conform to this function over the
rest of the growth curve. The evaluation of growth recession was beyond the scope of the
study since most nestling weights were not evaluated after 12 d. In this study, the logistic
model seems to be an adequate fit over the portion of the nestling period that was
evaluated. Mass gain per day, which described the slope of the grth curve at
individual boxes, was also not significantly different between sites. The lack of
significant differences in nestling weight at each day and the similarity of growth curves
between FC and TB suggest that there were no PCB related effects on grth of tree

swallow populations within the KRAOC.

30

Deaths“

 

 

 

Farrah
Some
contur
u[.l‘“
Peakall
Pcunlc
Inne.h
1980 l.
nesdins
\‘lSllS \:
be anr
ObScn‘;
rcknior
COl‘dClu
CeTlain

One 01-
““ lht
Pie} 1‘0

decreas

Parental Attentiveness

Some studies have shown that behavior of birds can be altered by exposure to
contaminants, including PCBs (Peakall and Peakall, 1973; Mora et al., 1993; Halbrook et
al., 1998). In doves (Columba livia), there was a decrease in attentiveness (Peakall and
Peakall, 1973), prolonged courtship, and failure to nest when exposed to PCBS (Tori and
Peterle, 1983). Likewise, Forster’s terns (Sterna forsteri) exhibited longer incubation
time, less attentiveness to nests, nest abandonment, and egg disappearance (Kubiak et al.,
1989). Such an effect on attentiveness of the adults, measured as the number of visits per
nestling, was not observed among TB birds in 2000 or 2001, but in 2002 the number of
visits was significantly less at TB compared to FC. The difference between sites can not
be attributed to environmental factors such as weather or time of sampling because
observations took place randomly, and there was no change in the significance of the
relationship when time of observation and age of nestlings were considered as interacting
cofactors. There is some evidence that feeding rates can speed up or slow down during
certain periods (Kuerzi, 1941), and it is possible that observations were conducted during

slow periods in 2002.

One other possible explanation for fewer feeding visits per nestling at TB during 2002
was the likely relationship between large brood size and the ability of adults to capture
prey for the large brood. As brood size increased, the number of feedings per nestling
decreased (Leffelaar and Robertson, 1986). The correlation between visits and the
number of nestlings was examined, and there was only a slight relationship (r2 < 0.20).

This relationship could not account for the observed difference in visitations because

31

brood size at TB during 2002 was smaller than in other years. Tree swallow populations
are believed to respond to insect abundance (Quinney et al., 1986), so one other
explanation for the fewer visits at TB than F C involves the availability of aquatic insects
at TB during 2002. Aquatic insects make up a larger proportion of the diet at TB (A.
Neigh, unpublished data), so if there were fewer insects one might expect fewer visits to
the nest due to the increased prey collection times. While the reason for fewer visits
observed at TB in 2002 is unknown, the fact that such an effect was not observed in every
year suggests that it was not related solely to exposure to PCBs. While it can not be ruled
out that this effect might have been caused by some interaction between exposure to
PCBs and nutritional or climatic factors, this seems unlikely. Regardless of the reason,
the fewer number of nest visits did not result in differences in growth, survival, or overall

productivity. Thus, the observation was not deemed to be ecologically relevant.

Gross morphology and abnormalities

Tree swallows are not particularly sensitive to morphological defects caused by exposure
to PCBs (McCarty and Secord, 1999). This conclusion is supported by the lack of
abnormalities at PCB concentrations greater than the threshold for effects in other species
(Barron et al., 1995). Caspian terns in Saginaw Bay exhibited a range of abnormalities,
including, among others, scoliosis, clubbed feet, and gastrochisis with body
concentrations of 8.0 to 18 ug PCB/g (Ludwig et al., 1993), while tree swallows at the
Hudson River had concentrations up to 62 pg PCB/g, w in nestlings with no

morphological abnormalities (Secord et al., 1999). Kalamazoo River populations did not

32

exhibit any morphological abnormalities at concentrations as great as 32 ug PCB/g

(Neigh et al., 2004).

CONCLUSION

This study is the first report of investigations into the reproductive function of tree

swallow populations exposed to aquatic sources of PCB contamination through the diet at

the Kalamazoo River Superfund Site. Multiple parameters focusing on PCB-induced

effects, including several measurements of reproductive success, growth, and behavior,

were examined in KRAOC tree swallows where tissue concentrations were significantly

greater than at a reference population (Neigh et al., 2004). Reproduction was not

significantly different between the contaminated and reference site with the exception of
clutch size. The difference in clutch size was not observed in all years, and the difference
in clutch size became inconsequential as the nesting season progressed. The most
predictive measures of population recruitment, productivity, and the number of fledglings
were not significantly different between the two locations. Thus recruitment was the
same at both sites. Growth was also similar between sites and was similar to mass gain
rates for other populations. Behavior was also evaluated based on the number of adult
Visits to the nest during the nestling period. There was a significantly greater number of
Visits at PC than at TB during 2002, but the ecological significance of this difference
appears to be minimal. If the number of visits was an ecologically relevant population-
level effect of PCBs, it would have been expected to have led to reduced nestling growth
and oVerall productivity. However, growth and productivity were similar between sites

111 2002, which suggests that this was not an ecologically significant population-level

33

 

response. 8.:
comparisons it

be affected b}

 

 

 

response. Based on three years of observation evaluating multiple parameters and
comparisons to other tree swallow populations, the birds at the KRAOC did not appear to

be affected by exposure to current concentrations of PCBs at the KRAOC.

34

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tems: Reid
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inimn, lit

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lepmducliur
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38

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39

Chapter 2
Tree swallow (T achycineta bicolor) exposure to polychlorinated biphenyls at the

Kalamazoo River Superfund Site
Arianne M. Neigh,? Matthew J. Zwiemik,T Patrick W. Bradley;r Denise P. Kay,I Cyrus S.
Park,“ Paul D. Jones,I John L. Newsted,z Alan L. Blankenship,“ John P.

Giesy,ms

W‘Zoology Department, Center for Integrative Toxicology, National Food Safety and

Toxicology Center, Michigan State University, E. Lansing, MI 48824

IENTRIX, Inc., Okemos, Ml 48864

§Biology and Chemistry Department, City University of Hong Kong, Kowloon, Hong

Kong, SAR, China.

40

ABSTRACT

In 1990, a portion of the Kalamazoo River in Michigan, USA, was designated a
Superfund site due to the presence of polychlorinated biphenyls (PCBs) in the sediment
and floodplain soils. During a four-year period from 2000 to 2003, several avian species
were monitored for reproductive effects and concentrations of PCBs in tissues attributed
to food chain transfer from contaminated sediments. The tree swallow (T achycineta
bicolor) was chosen as a model receptor for contamination of passerine species. A “top-
down” methodology was used to evaluate the bioaccumulation of PCBS, including non-
ortho and mono-ortho congeners, in tree swallow eggs, nestlings, and adults at the
Kalamazoo River Area of Concern (KRAOC) and at an upstream reference site. There
was generally a 6-fold difference in tissue concentrations of total PCBS between the two
sites with concentrations at the KRAOC ranging from 0.42 to 32 pg PCB/g, wet weight.
Concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQSWHQAVjan) for
PCBs, based on bird-specific World Health Organization Toxic Equivalence Factors,
were 10 to 30-fold greater in the KRAOC than at the reference location. TEQSWHQAVian
ranged from 4.8 to 51 ng TEQ/g, wet weight at the KRAOC. Hazard quotients calculated
from literature-derived toxicity reference values were below 1.0 at both the target and
reference sites based on the no observed adverse effect level (NOAEL) and the lowest

observed adverse effect level (LOAEL).

Keywords: Birds, Bioaccumulation, Aquatic food chain, TEQS, PCBs

41

INTRODUCTION

PCBS were used in the production of carbonless copy paper and paper inks over
approximately 15 yrs (USEPA, 1976). Effluent containing polychlorinated biphenyls
(PCBs) was released into the Kalamazoo River during the recycling of carbonless copy
paper. As a result, a 123 km portion of the Kalamazoo River in southwest Michigan was
designated a Superfund site due to the presence of PCBS in fish, sediments, and
floodplain soils. PCBs have been linked to adverse effects in numerous mammalian
(Grant et al., 1974; Aulerich et al., 1977; Bursian et al., 2003) and avian species (Giesy et
al., 1994), especially reproductive effects. Recent studies have investigated mink
exposure (Millsap et al., 2004) and tree swallow reproduction (Neigh et al., 2004) at the
Kalamazoo River Area of Concern (KRAOC), but little information was available
regarding concentrations of PCBs in the tissues of passerine species. Two basic types of
methodologies were employed to assess trophic transfer and ecological risk to resident
avian species. The first methodology, the “bottom-up” or food web approach, predicted
dietary exposure, which was compared to threshold concentrations determined in
laboratory feeding studies (Fairbrother, 2003). The alternative approach, on which we
report here, measures concentrations of PCBs in the tissue of the receptor and compares

these to tissue-based toxicity reference values (TRVs).

Exposure to PCBs for all tissues was based on congener-specific analysis of 100

congeners and was reported as 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD) equivalents

(TEQSWHO-Avian) and total PCBS in order to assess risk to tree swallow populations on the

42

KRAOC, and to evaluate the consistency of the two methodologies for quantifying PCB
exposure. Both methods are assumed to evaluate the toxicity of PCB mixtures, but each
measure has its advantages and disadvantages. The TEQ method, adopted by the USEPA
(USEPA, 1989), describes the toxic action of non-ortho (coplanar) and mono-ortho
congeners, which are mediated through the aryl-hydrocarbon receptor (AhR) and additive
in toxicity. Effects mediated through this pathway are expected to be critical, and
therefore, overshadow the effects elicited through other pathways (Giesy and Kannan,
1998). Regulations based on this pathway are therefore considered protective of all toxic
responses. However, TEQS are species and endpoint-specific, so there are uncertainties
when extrapolating to wild species and other endpoints. A major weakness of the
concept is the disregard for pathways that do not act through the AhR pathway but may
contribute to the overall toxic response of the organism to the mixture (Giesy and
Kannan, 1989). The total PCB method of evaluating toxicity assumes the toxicities of all
congeners in the mixture are similar and additive, so all potential toxic contributions from
individual congeners are included in the assessment. The total PCB method does not
assess the toxicity of the different pathways and interactions between the pathways, so
the toxic response to the total PCB concentration can only be generalized and not

specifically described based on the mode of action.

The Kalamazoo River is located in southwest Michigan beginning at the confluence of
the north and south branches in Albion, Michigan, and flows northwest for approximately
200 km to Lake Michigan at Saugatuck, Michigan. The main stem of the Kalamazoo

River was dammed at ten locations, but three of the dams were partially dismantled in

43

1986, exposing approximately 205 ha of former PCB contaminated sediments, which are
now floodplain soils. Surveys of in-stream surface sediment (0-10 cm) indicate
concentrations range from less than 1.0 ng PCB/g, dry weight (dw) to 153 ug PCB/g, dw
with a mean concentration of ~ 3 pg PCB/g, dw (BBL, Inc., 1994a; Weston, Inc., 2002).
Surficial floodplain soils (0-25 cm) in the former impoundments range from less than 1.0
ng PCB/g, dw to 85 pg PCB/g, dw with mean values of ~ 11 ug PCB/g, dw (BBL, Inc.,

1994b; BBL, Inc., 1994c; BBL, Inc., 1994d).

The tree swallow (T achycineta bicolor) was selected as a surrogate species to determine
site-specific bioavailability and trophic transfer from sediments contaminated with PCBs
to upper trophic level avian receptors. This study focused on tree swallows as model
receptors of PCB accumulation in avian wildlife because of the presence of a previously
established nest box population at the baseline location and an abundance of tree
swallows residing throughout the river basin. The tree swallow diet consists largely of
emergent aquatic insects (Quinney and Ankney, 1985; Cohen and Dymerski, 1986;
McCarty, 1997), which are in contact with sediment during large portions of their life
cycle. The aquatic insects comprise an indirect exposure pathway of PCB contamination
from the sediment to tree swallows, and therefore, tree swallows are suitable monitors of
sediment contamination. Prior to egg laying, tree swallows spend two or more weeks
constructing nests (Kuerzi, 1941), and thus, concentrations of PCBs in eggs, passed by
maternal exposure, are related to local sources of contamination. A large database of
similar studies on tree swallow exposure to PCBs and productivity exist, which suggests

tree swallows are both tolerant of PCB contamination (McCarty and Secord, 1999) and

44

are adequate monitors of aquatic sources of PCBs (Ankley et al., 1993; Jones et al., 1993;

Bishop et al., 1999).

This study evaluated the risk of exposure to PCBS in tree swallows through the aquatic
food chain at a portion of the Kalamazoo River known to be contaminated with PCBS and
at an upstream baseline site unaffected by point sources and having background
concentrations of PCB in sediments. Previous reports based on this study elucidate no
statistical difference in productivity, fledging success, hatching success, brood size, and
the number of fledglings between the reference and KRAOC locations, but clutch size
was significantly greater at the reference location (Neigh et al., 2004). Based on these
data, overall reproductive health did not appear to be impaired at ecologically relevant
levels. Here, we present an alternate “top-down” approach in which site-specific
concentrations of PCBS (total PCBs and 2,3,7,8-tetrachloridbenzo-dioxin equivalents
(TEQSWHQAVian) in tree swallow adults, nestlings, and eggs are compared to literature-

derived threshold values to estimate risk in aquatic food web based passerine birds.

MATERIALS AND METHODS

Site details

Two locations were selected to evaluate exposure to PCBs in tree swallows. In 2000,
nest boxes were established within the KRAOC and additional boxes were added to an
already existing nest box trail at the reference location. Nest boxes were within the 100-

year floodplain and not more than 200 m from the river. The Fort Custer (FC) reference

45

site was located upstream of known sources of PCB contamination between the villages
of Augusta and Galesburg in southwest Michigan (Figure 2.1). The target study area was
located entirely within the KRAOC and 67 km downstream of the reference location.
The target area, the former Trowbridge Impoundment (TB), was formed in 1986 when
the superstructure of the dam was removed, which exposed the impoundment’s former
lake bottom. The former Trowbridge Impoundment stretches 7 km and encompasses 132
ha of exposed former sediments, now vegetated, and 70 ha of remaining impounded
water. As one of three similar impoundment areas, the TB study areas was selected as
the worst case scenario for wildlife exposure because it has the greatest surface area, total
PCB mass, and mean surficial concentration of PCBs in soils (~11 ug/g, dw) of any of

the Kalamazoo River impoundment areas (BBL, Inc., 1994c).

46

 
 

 

 

 

 

Z

<

53 ALLEGAN COUNTY ,

m z ; 117:

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2 MENT (KRAOC)

[d

a

3 FORT CUSTER STATE

RECREATION AREA

0 5 10 Miles CALHOUN COUNTY
E222:

 

 

 

N
T KALAMAZOO CqUNTY
Figure 2.1. Kalamazoo River Area of Concern (KRAOC) and reference site.

Tissue sampling

Eggs, nestlings, and adults were collected during spring and summer of 2001 and 2002.
No more than one fresh egg or one live nestling was taken from any box in a given year,
and the type of sample was randomly predetermined for each box upon nest initiation.
Dead adults, nestlings, and abandoned or addled eggs found in the nest boxes were
salvaged, assessed for cause of death, and PCB concentrations determined. Fresh eggs
were preferentially sampled 10 or more days after laying. Eggs were placed in a pre-

cleaned Pelican Case® (Torrance, CA, USA) for transport back to the field lab where

they were placed in solvent-rinsed jars and stored at 4°C. Individual nestlings were

47

selected randomly from predetermined broods on the day of sampling. Sampling of
nestlings occurred about one week prior to the expected fledge date to allow for
maximum growth while minimizing the chance that nestlings would fledge when
disturbed. Nestlings were quickly removed from nest boxes, transported out of audible
and visual range of the nest, and euthanized by cervical dislocation. Nestling tree
swallows are not sexually dichromatic, so the sex of individual nestling samples could
not be determined. Chicks were then placed in solvent rinsed jars and frozen at -20°C.
Adults were sampled at the end of the nestling period during 2002 and 2003. Adults
were captured by mist nets erected in close proximity to the nest boxes or by a trap door
mechanism. Adults were promptly euthanized by cervical dislocation, and sex, age,
weight, body length, tarsal length, and wing chord were determined. Sex was determined
based on the presence of a brood patch or cloacal protuberance. The carcasses were

placed in solvent rinsed sample jars and frozen at -20°C.

Chemical analysis

Eggs, nestlings, and adults were processed before chemical analysis. Eggshells were
removed, which left the contents Of the egg, including yolk and albumen, for sample
analysis. Wet weights of eggshells were measured and then dried in an oven at 80°C for
24 h to determine dry weight. Feathers, beaks, wings, legs, and stomach contents were
removed from adults and nestlings, and the whole body was homogenized in a solvent

rinsed grinder. Stomach contents were placed in cleaned vials and stored at -20°C.

48

Total concentrations of PCBS and DDT and its metabolites were determined by EPA
method 3540. All concentrations were reported as wet weight unless otherwise noted. A
known quantity of tissue was homogenized with anhydrous sodium sulfate (EM Science,
Gibbstown, NJ, USA) using a mortar and pestle. All samples, blanks, and matrix spikes
contained surrogate standards, PCB 204 (International Union of Pure and Applied
Chemistry) (AccuStandard, New Haven, CT, USA) and PCB 30 (AccuStandard, New
Haven, CT, USA). Extraction blanks using NaZSO4 were included with each set of
samples and Quality Assurance/Quality Control (QA/QC) sets composed of similar
tissues were included with each group of 20 samples. Samples were extracted with 400
ml of pesticide residue grade dichloromethanezhexane (3:1, v/v) for 18 h in a Soxhlet
extraction apparatus (VWR Scientific, Plainfield, NJ, USA). Extracts were concentrated
by rotary evaporation to a final volume of 11 ml. One ml Of the hexane extract was used
for lipid content determination. If deemed necessary, acid hydrolysis was performed.
Briefly, 10 ml of concentrated sulfuric acid was added to the extract and shaken for at
least 30 3. After separation of phases, the extract was transferred to another test tube, and
10 ml of water was added to remove acid residues from the extract. The remaining 10 ml
of extract was passed through a neutral/acidic silica gel column to remove non-target
analytes. Glass columns 30 cm in length and 15 mm in diameter were packed with
approximately 0.5 g anhydrous sodium sulfate and alternating layers Of 2 g 40% sulfiiric
acid (JT Baker, Phillipsburg, NJ, USA) impregnated silica gel and 2 g 100 to 200 mesh
size silica gel (Aldrich, Milwaukee, WI, USA). The extract was then evaporated to a

final volume of 1.0 ml under a stream of nitrogen. An aliquot of 0.5 ml was retained for

49

total PCB and DDT analytes, while non-ortho-substituted (coplanar) PCB congeners

were separated from the remaining aliquot, as described below.

PCBs including di- and mono-ortho-substituted congeners were quantified by use of a
gas chromatograph (Perkin Elmer AutoSystem and Hewlett Packard 5890 series 11)
equipped with a 63Ni electron capture detector (GC-ECD). A fused silica capillary
column (Zebron ZB-S; 5% phenylpolysiloxane, 30m x 0.25 mm inner diameter) with a
film thickness of 0.25 pm was used (Phenomenex, Torrance, CA, USA). The column
oven temperature was programmed to change from 120°C (1 min hold) to 160°C at a rate
of 10°C/min (1 min hold) and then to 250°C at a rate Of 2°C/min with a final holding
time of 10 min. Injector and detector temperatures were kept at 225°C and 375°C,
respectively. Helium and nitrogen were used as carrier and make up gas, respectively.
The standard contained 100 individual PCB congeners of known composition and
content. Congeners were identified by comparing sample peak retention times to those Of
the known standard. In sample extracts, concentrations of each congener were
determined by comparing the peak area to that of the appropriate peak in the standard
mixture. The method detection limit (MDL) was estimated to be 1 x 10'3 pg PCB/g.
TurboChrom (Perkin Elmer, Wellesley, MA, USA) or GC Chemstation software (Agilent
Technologies, Wilmington, DE, USA) was used to integrate the peaks. A spreadsheet
developed by the Michigan State University Aquatic Toxicology Laboratory was used to
quantify individual congeners. Total PCB concentrations were calculated as the sum of

all resolved PCB congeners.

50

Carbon column chromatography was used to separate non-ortho substituted PCB
congeners (IUPAC numbers 77, 81, 126, and 169) from co-eluting congeners and
interferences. Briefly, 30-cm glass columns, 15 mm in diameter, were packed with
anhydrous sodium sulfate, carbon dispersed on silica gel (Wako Chemicals, Richmond,
VA, USA), and anhydrous sodium sulfate. Twenty microliters of 50 pg/L radio-labeled
l3C coplanar PCB congeners (77, 81, 126 and 169) standard (Cambridge Isotope
Laboratories, Andover, MA, USA) in isooctane were added to each extract. The first
fraction, eluted with 100 ml 20% dichloromethane in hexane, was archived. The second
fraction, eluted with 200 ml of toluene, contained non-ortho coplanar PCB congeners.

The extract was then concentrated under a stream of nitrogen to a final volume of 20 pl.

Concentrations of non-ortho substituted PCBs and DDT metabolites were quantified by
gas chromatograph mass selective detector (GC-MS) (Hewlett Packard 5890 series 11 gas
chromatograph) equipped with a HP 5972 series detector. ‘ A fused silica capillary
column (as described above) was used. Coplanar PCB congeners and DDT analytes were
detected by selected ion monitoring at the two most abundant ions of the molecular
cluster. Detection limit varied with each sample, but the mean detection limit for all

samples was <100 pg PCB/g.

TE Q computation

Concentrations Of TEQSWHoAvian in bird tissues were calculated by multiplying the
concentration of individual PCB congeners by their respective bird-specific World Health

Organization (WHO) toxic equivalence factor (TEF) (van den Berg et al., 1998). Total

51

TEQ concentrations were calculated as the sum of detectable non-ortho and mono-ortho
PCB congeners (77, 81, 105, 118, 126, 156, 157, 167, and 169) and reported as wet
weight unless otherwise noted. Polychlorinated-dibenzo-dioxins and polychlorinated-
dibenzo-furans were not measured and were not included in TEQ computation. All data
were log-transformed for statistical analyses. These congeners are considered to have the
greatest relative potency to cause effects mediated through the AhR (Giesy and Kannan,
1998; Kannan et al., 2000). A sensitivity analysis was conducted in which congeners that
were not detected were assigned a proxy value equal to the detection limit or to zero
(Coady et al., 2004). The results of this analysis demonstrated that the calculated
concentrations of TEQWHQAVian did not differ substantially with either proxy value.
Therefore, a value of half the detection limit was assigned to congeners with
concentrations below the method detection limit. CO-eluting congeners were evaluated
separately. For example, congener 105 co-eluted with congener 132, PCB 156 frequently
co-eluted with congeners 171 and 202, and congener 157 frequently co-eluted with
congener 200. In order to report the most conservative TEQWHQAVian, the entire
concentration of the co-elution groups was assigned to the mono-ortho congener.
Overall, congeners 105, 156, and 157 contributed little to the total concentration of the

TEQWHQAVian in all samples from the Kalamazoo River, 3.7%, 1.8%, 0.4%, respectively.

Bioaccumulation calculation

Bioaccumulation factors (BAFs) were calculated by dividing the lipid normalized total

PCB or TEQWH0-Avian in the upper trophic level by the lipid normalized concentration in

52

the lower trophic level. BAFs were calculated using nestlings and adults sampled live

and eggs sampled fresh.

Statistical analyses

Statistical comparisons were made by use of SYSTAT (Evanston, IL, USA). Sample sets
were analyzed for normal distribution by Kolmogorov-Smirnovwone sample test with
Lilliefors transformation and for homogeneity of variance by F test. Samples were
generally log normally distributed, and therefore, all concentration data were log
transformed to obtain a normal distribution. Sample sets satisfying assumptions of
normality and homogeneity were compared by t-test, or in the case of multiple
comparisons, by a one-factor analysis of variance (ANOVA). All other data sets were
compared by Mann-Whitney U or Kruskal-Wallis non-parametric tests. The criterion for

significance used in all tests was p < 0.05.

Two eggs were sampled from three different nests. In two of the nests, eggs were addled,
and the concentration of each of the eggs was not more than one standard deviation
different from the mean of the population. The mean concentration of PCBs in the
populations were calculated based on the concentrations in eggs of all other nests and the
average concentration of eggs in the nests in which multiple eggs were sampled. In one
nest, one egg was sampled fresh and the other addled, so these values were evaluated
separately when considering differences between fresh and addled eggs, but they were

averaged to calculate the mean concentration of PCBs in the population.

53

Assessment of risk

Risk was assessed through hazard quotients (HQs) by comparing concentrations of PCB
measured in eggs to tissue-based toxicity reference values (TRVs) based on the no
observed adverse effect level (NOAEL) and the lowest observed adverse effect level
(LOAEL) for total PCBs and the NOAEL for TEQS (Table 2.1). Concentrations of PCBS
in eggs were considered the most sensitive metric for assessing effects induced by PCBs.
Therefore, the assessment of potential risks based on TRVs derived from the exposure of
eggs to PCBs was considered to be a conservative estimate of risk at all life stages (Giesy
et al., 1994). HQs were calculated as the tissue concentration divided by the tissue-based

TRV.

Table 2.1. Literature-derived tree swallow toxicity reference values (TRVs) used to
calculate hazard quotients based on the no Observed adverse effect level (NOAEL) and

the lowest Observed adverse effect level (LOAEL). Reference number is located next to A

 

 

each value.
Tissue Based Reference
TRV
Total PCBS (pg PCB/g)
NOAEL 26.7 USEPA, 2000
LOAEL 63.0 Custer et al., 2003
Total T EQ (ng/g, ww)
NOAEL 13 USEPA, 2000
LOAEL NA

 

54

RESULTS

Total PCB and organochlorine concentrations
Concentrations of PCBs in tree swallows were significantly different between sites.
Concentrations of PCBs in adult tree swallows ranged from 0.44 to 32 pg PCB/g at TB
and 1.0 and 2.0 pg PCB/g at FC. There was no statistically significant difference
between sexes of the adults at TB, and the sample size was too small at PC to evaluate
differences between sexes. There was no statistically significant difference in total PCB
concentrations between eggs taken fresh or addled eggs, so all sample types were
combined for statistical analyses. Likewise, there was no statistically significant
difference in concentrations of PCBs between nestlings taken alive or salvaged carcasses,
so they were also combined for analysis. In both eggs and nestlings, there was a 6-fold
difference between sites in concentrations of PCBs (Table 2.2). Concentrations of PCBs
in nestlings and eggs from TB were both significantly greater than those at F C (Student’s
t-test, p < 0.001). PCB concentrations of nestling tree swallows ranged from 0.95 to 7.5
pg PCB/g at TB to a significantly smaller concentration at FC ranging from 0.14 to 2.0
pg PCB/g. Egg concentrations ranged from 1.2 to 15 pg PCB/g at TB and 0.18 to 2.5 pg

PCB/g at FC.

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DDT and its metabolites were detected in all samples from both sites. p',p’- DDE
occurred at the greatest concentration of the measured analytes in all samples, which
contributed 98% of the sum of total DDT concentrations in all samples. The sum of all
measured metabolites was used to calculate total DDT concentrations. Concentrations of
total DDT at TB and F C were not significantly different (Mann-Whitney U, p = 0.465)
due to large variances in the data, but the means were 3-fold different between sites. The
mean (:1: 1 SD) concentration when all eggs were combined was 1.5 (1.2) pg DDT/g at
TB and 0.45 (0.13) pg DDT/g at FC. Mean (:1: 1 SD) concentrations in addled eggs were
2.3 (0.32) pg DDT/g at TB and 0.32 (0.072) pg DDT/g at FC, and concentrations in fresh

eggs were 0.95 (1.3) pg DDT/g at TB and 0.54 (0.030) pg DDT/g at FC.

T E QwHo- A.,-0,, concentrations

Mean concentrations of TEQSWHoAvim in eggs and nestlings at FC and TB were
significantly different (Student’s t-test, p < 0.001) (Table 2.3). Although sample sizes
were insufficient to evaluate differences between groups at FC, there were no statistically
significant differences between fresh and addled eggs or live and salvaged nestlings at
TB. Tree swallow eggs contained mean TEQ concentrations ranging from 0.21 to 2.4 ng
TEQ/g at TB and 0.021 to 0.100 ng TEQ/g at F C. Nestlings at TB also had the greatest
concentration (0.26 to 1.3 ng TEQ/ g) and another nestling at PC the lowest (2.6 x 10'3 to

0.047 ng TEQ/g).

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58

Statistical analysis could not be completed for the comparison of adult tissues between
sites due to small sample sizes at FC (n = 2), but at TB there was no difference between
sexes. All adult samples from both locations had detectable concentrations of non-ortho
PCBS. The average (:h 1 SD) TEQWHOAW in adult tissues at TB was 2.2 :1: 1.8 ng TEQ/g
and 0.22 :1: 0.030 ng TEQ/g at FC. An adult from TB had the greatest TEanOmm for

the study (4.8 ng TEQ/g).

Five of the 8 mono-ortho congeners were regularly detected in samples from both TB and
FC, but congeners 114, 123, and 189 were not detected in samples from either site.
Samples were excluded from the analysis of TEQqumian concentrations when at least
one non-ortho congener was not quantifiable due to interferences with co-eluting
congeners with the exception of PCB 169, which was not quantifiable in 65% of all
samples. Congener 169 represented <1% of the total TEQWHGMan concentrations in
those samples for which it was reported. At least one of the coplanar congeners 77, 81,
and 126 were not quantifiable due to co-eluting congeners or were not above the
detection limit in 71% of all samples at FC. Alternatively, only 11% of samples at TB
had at least one of the three regularly detected coplanar congeners with concentrations
that were not quantifiable or not detectable. For the remaining samples, the congeners
detected at levels greater than the detection limit and the frequency of detection at TB
were in the following rank order: PCB 77 = 105 = 118 (100%) > 157 (97%) > 81 = 156
(95%) > 126 (89%) > 167 (70%) > 169 (51%). Similarly, the rank order of the frequency

of detection for mono-ortho and non-ortho congeners at PC was as follows: PCB 118

59

(100%) > 105 (97%) > 77 = 167 (86%) > 156 = 157 (77%) > 126 (66%) > 81 (43%) >
169 (20%). Coplanar PCB congeners 81 and 126 have the greatest AhR-mediated
potency relative to other congeners and were detected in all TB nestling and adult
samples and in 89% of egg samples at TB. Together they comprised 8.3% $6.3 (mean 3:
1 SD) of the total concentration of TEanOmm in tissues at TB and 32.2% i 25.6 of the
total TEQWHQAVjan at PC (Figure 2.2). Congener 77 occurred at the greatest
concentration in all matrices and contributed the greatest proportion to the total TEQWHO.
Avian, 89.4% at TB and 67.8% at FC. Congener 167 was not reported in 22% of samples
due to interference with co-eluting congeners, but in the samples without interferences,

congener 167 represented <1% of the total TEQWH0-Avian.

100% '
90% '
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60% ' I126
50% ' I81
40% P
30% . D77
20% '
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Percent of total TEQ

 

 

 

 

 

 

Figure 2.2. Contribution of selected congeners to total TEQ in egg, nestling, and adult

samples from the Fort Custer reference site and the Trowbridge Impoundment.

60

Bioaccumulation
BAFs calculated from total PCBS and TEQS were less than 1.0 between egg and nestling
and adult and egg but were greater than 1.0 between nestling and adult, except in 2001

when the egg to nestling BAF was greater than 1.0 at TB (Table 2.4).

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Accumulation rates were calculated as the difference in total mass of PCBs and TEQS
between nestlings and eggs in a nest divided by the days of life (Custer and Custer,
1995). Both a nestling and an egg were sampled from 5 nests, which allowed for the
calculation of accumulation rates in those nests. Accumulation rates of 4.4 and 7.7 ug
PCB/d were calculated for nests at TB during 2001 and 2002, respectively, and 0.90 to
1.1 ug PCB/d at FC for 2001 and 0.053 pg PCB/d at F C for 2002. Accumulation rates of
TEangAvim were 0.79 and 1.2 ng TEQ/d at TB in 2001 and 2002, respectively, while

accumulation rates of TEQS at PC in 2001 were 0.014 to 0.082 ng TEQ/d in 2002.

The relative contributions of non-ortho and mono-ortho congeners were evaluated by
standardizing the TEQ to the total PCB concentration for each trophic level and

comparing this relative potency between trophic levels via a potency ratio (Equation 1).

Equation 1: (Concentration of TEQS/Concentrations of Total PCBSMMMC level 2

(Concentration of TEQS/Concentrations of Total PCBs)m,,hic level 1

The potency ratio was calculated via methods outlined by Froese et a1. (1998) to describe
changes in toxicity between trophic levels. Mean relative potencies (concentration of
TEQS/concentration of total PCBs) used to calculate potency ratios are reported (Table
2.2). The egg to nestling potency ratio at TB and FC were 1.4 and 0.62, respectively.
The ratios from nestling to adult and adult to egg were 1.3 and 0.52 at TB and 2.6 and

0.60 at FC, respectively.

63

Assessment of risk

Based on the NOAEL for both total PCBs and TEQSwquvian (mean and 95% CI), all
HQs for egg, nestling, and adult tissue concentrations were all less than 0.3 at F C. HQs
based on the mean and 95% UCL for eggs, nestlings, and adults at TB were also less than
1.0 for the NOAEL and LOAEL of total PCBs and the NOAEL for TEQS (Figure 2.3).
No samples from this study exceeded the LOAEL threshold, and only one adult sample
from TB exceeded the NOAEL for total PCBs, yielding 3 HQ of 1.2. These results

suggest that the tree swallow population was not at risk for effects induced by PCB

exposure.

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65

DISCUSSION

Total PCB and DDT concentrations

Concentrations of PCBS in tree swallow eggs, nestlings, and adults at the FC reference
site were significantly less than those at the TB site. Reference sites on the Thompson
River, Fraser River, Fox River, and around the Great Lakes had PCB contaminant levels
in tree swallow tissues within a 2-fold range of those found at PC with no corresponding
reproductive effects (Custer et al., 1998; Bishop et al., 1999; Secord et al., 1999; Harris

and Elliott, 2000).

Concentrations of PCBs found in tree swallows from the KRAOC were generally less
than at other sites in the Midwest and New York where PCBs have been identified as a
chemical class of concern (Jones et al., 1993; Bishop et al., 1999; Secord et al., 1999).
Mean concentrations of PCBs in eggs and nestlings from the KRAOC were 5.1 pg PCB/g
and 3.1 pg PCB/g, respectively. Tissues from tree swallows at the Fox River near Green
Bay were most similar to those at the KRAOC with mean concentrations of PCBS in eggs
and nestlings as great as 4.1 pg PCB/g and 3.0 pg PCB/g, respectively (Custer et al.,
1998). Approximately 200 km from the KRAOC, tree swallows from Saginaw Bay, MI,
contained slightly lesser tissue concentrations of 0.60 to 1.4 pg PCB/g in eggs and 0.17 to
1.0 pg PCB/g in nestlings (Nichols et al., 1995). An egg concentration lO-fold greater
than the greatest egg concentration at the KRAOC and a nestling concentration 8—fold
greater than the greatest concentration at our site were reported in tree swallows from the

Great Lakes (Bishop et al., 1999). To date, the greatest concentration of PCBS reported

66

in eggs or pipping chicks were at the Housatonic River, MA (101 pg PCB/g) (Custer et
al., 2003), and the greatest concentration in nestlings were reported at the Hudson River
(62.2 pg PCB/g) (Secord et al., 1999). Concentrations of PCBS at both sites were 20-fold
greater than at the KRAOC. In addition to concentrations of PCBS in eggs and nestlings,
few studies besides the current study have reported tissue concentrations in adults based
on more than a few incidentally salvaged samples. In a single adult female, a PCB
concentration of 114 pg PCB/g was reported at one Hudson River site (Secord et al.,
1999). That concentration was considerably more than for adults at TB (mean = 8.7 pg

PCB/g).

Sources of DDT and its metabolites at the KRAOC are unknown, but are likely related to
former agricultural practices and the prevalence of orchards in downstream portions of
the Kalamazoo River drainage system. Although DDT concentrations were greater at the
TB site than at the FC reference site, they were not sufficient to affect the viability or
hatching success of tree swallow eggs. Hatching and overall productivity were
comparable between the two sites, and no unusual instances of shell breakage were noted
at either of the Kalamazoo River populations studied (Neigh et al., 2004). A
concentration of 2.0 pg DDE/g in eggs has been suggested as a threshold for effects in
raptor species, which was similar to the mean for the TB population (Elliot and Harris,
2002). Concentrations of DDE in the abandoned eggs of tree swallows near Denver, CO,
were 2.8 pg DDE/g, while concentrations of DDE in attended eggs were 1.3 pg DDE/g
(DeWesse et al., 1985). Although concentrations of DDE may be near a threshold for

effects, the lack of reproductive effects normally attributed to DDE exposure and the

67

absence of a species specific threshold suggests that DDE did not have a significant

impact on tree swallow reproduction at the Kalamazoo River.

TE Q tissue concentrations

If concentrations of TEQS and those of total PCBS were correlated it would be expected
that there were few AhR-active compounds contributing to the total TEQ concentration
(Jones et al., 1993). Although, they were calculated with different TEQS, the calculated
TEQSWHQ-AVian for tree swallows at the KRAOC were similar to those TEQS calculated
for other PCB contaminated sites in the Midwestern United States (Ankley et al., 1993;
Jones et al., 1993; Froese et al., 1998). Concentrations of TEQSwnamm in eggs,
nestlings, and adults from the KRAOC were 10 to 30-fold greater than concentrations at
the reference site, compared to a 3 and 10-fold difference in concentrations of TEstno-
Avian between reference sites and contaminated sites at the Thompson and Fraser Rivers,
respectively (Harris and Elliott, 2000). Concentrations of TEstnoAvm in nestling tree
swallows at the FC reference site were at least 4-fold greater than the upstream reference
sites on the Thompson and Fraser Rivers and were most similar to the downstream site of

the Thompson River (Harris and Elliott, 2000).

Besides the statistically significant difference in total TEstnoAviafl between sites, there
was also a difference in the proportion that each congener contributed to the overall
TEQWHaAvim. As has been observed at other sites (Secord et al., 1999; Custer et al.,
2002), congeners 77 and 126 contributed the greatest relative proportion of the total

TEQWHGAvian concentrations at both PC and TB. However, the contribution of PCB

68

congener 77 was significantly greater at TB in all life stages than at PC (Student’s t-test,
p < 0.001). In contrast, PCB congeners 81 and 126 contributed a significantly greater
proportion to the total TEQSWHOAVm at PC when evaluated together or as individual
components than at TB (Student’s t-test or Kruskal-Wallis, p < 0.05). The prevalence of
PCB congener 77 at TB was likely due to the presence of this congener in the original
Aroclor mixture, while the proportion of PCB congeners 81 and 126 comprising the
TEQSwquvim at F C could be attributed to the greater TEFSWHO-Avian of these congeners.
Other mono-ortho congeners also contributed a greater proportion of the total TEano.
Avian at PC than at TB, but the overwhelming presence of PCB congener 77 at TB likely

contributes to this observation.

Bioaccumulation

Tissue concentrations were normalized to lipid content and compared between trophic
levels. Bioaccumulation of PCBs observed in this study was similar to that observed in
other studies (Ankley et al., 1993; Custer et al., 1998; Froese et al., 1998; Custer et al.,
2002). The BAF from egg to nestling was less than from nestling to adult. This is due to
growth dilution of the chicks and fugacity effects in the adults (Jones et al., 1993). The
egg to nestling BAFs would be expected to exceed 1.0 if nestlings are exposed to
concentrations of PCBS in the diet that are greater than would be necessary to offset
growth dilution. The BAF of 1.5 observed in tree swallow nestlings from TB suggests a
dietary exposure. The contribution of site-wide contamination during the nestling stage
can be assessed because the sedentary behavior of altricial tree swallow nestlings, and the

relatively small feeding range of the adults ensures that dietary exposure and subsequent

69

accumulation in chicks results from on-site dietary exposure. Therefore, the egg to
nestling BAF is very informative when evaluating the bioaccumaltive potential of a
toxicant at a specific site. Overall, the Kalamazoo River BAFs were slightly less than
those found at the Fox River (6.18 and 3.47) (Custer et al., 1998), but were comparable to

those on the Hudson River (2.0 and 4.0) (Secord et al., 1999).

In nestlings, the rate of accumulation of PCBs can also be evaluated based on daily
accumulation rates, which account for the age of nestlings and the concentration
contributed by the egg (Custer and Custer, 1995). The calculation of daily accumulation
rates is useful in elucidating whether nestlings were exposed to concentrations of PCBS
from the diet. Accumulation rates at TB (4.4 and 7.7 pg PCB/d) were similar to those
reported for contaminated sites at the Fox River (1.34 to 6.69 pg PCB/d) (Custer et al.,
1998), but were less than those measured at the Housatonic River (34 to 76 pg/d) (Custer
et al., 2003). Accumulation rates at PC (0.053 to 1.1 pg/d) were similar to the reference
site at the Housatonic River (-0.30 to 1.0 pg/d) (Custer et al., 2003) and contaminated
sites at the Wisconsin River (0.40 to 0.70 pg PCB/d) (Custer et al., 2002). The
accumulation rate in KRAOC tree swallows is less than in piscivorous birds, such as the
Forster’s tern (Sterna forsteri), which had accumulation rates of 15 pg PCB/d (Ankley et

al., 1993).

The greatest increase in bioaccumulation was between nestlings and adults. FC
accumulation factors were generally greater than at TB, which likely resulted from the

low concentrations of PCBs at the site, especially in nestlings. Concentrations near the

70

detection limit may be difficult to quantify due to baseline noise, and so, the difference in
concentrations of PCBs in the nestling and adult tissue is great. When evaluating the
nestling to adult BAF, the contribution of off-site exposure and also maternal deposition
in the lipids of eggs needs to be considered. At the KRAOC, most female birds were
captured post-reproduction, and no difference in the concentration of male and female
tree swallows was observed. Perhaps dietary contributions to the body burdens of adults
had already accumulated to pre-reproductive levels when sampling was conducted, or the
loss of body burden to maternal deposition was not significant in our population.
Therefore, concentrations of PCBS in adults were greater than in nestlings due to on-site

and off-site exposure, as well as, the lack of growth dilution.

Potency ratios were generally greater than 1.0 for both the egg to nestling and nestling to
adult, which suggests that the contribution of non-ortho and mono-ortho congeners to the
overall toxicity increased at higher trophic levels. A ratio of 1.0 between egg and adult
was expected because there is little metabolism or grth dilution in the egg, and the egg
burdens are inherited from the adult. However, at the KRAOC, potency ratios were 0.60
and 0.52. This suggests that congeners contributing the greatest concentrations to the
relative toxicity did not pass into the egg. Bioaccumulating congeners in the penta-,
hexa-, and hepta- homologue groups contribute the greatest amount to the total PCB
concentration in adult tree swallows, while less-chlorinated congeners in the tri- and
tetra-homologue groups contribute a lesser amount (Figure 2.4). The accumulation of
these congeners likely led to the greater relative potency and overall toxicity of the

congener mixture found in adults. A greater proportion of total PCBS in eggs and

71

nestlings were contributed by the tri- and tetra-homologue groups, and a lesser proportion
were contributed by the more chlorinated homologue groups. The greater concentration
of the bioaccumulating congeners in the adults and the greater potency ratio in the adults
suggests that the toxicity of PCBS in the KRAOC increases withtrophic level, but that the
adults contribute a metabolized, relatively less-toxic mixture to the eggs. Overall, adults
appear to contain greater proportions of bioaccumulating congeners, and the mixture of
congeners in adults is more toxic than in lower trophic levels. The proportionate
contribution of congeners in eggs and nestlings is similar, but the toxicity of the mixture

increases with trophic level.

72

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73

Assessment of risk

Toxicity reference values (TRVs) used to calculate hazard quotients were chosen for this
study based on several criteria, which included: 1) the use of wildlife species over
traditional laboratory species whenever possible; 2) chronic exposure including sensitive
life stages; 3) the evaluation of ecologically relevant endpoints; 4) minimal co-
contamination; 5) multi-year studies; 6) and total PCB or TEQ values were reported or
could be calculated. TRVs were derived from several studies for various tissue matrices
(Table 2.1). Hudson River studies were included because they used the same species as
in this study, and are the only studies known to observe reproductive effects in tree
swallows attributable to exposure to PCBS (USEPA, 2000). Co-contaminants are also
believed to be less than the threshold concentrations for effects. There were no
laboratory studies using tree swallows, and therefore, this field study was deemed the
most appropriate estimate of TRV values. Reproductive effects including decreased
hatching, increased abandonment, lower quality nests, and abnormal plumage coloration
were reported in tree swallows at PCB contaminated sites relative to an uncontaminated
area. In order to be protective of wildlife species, the Hudson River location with the
lowest site-wide mean concentration of PCBs in eggs was chosen as the no observed
adverse effect level (NOAEL). A NOAEL value of 26.7 pg PCB/g, w for eggs,
nestlings, and adults was used. The TEanOmm reported for eggs in this study was also
used as the most conservative TEanGmm estimate of the NOAEL (13 ng TEQ/g). The
lowest observed adverse effect level (LOAEL) for total PCBs was derived from a
Housatonic River study in which hatching success was impaired during two years of the

study (Custer et al., 2003). The least concentration of total PCBs in pipping chicks from

74

the two years (63 pg PCB/g) was used as the LOAEL. This study was deemed
appropriate because effects were observed in two consecutive years and sensitive
reproductive endpoints were evaluated. A LOAEL based on TEQSWHOAWan could not be

derived from the literature.

Hazard quotients of less than 1.0 suggest that tissue concentrations in all stages of the tree
swallow life cycle were less than the threshold for effects based on the LOAEL. In most
instances, even based on the more conservative NOAEL, HQ were less than 1.0 for all
tissues (Figure 2.3). It should be noted that the true effect level for individuals rests
somewhere between the NOAEL and LOAEL, and that even conservatively, population
effects are not expected at a HQ of 10.0. Thus, while a few individuals did have NOAEL
HQ values between 1.0 and 2.5, reproductive dysfunctions would not be expected nor
were any seen (Neigh et al., 2004). Tree swallows on the Hudson River had
concentrations of PCBS that were lO-fold greater than the concentrations observed at the
KRAOC and reproductive effects were barely identifiable above the variation naturally

inherent in field studies (Secord et al., 1999).

Multiple lines of evidence including both exposure and effects were explored to quantify
risk to passerine species with an aquatic-based diet. Both the total PCB and TEQ method
of evaluating exposure concentrations resulted in similar conclusions of little to no risk to
tree swallows species at the KRAOC. Even when the most conservative TRV criteria
were utilized, tissue concentrations at the site suggest that only those individuals with the
greatest exposure may be at risk for effects attributable to PCBS, but for the population as

a whole, the current concentrations of PCBs are less than the threshold for effects

75

Accordingly, other studies with similar tissue concentrations did not observe reproductive
effects attributable to on-site exposure to PCBS. In short, multiple lines of evidence
based on three years of observation find that KRAOC tree swallow populations are not

affected by PCB contamination at an ecologically relevant level (Neigh et al., 2004).

CONCLUSION

Prior to this study little information was available on the extent of PCB exposure and
potentially related effects on Kalamazoo River passerine birds. Passerines are not only
important ecological receptors in their own right, but they are a potential prey component
of higher food web receptors within the Kalamazoo River basin, including the great
horned owl (Bubo virginianus) and bald eagle (Haliaeetus Ieucocephalus). Elevated
concentrations of PCBs in TB passerine nestlings indicate environmentally available
concentrations of PCBS in the vicinity of the TB nests. PCB concentrations contained in
adults and eggs indicate the presence of life cycle body burdens, which are critical for
evaluation of the health and sustainability of passerine populations. Here, we utilized
site-specific data to perform a risk-based evaluation of passerine health and sustainability
in PCB contaminated areas of the Kalamazoo River. The evaluation directly compared
exposure and productivity data for the target area to that of the FC reference area of the
Kalamazoo River. Concentrations of PCBs were significantly greater in tree swallows
from the KRAOC than those from the upstream reference site, and they were comparable
to other PCB-contaminated sites in the region. Based on a three year site specific

multiple lines of evidence approach, tree swallows from the KRAOC region of the

76

Kalamazoo River were exposed to PCBS at concentrations that were significantly greater
than similar areas without point source inputs. However, these exposures were less than
those expected to cause population level effects, and no effects were observed in

Kalamazoo River tree swallow populations.

77

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JP, Jones PD, Hagley C. 1993. Uptake of planar polychlorinated biphenyls and
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Aulerich RJ, Ringer RK. 1977. Current status of PCB toxicity to mink, and effect on their
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BBL, Inc. 1994b. Allied Paper, Inc/Portage Creek Kalamazoo River Superfund Site
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phase I TBSA soil sampling. Blasland, Bouck, & Lee, Incorporated. Syracuse,
NY, USA.

BBL, Inc. 1994c. Allied Paper, Inc/Portage Creek Kalamazoo River Superfund Site
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Incorporated. Syracuse, NY, USA.

BBL, Inc. 1994d. Allied Paper, Inc/Portage Creek Kalamazoo River Superfund Site
Remedial Investigation/Feasibility Study. Draft technical memorandum 12,
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Blasland, Bouck, & Lee. Syracuse, NY, USA.

Bishop CA, Mahony NA, Trudeau S, Pettit KE. 1999. Reproductive success and
biochemical effects in tree swallows (T achycineta bicolor) exposed to chlorinated
hydrocarbon contaminants in wetlands of the Great Lakes and St. Lawrence River
Basin, USA and Canada. Environ Toxicol Chem 18:263-271.

Bursian SJ, Aulerich RJ, Yamini B, Tillitt DE. 2003. Dietary exposure of mink to fish
from the Housatonic River: Effects on reproduction and survival. Final Report.
Weston Solutions, West Chester, PA, USA.

Coady KK, Blankenship AL, Neigh AM, Kay, DP, Zwiemik MJ, Strause K, Park CS,
Bradley PW, Newsted JL, Jones PD, Giesy JP. 2004. Differential accumulation of
PCB congeners in the aquatic food web at the Kalamazoo River Superfund Site,
Michigan, USA. Environ Sci Technol Submitted.

78

Cohen R, Dymerski ML. 1986. Swallows taking insects from pond surfaces. Wilson
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Custer TW, Custer CM. 1995. Transfer and accumulation of organochlorines from black-
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Custer CM, Custer TW, Allen PD, Stromberg KL, Melancon MJ. 1998. Reproduction
and environmental contamination in tree swallows nesting in the Fox River
Drainage and Green Bay, Wisconsin, USA. Environ T oxicol Chem 17: 1786-1798.

Custer TW, Custer CM, Hines RK. 2002. Dioxins and congener-specific polychlorinated
biphenyls in three avian species from the Wisconsin River, Wisconsin. Environ
Pollut 119:323-332.

Custer CM, Custer TW, Dummer PM, Munney KL. 2003. Exposure and effects of
chemical contaminants on tree swallows nesting along the Housatonic River,
Berkshire County, Massachusetts, USA, 1998-2000. Environ Toxicol Chem
22:1605-1621.

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measurements for tree swallows T achycineta bicolor in Colorado. Bull Environ
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Elliot J E, Harris ML. 2002. An ecotoxicological assessment of chlorinated hydrocarbon
effects on bald eagle populations. Reviews in Toxicology 4: 1-60. Fairbrother A.

2003. Lines of evidence in wildlife risk assessments. Human and Ecological Risk
Assessment 9: 1475-1491.

Froese KL, Verbrugge DA, Ankley GT, Niemi GJ, Larsen CP, Giesy JP. 1998.
Bioaccumulation of polychlorinated biphenyls from sediments to aquatic insects

and tree swallow eggs and nestlings in Saginaw Bay, Michigan, USA. Environ
T oxicol Chem 172484-492.

Giesy JP, Ludwig JP, Tillitt DE. 1994. Deformities in birds of the Great Lakes Region:
Assigning causality. Environ Sci Technol 28:128A-l 35A.

Giesy JP, Kannan K. 1998. Dioxin-like and non-dioxin-like toxic effects of
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28:511-569.

Grant DL, Moodie CA, Phillips WEJ. 1974. Toxicodynamics of Aroclor 1251 in the male
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Harris ML, Elliott J E. 2000. Reproductive success and chlorinated hydrocarbon
contamination in tree swallows (T achycineta Bicolor) nesting along rivers
receiving pulp and paper mill effluent discharges. Environ Pollut 110:307-320.

Jones PD, Giesy JP, Newsted JL, Verbrugge DA, Beaver DL, Ankley GT, Tillitt DE,
Lodge KB, Niemi GJ. 1993. 2,3,7,8-Tetrachlorodibenzo-p-dioxin equivalents in

tissues of birds at Green Bay, Wisconsin, USA. Arch Environ Contam Toxicol
24:345-354.

Kannan K, Blankenship AL, Jones PD, Giesy JP. 2000. Toxicity reference values for the
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Kuerzi RG. 1941. Life history studies of the tree swallow. Proceedings of the Linnaean
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McCarty JP. 1997. Aquatic community characteristics influence the foraging patterns of
tree swallows. Condor 99:210-213.

McCarty JP, Secord AL. 1999. Reproductive ecology of tree swallows (Tachycineta

bicolor) with high levels of polychlorinated biphenyl contamination. Environ
Toxicol Chem 18:1433-1439.

Millsap SD, Blankenship AL, Bradley PW, Jones PD, Kay DP, Park CS, Zwiemik MJ,
Giesy JP. 2004. Comparison of risk assessment methodologies for exposure of
mink to PCBS on the Kalamazoo River, Michigan, USA. Environ T oxico] Chem
In press.

Neigh AM, Zwiemik MJ, MacCarroll MA, Newsted JL, Blankenship AL, Jones PD, Kay
DP, Giesy JP. 2004. Productivity of tree swallows (T achycineta bicolor) exposed
to PCBs at the Kalamazoo River Superfund Site. J Toxicol Environ Health Part A
Submitted.

Nichols JW, Larsen CP, McDonald M, Niemi GJ, Ankley GT. 1995. A bioenergetics-
based model for accumulation of polychlorinated biphenyls by nesting tree
swallows, T achycineta bicolor. Environ Sci T echnol 29:604-612.

Quinney TE, Ankney CD. 1985. Prey size selection by tree swallows. Auk 102:245-250.
Secord AL, McCarty JP, Echols KR, Meadows JC, Gale RW, Tillitt DE. 1999.
Polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents in tree

swallows from the Upper Hudson River, New York State, USA. Environ T oxicol
Chem 18:2519-2525.

USEPA. 1976. PCBs in the United States industrial use and environmental distribution:

Task 1. EPA 560/6—76—005. United States Environmental Protection Agency,
Washington, DC, USA.

80

USEPA. 1989. Interim procedures for estimating risk associated with exposures to
mixtures of chlorinated dibenzo-p-dioxins and dibenzofurans (CDDs and CDFs)
and 1989 update. EPA/625/3-89/016. United States Environmental Protection
Agency, Washington, DC, USA.

USEPA. 2000. Revised Baseline Ecological Risk Assessment. Hudson River PCBS
Reassessment. Phase 2 Report. US. Environmental Protection Agency,
Washington, DC, USA.

van den Berg M, Bimbaum L, Bosveld ATC, Brunstrom B, Cook P, Feeley M, Giesy JP,
Hanberg A, Hasegawa R, Kennedy SW, Kubiak T, Larsen JC, van Leeuwen FXR,
Liem AKD, Nolt C, Peterson RE, Poellinger L, Safe S, Schrenk D, Tillitt D,
Tysklind M, Younes M, Waem F, Zacharewski T. 1998. Toxic equivalency
factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environ
Health Perspect 106:775-792.

Weston, Inc. 2002. Removal assessment report for Allied Paper- Kalamazoo River site
Otsego/Plainwell, Michigan. TDD 0103-002. US. Environmental Protection
Agency, Washington, DC, USA.

8|

Chapter 3
Reproductive success of passerines exposed to PCBS through the terrestrial food web of

the Kalamazoo River

Arianne M. Neigh T, Matthew J. Zwiemik TI, Patrick W. Bradley T, Denise P. Kay *, Paul
D. Jones 71, Carrie A. Ruppert 1, Alan L. Blankenship *1, John L. Newsted 1, John P.

Giesy T15

TZoology Department, Center for Integrative Toxicology, National Food Safety and

Toxicology Center, Michigan State University, E. Lansing, MI 48824

*ENTRIX, Inc., Okemos, MI 48864

§Biology and Chemistry Department, City University of Hong Kong, Kowloon, Hong

Kong, SAR, China.

82

ABSTRACT

The eastern bluebird (Sialia sialis) and the house wren (T roglodytes aedon) were
identified as ecological receptors for the identification of exposure and potential effects
stemming from polychlorinated biphenyl (PCB) contamination in floodplain soils of the
Kalamazoo River Superfund Site, Kalamazoo, MI. Concentrations of PCBs in tissues
and diets of these two bird species were statistically greater in areas downstream of the
point sources than at an upstream reference location. Here we report concurrent
evaluations of hatching success, fledging success, productivity, clutch size, brood size,
egg size, and growth. Productivity of eastern bluebirds (Sialia sialis) was significantly
less at the downstream location as compared to background during this three-year study.
Hathcing success, clutch size, and predicted brood size were significantly less in early
clutches of house wrens (Troglodytes aedon) at the contaminated location relative to the
upstream reference location, but fledging success was greater at the contaminated
location over the entire study period. Growth was significantly different during one of
the three years for each species at the contaminated location compared to the reference
location, but growth was similar when the entire study period was evaluated. The
presence of below threshold concentrations in the tissues and diets of the passerine birds
suggest that other factors besides PCB exposure such as habitat, small sample size, and

co-contaminants may be affecting reproduction.

Keywords: Polychlorinated biphenyls, Productivity, Birds, Eastern bluebird, House

Wren, Eggs, Hatching success

83

INTRODUCTION

The Kalamazoo River was designated a Superfund site in 1990 due to the presence of
paper waste contaminated with polychlorinated biphenyls (PCBS) released during the
carbonless copy paper recycling process (MDEQ, 2003). The Kalamazoo River Area of
Concern (KRAOC) supports a diverse terrestrial ecosystem along its course, including
205 ha of formerly impounded contaminated sediment exposed when three dams were
partially dismantled to their sill level. While the effects of PCB contamination on various
species with aquatic-based diets is well documented (Giesy et al., 1994; Kubiak et al.,
1989; Ludwig et al., 1993; Millsap et al., 2004; Yamashita et al., 1993), few studies have
evaluated PCB contamination in wildlife exposed through terrestrial food webs
associated with riverine ecosystems. The presence of PCBs in soil and sediment at the
site requires identification of effects in terrestrial and aquatic endpoints during the risk
assessment process. This study focused on the effects of PCB contamination in two
passerine birds with predominantly terrestrial diets, while risk to passerines dependent on

the aquatic food web is presented elsewhere (Neigh et al., 2004a).

The tree swallow has a well-established history as a passerine contaminant monitor in
aquatic systems (McCarty and Secord, 1999), but no such favored passerine receptor
exists for terrestrial systems. In terrestrial risk assessments, a number of passerine
species have been utilized depending on habitat type and species applicability to site-
specific monitoring criteria. These species include: the European starling (Halbrook et

al., 1998), American robin (Turdus migratorius) (Henning et al., 1997; Henning et al.,

84

2002), red-winged blackbird (Agelaius phoeniceus) (Bishop et al., 1995), western
bluebird (Sialia mexicana) (Fair and Myers, 2002), ash-throated flycatcher (Myiarchus
cinerascens) (Fair and Myers, 2002), American redstart (Setophaga ruticilla), barn
swallow (Hirundo rustica), eastern phoebe (Sayornis phoebe), rose-breasted grosbeak
(Pheucticus ludovicanus), wood thrush (Hylocichla mustelina), and yellow warbler
(Dendroica petechia) (Henning et al., 1997). To our knowledge eastern bluebirds (Sialia
sialis) have been used infrequently as a reproductive monitor of exposure (Bishop et al.,
1995), and the house wren (Troglodytes aea’on) is a novel monitor of terrestrial PCB

exposure.

The house wren and eastern bluebird were selected as monitors of PCB exposure at the
Kalamazoo River Superfund Site based on a number of criteria. Eastern bluebirds and
house wrens frequently used nest boxes at the Kalamazoo River locations, so sample
sizes were expected to be sufficient to demonstrate population health. It was also
believed that the species’ exposure would coincide with local sources of contamination in
the soil due to their diet of terrestrial insects (Pinkowski, 1978), and thus, be useful .
surrogates to assess the potential reproductive impairment by PCBs. Here, we describe
productivity and growth of house wrens and eastern bluebirds located within the

Kalamazoo River Superfund Site and an upstream reference site.

85

MATERIALS AND METHODS

Site details

During 2000, nest boxes were established at two locations along the Kalamazoo River,
Michigan, 100-yr floodplain. The Fort Custer State Recreation Area (FC) is located
upstream of the sources of contamination, and therefore, was chosen to serve as a
background location due to the low background levels of contamination existing at the
site (Anonymous, 1997). Situated 67 km downstream, the target area was located at the
former Trowbridge Impoundment within the Kalamazoo River Area of Concern
(KRAOC), which was designated a Superfund site by the USEPA in 1986 (Figure 3.1).
The former Trowbridge Impoundment (TB) was formed when the Trowbridge Dam was
removed to the sill, which exposed some 132 ha of former depositional lake bottom

sediments.

86

:. , '9 I“:

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g ALLEGAN C TY r439
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m
E:
.1 FORT CUSTER STATE

RECREATION AREA

 

 

/

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T KALAMAZDOC TY

 

 

Figure 3.1. Map of the Kalamazoo River Area of Concern (KRAOC) and reference site.
The inset describes the location of the two counties in Michigan where reproductive
studies were conducted. A box designates the boundaries of the upstream reference

location (Fort Custer State Recreation Area) and the Trowbridge impoundment, located

within the KRAOC.

Previous studies quantified concentrations of total PCBS, DDT metabolites, and 2,3,7,8-
tetrachlorodibenzo-p-dioxin equivalents (TEQS) (Neigh et al., 2004b) based on World
Health Organization toxic equivalence factors (TEFWH0-Avian) (van den Berg et al., 1998).
111 311 tissues from both eastern bluebirds and house wrens, mean concentrations of total
P C 35 and TEQs were significantly greater at the KRAOC than they were at the reference

location’ F C (Table 3.1). Among all matrices, concentrations of total PCBs at TB were

87

39 to 122-fold greater than concentrations at FC, while concentrations of TEQS at TB

were 5 to 47-fold greater than concentrations at FC

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89

Productivity observations

Throughout the 2001 to 2003 nesting seasons, the nest boxes were monitored for
occupancy by eastern bluebirds and house wrens at PC (n = 64) and TB (n = 68). Boxes
were monitored daily to determine the date of clutch initiation and day of hatch.
Reproductive success was determined based on nest observations. Hatching success was
described as the percentage of eggs hatched in each nest. Fledging success was described
as the percentage of nestlings fledged per nestling hatched, and productivity was
described as the percentage of nestlings fledged per egg laid. Egg mass and length were
recorded within 24 h of laying. Day of hatch was also confirmed by assessing physical
development of the nestling (Pinkowski, 1975). Each nestling was examined for gross
external morphological abnormalities. Weight of each nestling was recorded on days 3,
9, and 12 (hatch day = day 0) for eastern bluebirds and on days 3, 6, and 9 for house
wrens. When chicks were sampled for contaminant analysis at approximately day 9 for
house wrens and day 12 for eastern bluebirds, each individual was weighed and the
length of the entire body (tip of beak to longest retrix), tarsus (tibiotarsal joint to hind toe
base), and unflattened wing chord were recorded. Measurements were taken during 2001

and 2002 for house wrens and from 2001 to 2003 for eastern bluebirds.

Statistical Analyses

For statistical analyses, each nest box was treated as a separate experimental unit and
values were reported on a per box basis. All nesting attempts were treated as separate

and individual observations. Normality was assessed with Kolmogorov-Smimov’s one

90

sample test with Lilliefors transformation, and homogeneity of variance was verified by F
test. All parametric data were analyzed by one-way analysis of variance (ANOVA), and
non-parametric data were analyzed by Mann-Whitney U or Kruskal-Wallis tests. The

criterion for significance used in all tests was p<0.05.

RESULTS

Reproductive success

A total of 34 house wren and 18 eastern bluebird nests were completed at the TB study
site and 71 house wren and 57 eastern bluebird nests were completed at the FC site over
the study period (Table 3.2). For the entire study, 32% of eastern bluebird nests failed
and 24% of house wren nests failed. The failure of the majority of eastern bluebird nests
was attributed to predation, which comprised over 50% of the nest failures at both FC and
TB. Abandomnent accounted for 29% of the nest failures at PC and 30% at TB. Failure
of house wren nests was attributed to a greater proportion of abandoned nests at TB (56%
of all failures), while at FC, no nest failures were attributed to abandonment. Predation

accounted for 44% of house wren nest failures at FC, but only 22% at TB.

91

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92

Both house wrens and eastern bluebirds can produce two broods in a season. Birds were
not banded at either location, and therefore, it was not possible to definitively determine
when a nesting pair established subsequent nests. In all years, there were 7 and 12
suspected house wren second broods at TB and FC, respectively, and 3 and 15 suspected
eastern bluebird second broods at TB and FC, respectively. Nests were still considered to
be independent samples because second broods could not be verified since adults were
not banded. In order to limit the effect of second nestings, reproductive parameters were
also evaluated based on dates of clutch initiation, where nests from early in the season
were grouped together and nests from late in the season were grouped together. Nesting
attempts were categorized as early or late nests to account for potential differences in
reproductive parameters between the first and second nestings. The median dates of
initiation for house wrens in 2001 were May 20 and June 24 for early and late nests,
respectively, and May 28 and July 1 during 2002, respectively. The median date of nest
initiation for eastern bluebirds was between April 21 and April 25 for early nests and June
9 and June 22 for late nests during the study. There was little correlation (Spearman, r2 <

0.10) between date of nesting and reproductive success in either house wrens or eastern

bluebirds.

All measures of reproductive success, including hatching success, fledging success, and
productivity were adjusted for fresh egg sampling, except clutch size, by eliminating the
egg collected for residue analyses from the reproductive analyses because the subsequent
potential fate of the eggs collected for residue analyses could not be predicted at the time

of sampling. Nests were observed for activity until the date of fledging, so it was

93

assumed that live sampled nestlings would have fledged successfully. Therefore, the
number of nestlings sampled did not affect the outcome of statistical analyses, but the
number of fresh eggs sampled could have affected the observed brood size and number of
fledglings. To make comparisons of brood size and the number of fledglings, a predicted
value was calculated based on other parameters. The brood size for each nest in which an
egg was sampled was calculated as the clutch size multiplied by the hatching success.
The predicted number of fledglings for each nest in which an egg was sampled was
calculated as the clutch size multiplied by the productivity. All other interactions
attributed to the collection of eggs or nestlings were considered to be negligible as

compared to exposure to PCBS.

Due to small sample sizes, measurements of reproductive health in eastern bluebirds were
combined among all years. When years were combined, a statistically significant
difference between FC and TB in the productivity (Mann-Whitney U, p = 0.031) and
nearly statistically significant differences in hatching success (Mann-Whitney U, p =
0.093) and fledging success (Mann-Whitney U, p = 0.074) were observed (Table 3.3).
Statistically significant differences were detected in the date of clutch initiation, so to
eliminate interactions between date of initiation and reproductive success, all nests were
separated into one of two groups designated “early” or “late” nests. Reproductive
success was not statistically different in late nests, but the clutch size (Mann-Whitney U,
p = 0.003) and fledging success (Mann-Whitney U, p = 0.041) were statistically greater at

F C than at TB in early nests.

94

Reproductive parameters for house wrens were also not statistically different between
years, so all years were combined. When all years were combined, the only statistically
significant difference between locations was fledging success which was greater at TB
than it was at F C (Mann-Whitney U, p = 0.030) (Table 3.3). Although the date of clutch
initiation for eastern bluebirds and house wrens was not significantly different between
locations, clutches were separated into two classes, designated “early” and “late” nests, in
an attempt to minimize the effect that date may have on reproduction. In early clutches,
clutch size (Mann-Whitney U, p = 0.045), hatching success (Mann-Whitney U, p =
0.030), and predicted brood size (Mann-Whitney U, p = 0.032) were statistically greater

for nests at PC than at TB.

95

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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97

Egg measurements

No statistically significant differences in egg measurements among years were detected,
so years were combined. The mean weights of eggs of neither species were statistically
different between locations (Table 3.4). The mean length of house wren eggs was not
statistically different between sites, but eggs were significantly longer at F C than at TB
for eastern bluebird eggs (Student’s t-test, p = 0.026). Egg parameters were evaluated for
interaction with each other and with date of initiation based on ANCOVA. No
interactions between any parameters existed for house wren, but a statistically significant
correlation between weight and length did exist for eastern bluebirds (ANCOVA, p =
0.008), which changed the significance of the comparison of mean egg length (p = 0.026

to p = 0.061).

98

Table 3.4. Mean (:1: 1 SD)a reproductive endpoints for eastern bluebird and house wren
eggs and nestlings reared at the Fort Custer State Recreation Area and at the Trowbridge

Impoundment along the Kalamazoo River Area of Concern.

 

 

Fort Custer Trowbridge
Eastern House wren Eastern House wren
bluebird bluebird
Eggs
N 36 74 1 l 37
Egg weight (g) 3.22 (0.67) 1.46 (0.01) 3.01 (0.12) 1.51 (0.09)
N 34 74 l l 37

Egg length (mm) 21.4 (1.04) 16.9 (0.08) 20.6 (0.28)“ 16.8 (0.16)

Nestlings”
N 12 22 3 12
Body weight (g) 27.79 (2.04) 9.43 (0.81) 29.17 (2.03) 9.32 (1.39)

Body length (mm) 92.3 (6.2) 64.9 (6.2) 98.1 (14.6) 61.5 (4.2)
Tarsal length (mm) 19.3 (1.8) 16.8 (2.7) 19.7 (1.4) 16.2 (2.4)

Wing chord (mm) 49.9 (8.5) 23.1 (4.2) 47.9 (4.9) 24.4 (4.6)

g

a Mean values were calculated based on the mean measurements per nest for all nests.
b Eastern bluebird nestling measurements taken at day 12 and house wren nestling
measurements at day 8 or 9.

c Statistically different from Fort Custer population (Student’s t-test, p = 0.026).

99

Growth measurements and growth curves

Differences in growth parameters between years could not be evaluated due to small
sample sizes, so all years were combined. Growth parameters between 8 and 9 day-old
house wrens were similar, so ages were combined. Eastern bluebird growth
measurements consisted of nestlings at day 12. Correlations between grth parameters
within locations were taken into account when growth was evaluated between locations.
There were no significant correlations present for eastern bluebirds, but there were
several potential correlations for house wrens. The correlation between body length,
wing chord length, and tarsal length drove the difference in mean body length between
sites to a nearly statistically significant value (ANCOVA, p = 0.072), but no growth

parameters for either species were statistically different between sites (Table 3.4).

Growth of nestlings was compared between sites based on curves generated from nestling
mass as an indicator of stress on the species (Zach and Mayoh, 1982). A logistic grth
curve was fitted to nestling masses at each site. Growth curves, based on average
nestling mass for each box at each nestling day, were strikingly similar for both species at
both sites when all years were combined. Growth curves of house wrens, compared
between sites, overlapped over the entire nesting period (Figure 3.2). Growth curves for
eastern bluebirds followed a similar trajectory, but the curve was shifted toward greater

mean nestling weights at PC (Figure 3.3).

100

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Growth curves, based on average nestling mass gain over the nestling period, for the two
sites were compared statistically. Nestling mass between nestling day 3 and day 10 for
eastern bluebirds and day 2 and day 8 for house wrens were log-transformed and the
mass gained per day of life was compared between sites. House wren mass gain per day
was significantly different between years (ANOVA, p = 0.020), but that of eastern
bluebirds was not. House wren mass gain was significantly less at TB than at F C during
2002 (Student’s t-test, p = 0.044) but not during 2001. Eastern bluebird mass gain per
day was not different between sites in 2001 or 2003, but 2002 was significantly different

(Kruskal-Wallis, p = 0.013).

DISCUSSION

Reproductive success

Eastern bluebirds made fewer nesting attempts than house wrens at TB and F C, but
confounding factors such as vegetation structure and age of the nest trail may contribute
to this difference (Munro and Rounds, 1985). The bluebird box trail at PC has been
established for over 30 yr, which may cause an increase the number of returning adults
and nestlings to the site. An investigation of habitat suitability at both sites was
conducted using a habitat suitability model for the eastern bluebird (A. Neigh,
unpublished data). Habitat is not expected to influence house wren nesting attempts due
to the large availability of the house wren’s preferred edge habitat. Overall, habitat
suitability for bluebirds during the early spring was determined to be 30.5% :t 32.9 (mean

i: 1 SD) at PC and 42.3% i 34.1 at TB. Due to increasing vegetation height during mid-

103

summer, the HSI at TB decreased to 32.2% i 25.9. Although these values are
comparable, the dynamics of vegetative growth and local groundwater hydraulics during
portions of the nesting season may render substantial areas of TB unusable for nesting,
and therefore, less attractive to the species. The suitability for nest establishment is
greater at TB, but the percentage of suitable area characterized by certain cover types is
less at TB (14%) than at PC (26%), and the relationship becomes even more distinct
when evaluated in mid-summer when only 3% of the total TB site is suitable for eastern
bluebird nesting. The relatively high quality of the habitat at the sites limits the
interaction between habitat suitability and reproductive success, but the extent of the high
quality habitat is less at TB than at F C. This suggests that the lower occupancy at TB
could be a result of spatial limitations, but those individuals situated on the available

quality habitat would not likely be limited by habitat structure.

Abandonment rates for tree swallows have been reported to be greater at PCB
contaminated sites compared to less contaminated habitats (McCarty and Secord, 1999).
Little data for the bluebird or the house wren are available for abandonment rates at PCB
contaminated sites, except for the tree swallow. Abandonment rates of eastern bluebirds
and house wrens at the Kalamazoo River were between 0% and 25%, which was near the
range (4.5% to 23.7%) reported for uncontaminated populations of bluebirds (Rustad,
1972). Abandonment rates of eastern bluebirds may be partly attributed to interactions
with house wrens. House wrens are known to interfere with the nesting of other species
(Finch, 1990), and unlike other studies of this type, house wren nesting was not

discouraged. Abandoned nests had no physical damage to the structure of the nest, as is

104

the case in 85% of house wren predations (Belles-Isles and Picman, 1986), so abandoned
nests may have been improperly labeled as abandoned rather than associated with house
wren interference. Abandonment was not observed for house wrens at F C, but some
nests were abandoned at TB. Again, interactions among house wrens may have caused
abandonment without damage to the nest, where in some cases, as much as 89% of

unsuccessful nesting attempts have been linked to conspecific interference (Finch, 1990).

The date of clutch initiation did not affect the reproductive success of either house wrens
or eastern bluebirds. Some studies have reported that second clutches were not as likely
to be successful as first clutches, with only 21% of second nests producing fledglings
(Pinkowski, 1979). At the Kalamazoo River, there was no reduction in nest success in
the clutches classified as “late” nests, but it could not be determined which nests were in
fact second nests and which nests were late first nest attempts. Other studies also did not

find a correlation between Julian date and reproductive parameters (Fair and Myers,

2002).

PCBS may affect reproductive capacity by decreasing hatching success, possibly by
causing infertility of eggs (McCarty and Secord, 1999). Hatching success in early
clutches of housr wrens at TB was significantly less than at PC (Mann-Whitney U, p =
0.045), which was also observed in tree swallows from the Hudson River where hatching
success was 64-79% at contaminated sites and 93% at a reference location (Secord and
McCarty, 1997). Conversely, hatching success was not impaired at the Housatonic River
for several species of passerines exposed to elevated levels of PCBs with 87.4% of the

eggs hatching (Henning et al., 1997). Of the nonviable eggs at the Hudson River, 60%

105

were infertile, while the remaining nonviable egg mortality was attributed to the failure of
the embryo to develop and the death of the embryo (Mch and Secord, 1999).
Hatching success of both the bluebird and house wren at the Kalamazoo River is most
strongly correlated with productivity (Spearman, r2 = 0.78). Productivity was
significantly reduced in the eastern bluebird at TB, but this value is dependent on a single
female in 2001 that twice brooded unsuccessfully but did not abandon the eggs. This
female alone accounted for a 40% decrease in reproductive success at TB because only a
total of 5 nests were established by bluebirds during that year. If this one individual is
removed from the data set, the hatching success at TB for all nests increased by 10% and
the productivity increased by 9%. Productivity for all nests was no longer significantly
different between locations when the nest was removed from the analyses, but all other
statistical comparisons were similar to those made previously. Power to detect
differences in reproductive measurements between locations was generally less than an
acceptable limit for both species (l-B < 0.80) (Table 3.5). Sample sizes greater than
those observed at the Kalamazoo River would have been needed to detect a 20% decrease
in reproductive performance at TB compared to F C. Reproductive performance was
depressed at TB compared to FC, but measured concentrations of PCBs in the tissue and
diet of both species were below the threshold concentrations for effects (Neigh et al.,
2004b). Tissue concentrations and dietary exposure suggest little risk of PCBS eliciting

reproductive effects on the birds in this study, so the observed decrease in reproductive

success in these birds is likely a result of other factors present in the environment.

106

 

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The fledging success and growth of nestlings, which may be related to nestling survival,
has been associated with proximity to contamination (Fair et al., 2003). Fledging success
and growth over the entire study was not impaired in house wrens at TB compared to FC.
In eastern bluebird nests, fledging success was less at TB in early nests but not for all
clutches combined, and growth over the entire study was not different. Although grth
for both species was different in one year but not over the entire study, the recruitment of
the population, described as the predicted number of fledglings, was not different, so the
impact of one years reduction in growth to the sustainability of the population is thought
to be minimal. Some differences in fledging success and growth of nestlings were
observed in the house wren and eastern bluebird, but these differences were not prevalent
throughout the length of the study. Due to the inconsistency of results, nestling survival,
predicted in this study as fledging success and growth, could not be linked to exposure to

PCBS.

No data are available regarding reproductive measurements in the eastern bluebird or
house wren at other PCB contaminated sites to compare. All measures of reproductive
success for eastern bluebirds at the Kalamazoo River, except productivity at TB, were
similar to uncontaminated populations (Pinkowski, 1979). There is little information on
the reproductive success of unmanipulated house wren populations, but one population
had similar productivity to the Kalamazoo River house wren populations (Finch, 1989).
Other studies with greater tissue concentrations of PCBS in terrestrial species did not
observe reproductive effects (Bishop et al., 1995, Henning et al., 2002). The

observations made in our study, coupled with those made by others at both PCB-

108

contaminated and uncontaminated locations indicate that it was unlikely that the
concentrations of PCBS measured in birds at TB were causing any population-level

effects on survival of nestlings.

Egg measurements

It has been suggested that eggs containing PCBs may exhibit differential dimensions
(Fair and Myers, 2002) or mass compared to uncontaminated populations (Femie et al.,
2000). PCBS may contribute to the smaller volume of eggs in ash-throated flycatchers at
contaminated sites (Fair and Myers, 2002), but this difference was attributed to
interaction with the width parameter in the calculation of egg volume (Pinkowski, 1975).
Egg length but not width was evaluated in eggs at the Kalamazoo River, so differences in
egg length may not be predictive of PCB exposure. As for measurements of egg weight,
the yolk of eggs at PCB contaminated sites was found to be greater in mass than at
uncontaminated sites, with greater mass associated with greater lipid content (Femie et
al., 2000). When comparing fresh eggs, the lipid content in house wren eggs from TB
was not significantly greater than that of eggs from FC. Samples sizes of fresh eggs of
eastern bluebirds were insufficient for analysis. Natural variation in unexposed
populations of eastern bluebirds has been described as an egg size gradient ranging from
observably smaller eggs (mean length x mean width, 19.0 x 15.3 mm) to comparatively
larger eggs (22.4 x 17.7 mm). The natural variation inherent in egg size limits the
discernment of PCB-induced effects on egg size in this population, but it does not appear

that exposure to PCBS had any significant effects on the sizes of eggs.

109

Growth measurements

Growth curves generated for each species were similar between sites. Logistic curves
gave the best overall fit to the growth data of the Kalamazoo River, which is similar to
the results for other locations (Zach and Mayoh, 1982). There are no published growth
curves for house wren nestlings, but the relative similarity of curves for birds at TB and
FC, over the length of the study, suggests that growth was not affected by exposure to
PCBS. Growth curves for eastern bluebirds at the KRAOC were compared to an
uncontaminated population (Pinkowski, 1975), and the logistic curve at TB was similar to
the uncontaminated populations until day 8. From day 8 to day 10, the rate of weight
increase in Kalamazoo populations decreased relative to the uncontaminated site, but
weights coincided again by day 12. TB nestling growth during 2001 had the greatest
mean nestling mass at each day, but the least during 2002. There is no apparent reason
for the variation among years, but the inconsistent results among years may be associated
with small sample sizes at the site. Nestlings at TB had a curve similar to FC, but the
mass of nestlings at each day was less. When mass gain for each box over the nestling
period of all years was examined, there was no statistically significant difference between
TB and F C. The results of a study conducted at another location suggests that availability
of insects accounts for 18-51% of the variation, while unexplained variation (error)
accounted for a similar proportion (Quinney et al., 1986). Potential variations in error at
the Kalamazoo River locations may be associated with variation of individuals, egg
quality, or measurement error. Based on visual examination of growth curves and
statistical analysis of nestling growth expressed as mass gain per day, no consistent

differences in nestling growth were identified when evaluating nests over the entire study

110

period. Although some significant differences between sites existed when years are
evaluated separately, the differences were only found in one of the three years of the
study. Thus, it can be concluded that the exposure to PCBs at TB did not affect the rates

of growth of either bluebirds or house wrens.

CONCLUSION

Measures of growth and overall productivity were used to evaluate whether adverse
population-level effects were occurring in two terrestrial avian species exposed to PCBS
at the Kalamazoo River Superfund Site. While the values of some measures of
reproductive success of house wrens were significantly less at TB than at FC in some
years, overall fledging success, which is a predictor of population-level effects, was
greater at TB than at FC. Also during one year, growth of each species was less at TB
than F C, but when evaluated over the entire study period, growth of both species was not
significantly different between TB and FC. Other studies also examined reproductive
effects in terrestrial species due to PCB exposure and reported no observed effects at
concentrations greater than those contained in birds at the Kalamazoo River (Bishop et
al., 1995, Henning et al., 2002). Based on the results of the study on which we report
here and the results of other studies investigating the effects of PCBs on terrestrial
passerine birds, it can be concluded that it was unlikely that exposure to PCBS at the

Kalamazoo River Superfund site was having adverse effects.

Co-located studies were conducted in conjunction with the present study in order to

quantify the concentration of PCBs in the tissues and diets of Kalamazoo birds and to

111

compare various approaches to estimating risk (Neigh et al., 2004b; Neigh et al., 2004c).
Concentrations of PCBs and DDE were significantly greater in tissues of the eastern
bluebird (Sialia sialis) and house wren (Troglodytes aedon) at TB, which was the more
contaminated location, than birds at FC, which was the upstream reference area (Neigh et
al. 2004b). However, concentrations of PCBS in eggs and nestlings did not exceed a
threshold above which effects were expected. Concurrent studies also investigated
dietary exposure and determined that total PCBS in the diet of terrestrial species were less
than the threshold concentration to cause adverse effects on reproduction (Neigh et al.,
2004c). Concentrations of TEQS in the diet were in a range that, based on the most
conservative threshold determined from laboratory studies with other species, could
cause some adverse effects. However, it was determined that the threshold was not
exceeded when toxicity reference values based on a more appropriate field-derived
threshold were applied in the risk assessment. The assessment of risk for concentrations
in tissues and dietary exposure depend heavily on the threshold of effects, and since there
are no studies specifically dealing with the species examined here, there are uncertainties

associated with the choice of a threshold concentration, especially with dietary studies.

Even based on an approach to evaluate risk that includes three lines of evidence (tissue
concentrations, dietary exposure, and reproduction), it was difficult to definitively
determine if PCBS are eliciting effects on birds at the Kalamazoo River. The results of
the studies presented here suggest some reproductive impairment of eastern bluebirds and
house wrens at some locations of the Kalamazoo River, but other factors besides PCBS,

such as co-contaminants, habitat suitability, and prey availability, are likely causes for the

112

effects. Reproductive effects at the Kalamazoo River can not be decisively linked to
exposure to PCBS, and with the exception of the potentially conservative estimate of risk
based on exposure to non-ortho and mono—ortho-substituted PCBs, the tissue and dietary
lines of evidence arrive at similar conclusions of no unacceptable risk. Based on three
lines of evidence, the authors do not believe that terrestrial passerine species are exposed
to concentrations of PCBs in contaminated areas of the Kalamazoo River that may

contribute to the present or future risk of reproductive dysfunction.

113

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hydrocarbons and mercury in sediments, red-winged blackbirds (A gelaius phoeniceus)
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throated flycatchers: A landscape-contaminant perspective. Environ. Poll. 118, 321-330.

Fair, J.M., Myers, O.B., Ricklefs, R.E., 2003, Immune and growth response of western
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Fernie, K.J., Bortolotti, G.R., Smits, J .E., Wilson, J ., Drouillard, K.G., Bird, D.M., 2000.
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Finch, D.M., 1989. Relationships of surrounding riparian habitat to nest-box use and
reproductive outcome in house wrens. Condor 91, 848-859.

Finch, D.M., 1990. Effects of predation and competitor interference on nesting success of
house wrens and tree swallows. Condor 92, 674-687.

Giesy, J .P., Ludwig, J .P., Tillitt, DB, 1994. Deformities in birds of the Great Lakes
region: Assigning causality. Environ. Sci. Technol. 28, 128A-135A.

Halbrook, R., Woolf, A., Arenal, C., 1998. European Starling (Sturnus vulgaris): Avian
Model and Monitor of Contaminant and Remedial Effects at Crab Orchard National
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Henning, M.H., Ebert, E.S., Keenan, R.E., Martin, S.G., Duncan, J.W., 1997. Assessment

of effects of PCB-contaminated floodplain soils on reproductive success of insectivorous
songbirds. Chemosphere 34, 1 121-1 137.

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Henning, M., Robinson, S., Jenkins, K., 2002. Robin productivity in the Housatonic
Watershed. April 2002 Report. Arcadis G&M, Incorporated Report for General Electric
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L., Docherty, D.E., Erdman, T.C., 1989. Microcontaminants and reproductive

impairments of the Forster's tern on Green Bay, Lake Michigan-1983. Arch. Environ.
Contam. Toxicol. 18, 706-727.

Ludwig, J .P., Auman, H.J., Kurita, H., Ludwig, M.E., Campbell, L.M., Giesy, J.P., Tillitt,
D.E., Jones, P.D., Yamashita, N., Tanabe, S., Tatasukawa, R., 1993. Caspian tern

reproduction in the Saginaw Bay ecosystem following a lOO-year flood event. J. Great
Lakes Res. 19, 96-108.

McCarty, J .P., Secord, A.L., 1999. Reproductive ecology of tree swallows (Tachycineta
bicolor) with high Levels of polychlorinated biphenyl contamination. Environ. Toxicol.
Chem. 18, 1433-1439.

MDEQ, 2003. Final (Revised) Baseline Ecological Risk Assessment, Allied Paper, Inc.,
Portage Creek, Kalamazoo River Superfund Site. Report April 2003. 1-6-12. Prepared by
Camp, Dresser, and McKee for Michigan Department of Environmental Quality,
Remediation and Development Division, Lansing, MI.

Millsap, S.D., Blankenship, A.L., Bradley, P.W., Jones, P.D., Kay, D.P., Park, C.S.,
Zwiemik, M.J., Giesy, J .P., 2004. Comparison of risk assessment methodologies for
exposure of mink to PCBs on the Kalamazoo River, Michigan, USA. Environ. Toxicol.
Chem. In press.

Munro, H.L., Rounds, R.C., 1985. Selection of artificial nest sites by five sympatric
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Neigh, A.M., Zwiemik, M.J., Bradley, P.W., Kay, D.P., Park, C.S., Jones, P.D., Newsted,
J .L., Blankenship, A.L., Giesy, J .P., 2004a. Tree Swallow (T achycineta bicolor) exposure

to polychlorinated biphenyls at the Kalamazoo River Superfund Site. Environ. Toxicol.
Chem. Submitted.

Neigh, A.M., Zwiemik, M.J., Bradley, P.W., Kay, D.P., Jones, P.D., Holem, R.R.,
Blankenship, A.L., Newsted, J .L., Giesy, J.P., 2004b. Accumulation of polychlorinated
biphenyls (PCBS) from floodplain soils by passerine birds. Arch. Environ. Contam.
Toxicol. Submitted.

Neigh, A.M., Zwiemik, M.J., Blankenship, A.L., Bradley, P.W., Kay, D.P., MacCarroll,
M.A., Jones, P.D., Newsted J .L., Giesy J .P. 2004c. Multiple lines of evidence assessment
of PCBS in the diets of passerine birds at the Kalamazoo River Superfund Site, Michigan.
Environ. Toxicol. Chem. Submitted.

115

Pinkowski, BC, 1975. Growth and development of eastern bluebirds. Bird-Banding 46,
273-289.

Pinkowski, BC, 1978. Feeding of nestling and fledgling eastern bluebirds. Wilson Bull.
90, 84-98.

Pinkowski, BC, 1979. Annual productivity and its measurement in a multi-brooded
passerine, the eastern bluebird. Auk 96, 562-572.

Quinney, T.E., Hussell, D.J.T., Ankney, CD, 1986. Sources of variation in growth of
tree swallows. Auk 103, 389-400.

Rustad, O.Q., 1972. An eastern bluebird nesting study in south central Minnesota. Loon
44, 80-84. '

Secord, A.L., McCarty, J .P., 1997. Polychlorinated Biphenyl Contamination of Tree
Swallows in the Upper Hudson River Valley, New York. 1-50. US Fish and Wildlife
Service, New York Field Office, Cortland, NY.

van den Berg, M., Bimbaum, L., Bosveld, A.T.C., Brunstrom, B., Cook, P., Feeley, M.,
Giesy, J .P., Hanberg, A., Hasegawa, R., Kennedy, S.W., Kubiak, T., Larsen, J .C., van
Leeuwen, F.X.R., Liem, A.K.D., Nolt, C., Peterson, R.E., Poellinger, L., Safe, S.,
Schrenk, D., Tillitt, D., Tysklind, M., Younes, M., Waem, F., Zacharewski, T., 1998.
Toxic equivalency factors (TEFs) for PCBS, PCDDs, PCDFs for humans and wildlife.
Environ. Health Perspect. 106, 775-792.

Yamashita, N., Tanabe, S., Ludwig, J .P., Kurita, H., Ludwig, M.E., Tatsukawa, R., 1993.
Embryonic abnormalities and organochlorine contamination in double-crested
cormorants (Phalacrocorax auritus) and caspian terns (Hydroprogne caspia) from the

upper Great Lakes in 1988. Environ. Poll. 79, 163-173.

Zach, R., Mayoh, KR, 1982. Weight and feather grth of nestling tree swallows. Can.
J. Zool. 60, 1080-1090.

116

Chapter 4
Accumulation of polychlorinated biphenyls (PCBS) from floodplain

soils by passerine birds

Arianne M. Neigh 1, Matthew J. Zwiemik *, Alan L. Blankenship 1*, Patrick w. Bradleyl,

Denise P. Kay *, Paul D. Jones ”, Ryan R. Holem *, John L. Newsted 1, John P. Giesy ”5

TZoology Department, Center for Integrative Toxicology, National Food Safety and

Toxicology Center, Michigan State University, E. Lansing, MI 48824

*ENTRIX, Inc., Okemos, MI 48864

§Biology and Chemistry Department, City University of Hong Kong, Kowloon, Hong

Kong, SAR, China.

117

I.

ABSTRACT

Accumulation of polychlorinated biphenyls (PCBS) from floodplain soils and associated
invertebrate prey by two passerine birds were evaluated at two locations at the
Kalamazoo River Superfund Site in Michigan. Eggs, nestlings, and adults of the eastern
bluebird (Sialia sialis) and house wren (T roglodytes aedon) were collected at a PCB
contaminated site and a reference location on the Kalamazoo River, Michigan. In eastern
bluebird eggs and nestlings at the more contaminated location, mean concentrations (wet
weight) of total PCBS were 8.3 and 1.3 mg PCB/kg, respectively, and concentrations of
2,3,7,8-tetrachlorodibenzo-p—dioxin (TCDD) equivalents (TEQS) (wet weight) were 77
and 6.3 ng TEQ/kg, respectively. Eggs, nestlings, and adults of house wrens from the
contaminated location contained 6.3, 0.77, and 3.2 mg PCB/kg, respectively, and 400, 63,
and 110 ng TEQ/kg, respectively. Concentrations of total PCBS and TEQS in tissues at
the more contaminated location were significantly greater than concentrations in tissues
at the reference site for all tissue types of both species. Concentrations of PCBS in tissues
of both species were approximately 40-fold greater at the more contaminated location
compared to the upstream reference location. Concentrations of TEQS in eastern bluebird
tissues were 4 to 10-fold greater at the more contaminated location, while concentrations
of TEQS in house wrens were 40-fold greater at the more contaminated location.
Exposure of the two species studied were different, which suggests that terrestrial-based
insectivorous passerine species, foraging in the same area, may have differential exposure
to PCBs depending on specific foraging techniques and insect orders targeted. Despite

the greater accumulation of PCBs at the more contaminated location, the risk of exposure

118

 

,_—#... ,

to PCBS ti

  
 

quotients 1

reference :1

KC)“ 0rd5;

robin. Mull

 

to PCBs did not exceed the threshold for adverse effects at either location. Hazard
quotients (HQs) based on both total concentrations of PCBS and TEQS at both the

reference and more contaminated locations were both less than 1.0 for all samples.

Keywords: Eggs, Bioaccumulation, Birds, Eastern bluebird, House wren, American

robin, Multiple lines of evidence, Twin embryos

119

 

INTRODUCTION

The Kalamazoo River in southwestern Michigan was contaminated with PCBS when
carbonless copy paper was inadvertently mixed into the paper recycling process. In
1986, three dams were removed to their sill, which drained approximately 132 ha of
formerly impounded sediment to create a large and contiguous landmass of lowland
forests and marsh. Previous studies of the Kalamazoo River quantified concentrations of
PCBs in multiple matrices including: soil, sediment, plants, mink, and tree swallows
(Camp, Dresser, and McKee 2002; Millsap et al. 2004; Neigh et al. 2004a). Surveys of
in-stream surface sediment (0-10 cm) indicate that concentrations of PCBS range from
less than 0.001 mg PCB/kg, dry weight (dw) to 153 mg PCB/kg, dw with a mean PCB
concentration of ~ 3.0 mg PCB/kg, dw (BBL, Inc. 1994a, Weston, Inc. 2002). Passerine
birds with terrestrial diets were identified as receptors of concern due to the
contamination in the formerly impounded floodplain soils, but little was known about the
trophic transfer and bioavailability of organochlorines to upper food web insectivores.
Preliminary sampling quantified concentrations of PCBS in surfical floodplain soils (0-25
cm) of former impoundment to be less than 0.001 mg PCB/kg, dw to as great as 85 mg
PCB/kg, dw with mean values of ~ 11 mg PCB/kg, dw (BBL, Inc. 1994b, BBL, Inc.

1994c, BBL, Inc. 1994d).

The house wren and eastern bluebird were selected as upper trophic level monitors of
exposure to PCBS derived from contaminated soil at the Kalamazoo River Superfund

Site. The risk of potential effects on passerine health, due to exposure to PCBS existing

120

in Kalamazoo River floodplain soils, was estimated by comparing concentrations of
PCBs to established toxicity reference values (TRVs) for eggs, nestlings, and adults of
the house wren and eastern bluebird (Fairbrother 2003). The American robin was
identified as a receptor of concern during a baseline ecological risk assessment (Camp,
Dresser, and McKee 2002) due to modeled contamination levels in its omnivorous diet.
Likewise, eastern bluebirds, also in the Family Turdidae, feed on invertebrates in close
contact with contaminated soil during portions of their life cycles (Pinkowski 1978).
Thus, it was hypothesized that concentrations of PCBs in bluebird tissue would be
analogous to concentrations in American robin tissues. The house wren is primarily an
insectivorous species and was used here to determine risk to avian species with wholly
insectivorous diets. It was expected, based on a 2000 baseline study at the reference site
and at the contaminated site, that a sufficient number of nests that were easily identified

would be available for both the bluebird and the house wren (Neigh et al. 2004b).

This paper applies “top-down” methodology that is based on measured concentrations of
PCBs in eggs, nestlings and adults to establish exposure to avian species of the
Kalamazoo River. Exposure was quantified by congener-specific analysis of
approximately 100 PCB congeners, including non-ortho (coplanar) and mono-ortho
congeners, and was reported as total PCBs. In addition, 2,3,7,8 -tetrachlorodibenzo-p-
dioxin (TCDD) equivalents (TEQS) were calculated for PCBs based on relative potencies
for birds (TCDD-WHOM,“ (van den Berg et al., 1998). Concentrations of total PCBs were
intended to quantify potential exposure based on all measurable congeners in the

environment, while concentrations of non-ortho and mono-ortho congeners, reported as

121

 

avian-specific World Health Organization (WHO-Avian) TEQS, evaluated exposure
based on the additive toxicity of the PCB congeners known to interact with the Aromatic
hydrocarbon receptor (AhR). It has been postulated that the most sensitive measure of
toxic effects of PCBS is through the AhR-mediated pathway and that due to weathering of
the total PCB mixture, the TEQ approach is a more accurate method to estimate exposure

and potential toxic effects (Giesy and Kannan 1998).

Multiple lines of evidence were employed to characterize risk of exposure to PCBs in
terrestrial passerine populations. Concentrations of PCBs were significantly greater in
the diet of birds at the more contaminated location than in birds from the upstream
reference location (Neigh et al. 2004c). Concentrations of total PCBS were deemed to be
less than a threshold where effects would be expected, but concentrations of TEQSWHo-
Avian may exceed a level of effect. Co-located studies of reproductive performance of
passerine species were also conducted during the same time period and applied to the
overall evaluation of risk as an ancillary line of evidence (Neigh et al. 2004b, Neigh et al.
2004d). These studies of reproductive performance over a two-year period indicated that
house wren fledging success was significantly greater at Trowbridge (TB) compared to
Fort Custer (FC). Eastern bluebirds had significantly decreased productivity at the more
contaminated location relative to the reference location during the three-year study, but
30% of the decrease in productivity between locations can be linked to a single female.
Although reproductive abnormalities were seen in both species, the cause of the
depressed reproductive success was unlikely to be due to exposure to PCBS, but more

likely due to differences in habitat suitability, co-contaminants, or prey availability. The

122

final line of evidence, examined here, is the measured concentration of PCBS in tissues,
which were then compared to TRVs. The primary objectives of the present study were to
1) determine if concentrations of total PCBS and TEQSW}]Q_AVian in passerine tissues were
different between locations; 2) to determine if all avian species examined in this study
were equally exposed; and 3) to deterrnine whether the concentrations of PCBS in the
tissues of passerine birds exceeded concentrations that, based on TRVs, would be

expected to result in population-level adverse effects.

MATERIALS AND METHODS

Site details

Eggs, nestlings, and adults were collected from nest boxes at two locations on the
Kalamazoo River from 2001 to 2003 (Figure 4.1). The upstream reference location at the
Fort Custer State Recreation Area (FC) was minimally contaminated by PCBs (Neigh et
al. 2004a). The more contaminated location, the former Trowbridge Impoundment (TB),
was located 67 km downstream from the reference location. Further physical description

of the study sites and nest box locations were described elsewhere (Neigh et al. 2004b).

123

 

ALLEGAN COUNTY

 

MENT (KRAOC)

FORT CUSTER STATE
RECREATION AREA

/

LAKE MICHIGAN

 

 

 

 

C UN COUNTY

9
VI
5
E
A
m

 

 

T KALAMAZOO C(TJNTY

Figure 4.1. Map of the Kalamazoo River Area of Concern (KRAOC) and reference site.
The inset describes the location of the two counties in Michigan where studies were
conducted. A box designates the boundaries of the upstream reference location (Fort

Custer State Recreation Area) and the Trowbridge Impoundment, located within the

KRAOC.

Tissue sampling
Samples of eggs, nestlings, and adults were collected during spring and summer of 2001 ,
2002, and 2003. One predetermined sample was collected from each nest box for

determination of PCB and TEQ concentrations. In addition, abandoned and addled eggs,

dead adults, and dead nestlings were salvaged for additional measurements of

124

concentrations of PCBS and TEQS Fresh eggs were sampled 7 tolO d post-laying, and
nestlings were sampled 6 to 8 d prior to fledging. Adult house wrens were sampled

during 2002 and 2003 by mist net.

Chemical analysis

Eggs were prepared by removing the eggshell, so the yolk and albumen remained for
chemical analysis. Nestlings and adults were processed prior to chemical analysis by
removing feathers, beaks, wings, legs, and stomach contents, and then, homogenizing the

whole body in a solvent-rinsed grinder.

Concentrations of PCB congeners and o,p ’- and p,p ’-isomers of DDT, DDE, DDD were
determined by previously described methods (Nakata et al. 1998, Neigh et al. 2004a).
Total concentrations of PCBs were quantified by Perkin Elmer AutoSystem and Hewlett
Packard 5890 series 11 gas chromatographs equipped with 63Ni electron capture detectors.
The method detection limit (MDL) was estimated to be 1 x 10'3 mg PCB/kg, wet weight
(w). Total PCB concentrations were calculated as the sum of all resolved PCB
congeners and co-eluting congeners. Non-ortho-substituted PCB congeners (IUPAC
numbers 77, 81, 126, and 169) were separated from co-eluting congeners and
interferences by carbon column chromatography. Extracts containing the non-ortho-
substituted (coplanar) congeners were analyzed by gas chromatograph mass selective
detector (Hewlett Packard 5890 series 11 gas chromatograph) equipped with an HP 5972
series detector. Detection limits varied among samples, but the mean detection limit for

all samples was <100 ng/kg, w.

125

T EQ computation

TEQS in bird tissues were calculated by multiplying individual concentrations of AhR-
active PCB congeners by their respective bird-specific World Health Organization
(WHO-Avian) toxic equivalence factors (TEF) (van den Berg et al. 1998). Total
TEQWHQAVjan concentrations were calculated as the sum of detectable individual non-
ortho and mono-ortho PCB congeners (77, 81, 105, 118, 126, 156, 157, 167, and 169).
When at least one of the coplanar congeners could not be quantified due to interfering
compounds, with the exception of congener 169, the sample was removed from statistical
analyses. Congener 169 was not regularly detected in the samples. For congeners that
occurred at concentrations that were less than the limit of quantification (LOQ), a proxy
value of half the LOQ was assigned. Some mono-ortho congeners co-eluted with other
congeners, so in order to report the most conservative estimate, the total concentration of

the co-elution group was considered to belong to its respective mono-ortho congener.

Statistical Analyses

For statistical analyses, each nest box was treated as a separate experimental unit, and
values were reported on a per box basis. All nesting attempts were treated as separate
and individual observations. Normality was assessed with Kolmogorov-Smimov’s one
sample test with Lilliefors transformation, and homogeneity of variance was verified by F
test. All concentration data were log transformed before analyses. All parametric data

were analyzed by one-way analysis of variance (ANOVA), and non-parametric data were

126

analyzed by Mann-Whitney U or Kruskal-Wallis tests. The criterion for significance

used in all tests was p<0.05.

Bioaccumulation and accumulation rates

Bioaccumulation factors (BAFs) and accumulation ratios were calculated for total PCBs
and TEstnoMiafl as the lipid-normalized concentration in the upper trophic level
divided by the lipid-normalized concentration in the lower trophic level. Accumulation

was calculated based on live sampled adults and nestlings and fresh sampled eggs.

Accumulation rates were calculated to determine the mass of PCBs gained by the
nestlings over the nestling period. The mass of PCBs in the egg was subtracted from the
total mass in the nestlings. The accumulation rate was calculated as the difference in
total mass of PCBs and TEQSWH0-Avian between nestlings and eggs divided by the

nestlings’ days of life (Custer and Custer 1995).

Selection of toxicity reference values (TR Vs)

TRVs were derived from the results of studies reported in the literature. Studies were
chosen for terrestrial passerine species based on several criteria. The studies judged to be
the most suitable for TRV calculation used wildlife species chronically exposed over
sensitive life stages; evaluated endpoints ecologically relevant to PCB exposure; had

minimal co-contamination; and were multi-year studies.

127

f

Few studies are available for the species used in the current study except for an
examination of American robin exposure and effects at the Housatonic River, New York,
which found no correlation between reproduction and PCB concentrations (Henning et al.
2002). American robin eggs at the Housatonic site contained a mean concentration of
83.6 mg PCB/kg, ww. From this field study it can be concluded that the threshold for
effects of PCBs on robins is greater than 83.6 mg PCB/kg, ww. Studies of European
starlings (Sturnus vulgaris) were also considered for derivation of an appropriate TRV.
European starlings exhibited a decrease in parental attentiveness and increased mortality
at two PCB sites compared to a reference site when Aroclor 1254 concentrations (mean d:
1 SD) were 13.6 d: 2.9 mg PCB/kg, w in eggs, 5.9 i 0.8 mg PCB/kg, w in nestlings,
and 15.9 i 5.3 mg PCB/kg, w in adults (Halbrook et al. 1998). The study of starlings
did not report reduced hatching success, and similar embryo mortality was observed at
another study site contaminated with metals but with relatively low concentrations of
PCBs. It has been suggested that adult incubation anomalies or co-contamination by
dioxin may be leading to embryo mortality, so these ‘ egg concentrations are an
unacceptable basis for a TRV for the Kalamazoo River (Halbrook et al. 1998). Effects
found in adult starlings also may be affected by the fitness of nestlings, which may
reduce feeding calls, and therefore, affect parental care. The starling study fulfilled
several of criteria by taking place over several years; measuring ecologically relevant
endpoints; and measuring concentrations at critical life stages in a terrestrial wild avian
species. The confounding factors in the study by Halbrook et al. (1998) and the fact that
Henning et a1. (2002) did not observe abnormalities in reproduction at much greater

concentrations suggests that Henning et a1. (2002) may be a more appropriate choice for

128

the TRV based on the no observed adverse effect level (NOAEL). Selected TRVs are

reported (Table 4.1).

Table 4.1. Toxicity reference values based on the no observed adverse effect level

(N OAEL) for tissues of avian species at the Kalamazoo River.

 

 

Tissue-Based TRV Reference
Total PCBs (mg PCB/kg) 83.6 (Henning et al. 2002)
Total TEQ (ng TEQ/kg) 13000 (USEPA 2000)

 

129

The TRV selected as a threshold for effects based on concentrations of TEQSwnOMm
was that suggested by USEPA (2000). The study investigated concentrations of
TEQSwnamim in tree swallows at the Hudson River, New York, over a 2 yr period; was
conducted on a wild passerine birds; evaluated relevant ecological endpoints during
critical life stages; and co-contamination was considered to be inconsequential. Tree
swallows exhibited abnormal plumage, decreased hatching success, and increased
abandonment during one year, but these effects were not observed in the following year.
The inconsistency of effects over both years suggests that values from this study should
not be used as a LOAEL, but they are appropriate for a NOAEL. The greatest
concentration of TEQSwnGmm in the year without effects was 13 ug TEQ/kg, w. No

LOAEL could be established for TEQSWllO-Avian-

RESULTS

Gross morphology and abnormalities

There were no gross physiological abnormalities observed in nestlings or adults of either
species, but some egg abnormalities were present in house wrens. One house wren egg
from PC during 2001 contained two well-developed embryos at about 10 d of incubation.
The egg was believed to be addled when sampled from the location. To our knowledge,
this is the first report of twin embryos in a passerine bird, although, twin chicks have
been reported in the emu (Dromaius novaehollandiae) (Bassett et al. 1999). In addition

to the twin egg anomaly, the eggshells at five TB nests were irregular. One nest had

130

irregularly shaped eggs, best described as jellybean shaped. The adults eventually
abandoned the nest afier a short incubation period. In four other nests, the shells had a
bumpy irregular texture and seemed to be thinner than normal eggs, although, eggshell
thickness was not measured directly. Also, as soon as one day after laying, egg contents
were noticeably desiccated as determined by a marked weight loss, which supports the

observed decrease in eggshell thickness in some nests.

Total PCB concentrations in tissue

PCB concentrations in eggs, nestlings, and adults from TB were significantly greater than
those at the reference location (F C) (Student’s t-test or Kruskal-Wallis, p<0.001) for both
eastern bluebirds and house wrens (Table 4.2). For all tissues analyzed, concentrations of
PCBs were 39 to 118-fold greater at TB than at F C. The trend in concentration
differences between sites was the same when concentrations were lipid-normalized. In
general, eastern bluebirds at TB had the greatest concentrations of PCBs in eggs and
nestlings (Table 2), but the greatest tissue concentration in the study was measured in a

house wren egg from TB in 2002 (36 mg PCB/kg, w).

131

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132

DDT metabolites were detected in all egg samples from a random subset analyzed for
DDT concentrations. Concentrations of p,p’-DDE comprised 95% to 98% of the total
sum of all DDT metabolites in eastern bluebirds and house wrens. Total DDT is defined
as the sum of all isomers measured. Concentrations in eastern bluebirds were 7-fold
greater than in house wrens at PC and were 3-fold greater than house wrens at TB.
Concentrations of total DDT (mean i 1 SD) contained in eastern bluebird eggs were 2.1
i 1.1 mg DDT/kg, ww at TB and 1.5 i 1.8 mg DDT/kg, ww at FC, but differences
between sites were not statistically significant. House wren eggs at TB contained 0.66 i
0.87 mg DDT/kg, ww and eggs at PC contained 0.20 :t 0.21 mg DDT/kg, ww, but again,
differences between locations were not statistically significant. The only statistically
significant difference was for concentrations of p,p’ -DDD in eggs of house wrens
between sites (Student’s t-test, p=0.021), but sample sizes were small (n=10). Addled
eggs of eastern bluebirds at PC contained 2.6 times greater concentrations of lipid-
normalized total DDT than fresh eggs, but addled eggs of eastern bluebirds at TB had
lipid-normalized total DDT concentrations 82% that of fresh eggs from TB. Addled eggs
of house wrens had lipid-normalized concentrations 7.4 and 5.7 times greater than fresh
eggs at PC and TB, respectively. Samples sizes were insufficient to perform statistical

tests comparing addled and fresh eggs.

T C DD Equivalents (T EQs WH0-AW'an)
Concentrations of 2,3,7,8 —TCDD equivalents (TEQSwnamm) were significantly greater
at TB than at FC for all tissue matrices in both species (Table 4.3). Concentrations of

TEQSWH0-Avian in the tissues of eastern bluebirds were 5 to lO-fold greater at TB than at

133

FC, while concentrations of TEQSWH0-AVjan in the tissues of house wrens were 15 to 47-
fold greater at TB compared to FC. An addled egg of a house wren contained the greatest

TEQWHO-AV.an concentration for all tissues in the study (2300 ng TEQ/kg, w).

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The relative contributions of non-ortho and mono-ortho congeners to total TEstuGMm
were evaluated at each site. PCB 169 was not detected in 67% to 69% of all samples for
eastern bluebirds and house wrens, and in the samples in which it was detected, it
represented less than 1% of the total concentration of the TEQWH0-Avian. House wren
tissues from TB were the only matrix in which PCB congeners 77, 81, and 126 were all
detected in the majority of the samples. PCB 77, 81, and 126 comprised the greatest
proportion of the total TEanO/wm for all species (Figure 4.2). In house wrens at FC,
PCB 126 comprised the greatest portion of the total TEanoAvmn, but at TB, PCB 77
made the greatest contribution to the concentration of the TEQWHOAVm. Contributions of
every congener to the total TEQWHO-Avian were significantly different between FC and TB
for house wrens. In eastern bluebirds, both PCB 81 and PCB 126 comprised significantly
different proportions of the TEQwquvim between sites, but PCB 77 was similar between
locations. PCB 118 was frequently detected at both locations in all samples for each

species.

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Figure 4.2. Contribution of individual non—ortho and mono-ortho congeners to total
2,3,7,8 TCDD equivalents (TEQS) in the tissues of passerine species at the Fort Custer

State Recreation Area (FC) and the Trowbridge Impoundment (TB).

Bioaccumulation

Ratios of concentrations between life stages of avian species for lipid-normalized total
PCBS and TEQSWH0-AVian were less than 1.0 for house wren eggs to nestlings, greater than
1 -0 for house wren nestlings to adults, and near 1.0 for house wren adults to eggs at FC
and TB. Eastern bluebird egg to nestling ratios (<].0) were less than those in house
Wrens (Table 4.4). Ratios of bioaccumulation between egg and nestling life stages for
eastern bluebirds and house wrens were greater at FC than for TB when comparing

TEQSWHO-Avian-

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Daily accumulation rates were calculated based on total PCBS and TEQSWHQAVian. Total
PCB daily accumulation rates for house wren nests were 0.0068 pg PCB/d, ww at PC
during 2001 and were 0.32 and 0.40 pg PCB/d, ww at TB during 2001 and 2002,
respectively. Daily accumulation rates based on TEQSWHGMam were 1.9 pg TEQ/d, ww
at PC during 2001 and 26 and 16 pg TEQ/d, ww at TB during 2001 and 2002,
respectively. Accumulation rates for eastern bluebirds at PC were 0.0053 and 0.054 pg
PCB/d, w for 2002 and 2003, respectively. Total TEQWHQAvian accumulation rates for

eastern bluebirds were 2.1 and 12 pg TEQ/d, ww at PC during 2002 and 2003,

respectively.

Relative potency (ng TEQS/kg PCB) of PCB mixtures in samples were calculated by
dividing the concentration of TEQSWHGMan by the concentration of total PCBS for each
sample (Table 4.3). The resulting relative potency is an indicator of the overall effect of
environmental weathering and differential bioaccumulation on the toxicity of the PCB
mixture: Relative potencies were generally greater and more variable at F C than at TB
for both species because concentrations of PCBS were generally low and concentrations
of TEQSWH0-AVian were driven by the detection limit of the analytical method. Ratios of
relative potencies among different sample types reflect changes in the potency of the
PCB mixture. At TB, the potency ratio from egg to nestling was 1.3 and 1.8 for eastern
bluebird and house wren, respectively, and the potency ratio at TB for the same life
Stages of these species was 3.3 and 0.45. Ratios for nestling to adult were 0.48 at TB and

l .4 at F C for house wrens.

I40

DISCUSSION

Gross morphology and abnormalities
A proportion of house wren nests contained eggs with shells that appeared to be thinned
(4% of all nests, 12% of nests at TB), although the thickness of the shells was not
measured. Eggshell thinning is a well-known result of DDT exposure (Ratcliffe 1967,
I-Iickey and Anderson 1968, Lincer 1975, Peakall 1993), but most studies observed no
correlation between PCB exposure and eggshell thickness (Dahlgren and Linder 1972,
Weseloh et al. 1989, Secord and McCarty 1997, Fernie et al. 2000). Although, at one
PCB contaminated site, eastern bluebird eggshells had a thinner eggshell thickness index
than at a reference location (Fair and Myers 2002). Total DDT residue levels were 1.3
mg DDT/kg in the attended eggs of another passerine bird, the tree swallow, and 2.8 mg
DDT/kg in unattended eggs, but these concentrations were not associated with decreases
in eggshell thickness between attended and unattended eggs or between the study
population and historical eggshell measurements prior to 1915 (DeWesse et al. 1985). A
concentration of 2.0 mg DDE/kg in eggs has been suggested as a threshold for effects in

bald eagles (Haliaeetus leucocephalus) (Elliot and Harris 2002).

Although little is known about the differences in species sensitivity between other birds
and the eastern bluebirds or house wrens, concentrations of DDE and DDT in the eggs of
eastern bluebirds were near the threshold for effect of other species, but the eggs of house
Wrens had concentrations of total DDT 3-fold less than the threshold. Thinning was not

observed in the eggs of eastern bluebirds, but thinning was observed in the eggs of house

141

wrens from TB. Unless the eggshells of house wrens are much more sensitive to thinning
caused by DDT than those of tree swallows, raptors or eastern bluebirds, the house wrens
does not appear to be at risk for DDT-induced eggshell thinning. However, studies do
find a magnitude of difference in the sensitivity of some terrestrial passerine species
(Eeva and Lehikoinen 1995, Blus 1996), so it is possible that house wrens are more
sensitive to the effects of DDT exposure than eastern bluebirds. No decisive conclusion
as to the cause of the abnormal eggs can be garnered from the study due to the lack of
data on concentrations of total DDT in abnormally formed eggs, the lack of measurement

of eggshell thickness, and the existence of co-contaminants in the area.

In addition, eggs at TB with thinned shells appeared to be desiccated. A similar
desiccation of eggs with thinned shells was associated with mortality of the embryo
(Eeva and Lehikoinen 1995). At the PCB contaminated Hudson River, the failure of eggs
to hatch was attributed mainly to lack of fertility instead of embryo mortality (McCarty
and Secord 1999). The reason for failure of individual eggs at the Kalamazoo River sites
was not specifically examined, but eggs with apparently thin shells did not hatch
successfully in most cases. The threshold for effects of DDT on reproduction of
passerine birds is likely near 8 or 9 mg DDE/kg (see DeWesse et al. 1985). No eggs of
either species at the Kalamazoo River contained concentrations of DDE greater than the
threshold, and mean concentrations were 4-fold less than the threshold. DDT is a co-
contaminant at many locations, including the Kalamazoo River Area of Concern
(KRAOC), which makes it difficult to attribute reproductive abnormalities to the

presence of one contaminant versus another. There was DDT detected at both

142

Kalamazoo River locations, but the presence of DDT is not expected to be causing

reproductive impairment in the species examined.

Total PCBS

Limited data are available for passerine birds exposed to PCBS through terrestrial diets to
which the results of this study could be compared. Tissue concentrations were similar
between species at F C and other species at other relatively uncontaminated sites in the
region (Bishop et al. 1995, Henning et al. 2002). Total concentrations of PCBS in house
wren and eastern bluebird eggs and nestlings at TB were less than concentrations
contained in American robin eggs and nestlings at the Housatonic River (Henning et al.
2002), but concentrations of PCBS at TB were greater than concentrations in red-winged
blackbird (Agelaius phoeniceus) eggs at locations in the Great Lakes-St. Lawrence River
Basin with the exception of one site (Bishop et al. 1995). Although few comparisons to
other studies can be made for these specific species, the fact remains that concentrations
of total PCBS were significantly greater at TB than at PC in all matrices examined.
Concentrations in the tissues corresponded to greater concentrations of total PCBS in the
soil at TB compared to FC (MDEQ 2003), which suggests that concentrations in the

tissues of the species examined reflect local contamination in the soil.

Tissue concentrations, expressed on a wet weight basis, were generally greater in eastern
bluebirds than house wrens. When concentrations in all matrices were lipid normalized,
concentrations in house wrens and eastern bluebirds were more similar, but eastern

bluebirds still contained greater mean total concentrations of PCBS. Differences in

M3

concentrations of PCBS between house wrens and eastern bluebirds were likely indicative
of on-site dietary exposure. For eggs and nestlings at TB, eastern bluebirds contained
total PCB concentrations 1.7-fold greater than house wrens. When site-specific average
potential daily doses were calculated for TB, exposure in the diet of eastern bluebirds was
found to be 3.7-fold greater than that of house wrens (Neigh et al. 2004c). At FC, this
study measured greater daily accumulation rates for the nestlings of house wrens
compared to eastern bluebirds, which suggests that they obtain greater concentrations
from the diet at FC. Indeed, dietary exposure for house wrens was greater than in eastern
bluebirds at FC. Further study is needed, but general trends in concentration tissue

gradients, described as daily accumulation rates, appear to reflect daily dietary exposure.

TEQSWHaAw-an concentrations

One measure of the toxicity of PCBS is based on toxic equivalency factors, which
compares the toxicity of individual PCB congeners to 2,3,7,8 -TCDD (Giesy and Kannan
1998). The greatest TEQWHOAWan values were consistently measured in adults and eggs
of house wrens from TB. This was opposite of what was measured for concentrations of
total PCBS for which eastern bluebirds contained consistently greater concentrations in
their tissues than house wrens. Mono-ortho and non-ortho (coplanar) congeners, which
comprise TEanamm concentrations, apparently accumulate between life stages to a
greater degree in house wrens than in eastern bluebirds. House wrens had concentrations
of TEQSWHO-Avian in eggs 5.7 times greater than in eastern bluebird eggs, and house wren
nestlings contained concentrations of TEQSwnGmm 10 times greater than in eastern

bluebird nestlings. Bioaccumulation factors from the diet to tissues (calculated from

144

 

Neigh et al. 2004c) also suggest that accumulation of both TEQSwuamm and total PCBS
were greater in house wrens than in eastern bluebirds, especially at TB (Table 4.5).
Unlike the relationship between total PCB concentrations and dietary exposure,
TEQSWHGAVian for dietary exposures do not correspond with tissue concentrations or
accumulation rates. Eastern bluebirds were found to have greater accumulation rates and

dietary exposure to TEQSwnomm compared to house wrens at both TB and F C (Neigh et

al. 2004c).

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146

The congener contributing the greatest proportion of the TEQWHQAVim was different at
the two sites. Congeners 81 and 126 contributed more to the total TEQS at PC than at TB
for both species. However, these congeners were detected in less than 30% of the
samples from FC, so the detection limit of each congener contributed greatly to the
analyses, being that half the detection limit was used to calculate contributions in the
remaining samples. Congener 77 was the greatest contributor in most matrices at TB.
The contribution of congener 77 to total TEQSWHgAvim increased from eggs to nestlings
of house wrens, but it decreased from eggs to nestlings in eastern bluebirds. Congener
126 followed an opposite trend by contributing more to the total TEQWHQAyim between
eggs and nestlings in eastern bluebirds and contributing less between eggs and nestlings
in house wrens. Adult concentrations did not follow any discernible trend. Adults are
likely exposed to variety of contamination sources over a life, while patterns in nestlings

more closely reflect local sources of contamination (Bishop et al. 1995, Secord et al.

1999).

Bioaccumulation

Ratios of accumulation were similar for terrestrial species and tree swallows from the
same location (Neigh et al. 2004a). Ratios ranging from 2 to 5 between nestlings and
adults suggest that birds are accumulating PCBS from their diet, but ratios less than 1.0
between eggs and nestlings suggest that the concentration or the rate of consumption is
not great enough in nestlings to overcome growth dilution. Red-winged blackbirds also
followed a similar trend with eggs having greater concentrations than nestlings (Bishop et

al. 1995). The greater accumulation ratio at PC compared to TB between eggs and

147

nestlings for eastern bluebird and house wren may be a result of variation around the

limits of detection for chemical analysis due to the small sample mass of many eggs.

Daily accumulation rates were calculated to describe the mass of PCBs accumulated by
the nestlings through the diet. House wrens at TB had accumulation rates over lO-fold
less than the accumulation rates for tree swallows at the same location (Neigh et al.
2004a) and at another location (Custer et al. 2003). Likewise, dietary exposure was
estimated to be 6 to 8-fold greater for concentrations of PCBS in the diet of the tree
swallow compared to the house wren (Neigh et al. 2004c). House wren and eastern
. bluebirds also had accumulation rates less than in black-crowned night heron (Nycticorax
nycticorax) and Forster’s tern (Sterna forsteri) (Ankely et al. 1993, Custer and Custer

1995)

Relative potency and potency ratios calculated for birds were intended to describe the
increase or decrease in toxicity of the PCB mixture at the study locations. Potency ratios
greater than 1.0 were observed for most comparisons which suggests that the mixture of
congeners in the food chain become more potent at increasingly greater trophic levels
through the bioaccumulation of AhR-active congeners (Trowbridge and Swackhamer
2002). Relative potencies at F C were influenced by several samples with low
concentrations of PCBs or concentrations of TEQSwnOAVm driven by the detection limit
of the analytical method. These scenarios led to greater relative potencies in F C samples
compared to TB, but the ratio of the relative potencies between trophic levels at each

location (potency ratio) was similar. Ubiquitous congeners such as PCB 118 and PCB

148

156 appear to bioaccumulate regardless of local sources of contamination, which
contributes to the overall concentrations of TEQSwrromm at the reference location. The
presence of these ubiquitous congeners in the diet adds to the increased potency of the
internal mixture as nestlings and adults feed. PCB 126 with a TEF of 0.] (van den Berg
et al. 1998), the greatest TEF for PCBs in avian species, contributes the greatest relative
percentage to the total TEQWHOAV,an concentrations in samples from F C. The
contribution of this congener also increases with trophic level, which suggests that PCB
126 is not easily metabolized and bioaccumulates through the food web. These factors
lead to the increase in relative potency between trophic levels at FC. At TB, PCB 77 and
PCB 126 contribute large portions to the total TEQWHGAvm due to the presence of these

congeners in the original mixture released at the site (Camp, Dresser, and McKee 2002).

Assessment of risk based on multiple lines of evidence

Multiple lines of evidence were utilized to assess the risk of PCB exposure to terrestrial
birds inhabiting the former impoundments at the Kalamazoo River Superfund site.
Exposure assessments of concentrations of PCBS in eggs, nestlings, and adults are
described here. A number of reproductive parameters and dietary exposures, calculated
as daily dietary dose, were also assessed for both eastern bluebirds and house wrens
(Neigh et al. 2004c, Neigh et al. 2004d). Potential adverse effects based on exposure
data were determined by calculating hazard quotients (HQs) derived from literature based
TRVs. All HQs at PC for total PCB and TEQSwuamm were less than 0.002 for all
tissues of house wrens and eastern bluebirds. Similarly, HQs at TB based on the mean

and U95 CL were less than 0.16 for all species and tissue types (Figure 4.3). In addition,

149

 

 

no individual tissue concentration of PCBS exceeded any of the threshold values for

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Hazard Quotient

 

 

 

Egg Nestling Egg Nestling Adult

I II I
I II I

Eastern bluebird House wren

Figure 4.3. Hazard quotients (HQ) for concentrations of total PCBs and 2,3,7,8 TCDD
equivalents (TEQS) based on the no observed adverse effect level (NOAEL) for house
wrens and eastern bluebirds at the Trowbridge Impoundment. Error bars indicate the

upper 95% confidence limit.

To assist in the evaluation of risk, dietary exposures, described in detail elsewhere (Neigh
et al. 2004c), were examined concurrently as another way of estimating exposure and
subsequent risk potential (Fairbrother 2003). Since there was little toxicity data available
for terrestrial passerine birds, dietary exposure studies reported risk based on a range of
HQ values. Concurrent studies suggest little risk to terrestrial passerines exposed to

concentration of total PCBs in the diet (Neigh et al. 2004c). Given this, the only

150

exposure calculations resulting in HQs greater than 1.0 were TEQSWH0-AVian in the diet of
eastern bluebirds and house wrens in the exposed area (TB) based on the most
conservative TRVs. HQ values, based on more appropriate TRVs calculated from field
measurements of PCBS in wild passerine birds (USEPA 2000), were less than the
threshold for effects based on the mean dietary exposure (Neigh et al. 2004c). It is
expected that actual risk lies somewhere within the range of calculated HQs, but that it
likely lies closer to the hazard based on the field measurements of wild passerine birds.
The presence of PCBs in tissues at concentrations that were less than a threshold for
effects, suggests that the HQ estimated based on dietary exposure of wild passerine birds

is likely a better estimate of risk.

The final line of evidence involving reproductive health suggested some reproductive
impairment that was likely attributable to other factors (Neigh et al. 2004d). Depressed
reproduction in house wrens and eastern bluebirds was observed in some, but not nesting
attempts, and in some, but not all parameters evaluated. Sample sizes were small,
especially for eastern bluebirds, and a 40% decrease in reproductive success at TB during
2001 can be attributed to a single female. Conversely fledging success, which is the most
important measure of reproductive success, was significantly greater in the PCB
contaminated area for house wrens. Similar field studies found that there was no
significant effect on reproductive performance of passerine birds at or concentrations
found in birds of the Kalamazoo River or even greater concentrations (Secord and
McCarty 1997; Custer et al. 2003). Likewise, studies of reproductive success conducted

at the Kalamazoo River did not find statistically significant decreases in reproductive

151

health of tree swallows at the contaminated TB location relative to the F C reference
location (Neigh et al. 2004b). Another study examined dioxin exposure to eastern
bluebird eggs, and no effects were observed at toxic equivalent concentrations greater
than those contained in bluebird eggs at the Kalamazoo River (Thiel et a1. 1997).
Without observing consistency across all nesting attempts and indices and because of the
contribution of a few adults to the reproductive measurements at TB, it can not be
concluded that the observed responses were due to exposure to PCBs, but rather were due
to other exogenous factors such as co-contaminants, habitat suitability, and prey

availability.

The results of the lines of evidence for exposure and effects in this study suggest that
concentrations of PCBS to which house wrens and eastern bluebirds were exposed are
less than the threshold for effects. Few studies have directly investigated the sensitivity
of these species to PCBS, so there are uncertainties as to the applicability of the species
used to derive the TRVs relative to the susceptibility to the effects of PCBs in the
terrestrial species in this study. Based on the lines of evidence, there does not appear to
be substantial risk of adverse effects due to exposure of terrestrial passerine birds to

PCBs originating the floodplain soils of the Kalamazoo River.

152

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Giesy JP (2004) Comparison of risk assessment methodologies for exposure of mink to
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PCBs at the Kalamazoo River Superfund Site. J Toxicol Environ Health Part A,
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PD, Newsted JL, Giesy JP (2004c) Multiple lines of evidence assessment of PCBS in the
diets of passerine birds at the Kalamazoo River Superfund Site, Michigan. Environ
Toxicol Chem, Submitted

Neigh AM, Zwiemik MJ, Bradley PW, Kay DP, Jones PD, Ruppert CA, Blankenship
AL, Newsted JL, Giesy JP (2004d) Reproductive success of passerines exposed to PCBs
through the terrestrial food web of the Kalamazoo River. Ecotoxicol Environ Safety,
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Secord AL, McCarty JP, Echols KR, Meadows JC, Gale RW, Tillitt DE (1999)
Polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p—dioxin equivalents in tree

swallows from the upper Hudson River, New York State, USA. Environ Toxicol Chem
18:2519-2525

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in the upper Hudson River valley, New York. Effects on breeding biology and
implications for other bird species. United States Fish and Wildlife Service, Cortland,
NY, USA

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Evaluation of the effects of dioxin-contaminated sludge on wild birds. Proceeding of the
TAPPI Environmental Conference

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hydrocarbon hydroxylase-inducing polychlorinated biphenyl congeners in the Lake
Michigan, USA, lower food web. Environ Toxicol Chem 21 :334-341

USEPA (2000) Revised Baseline Ecological Risk Assessment. Hudson River PCBS
Reassessment. Phase 2 Report. US. Environmental Protection Agency, Washington, DC,
USA

van den Berg M, Birnbaum L, Bosveld ATC, Brunstrom B, Cook P, Feeley M, Giesy JP,
Hanberg A, Hasegawa R, Kennedy SW, Kubiak T, Larsen JC, van Leeuwen FXR, Liem
AKD, Nolt C, Peterson RE, Poellinger L, Safe S, Schrenk D, Tillitt D, Tysklind M,
Younes M, Waem F, Zacharewski T (1998) Toxic Equivalency Factors (TEFs) for PCBS,
PCDDs, PCDFs for humans and wildlife. Environ Health Perspect 106:775-792

Weseloh DV, Custer TW, Braune BM (1989) Organochlorine contaminants in eggs of
common terns from the Canadian Great Lakes, 1981. Environ Pollut 59: 141-160

Weston, Inc. 2002. Removal assessment report for Allied Paper- Kalamazoo River site

Otsego/Plainwell, Michigan. TDD 0103-002. US. Environmental Protection Agency,
Washington, DC, USA.

156

Chapter 5
Multiple lines of evidence assessment of PCBs in the diets of passerine birds at the

Kalamazoo River Superfund Site, Michigan.

Neigh, A.M. 1, Zwiemik, MJ. T, Blankenship, AL. *1, Bradley, P.W. 1, Kay, D.P. 1,

MacCarroll, M.A. 1, Jones, P.D. t1, Newsted J.W. ‘, Giesy, J .Pm

J'Zoology Department, Center for Integrative Toxicology, National Food Safety and

Toxicology Center, Michigan State University, E. Lansing, MI 48824

‘ENTRIX, Inc., Okemos, MI 48864

§Biology and Chemistry Department, City University of Hong Kong, Kowloon, Hong

Kong, SAR, China

157

 

 

 

.11 Il11.11‘ .l' 11‘ I‘I I

ABSTRACT

Dietary exposures of passerine birds to polychlorinated biphenyls (PCBs) through the
terrestrial and aquatic food webs were examined at the Kalamazoo River, Michigan. The
tree swallow (T achycineta bicolor) represented those species with primarily insectivorous
aquatic diets, while the house wren (Troglodytes aedon), eastern bluebird (Sialia sialis),
and American robin (Turdus migratorius) were chosen to represent those with primarily
terrestrial diets. Average potential daily doses (APDDs) in site-specific diets were 6 to
29-fold and 16 to 35-fold greater at Trowbridge than at Fort Custer for total PCBs and
2,3,7,8 —tetrachlorodibenzo-p-dioxin (TCDD) equivalents (TEQS), respectively. This
study evaluated the risks of exposures of these birds to PCBS using both the “top-down”
(measured concentrations in tissues of birds) and “bottom-up” (predicted from
concentrations in the diet) approaches and compared the predicted effects with measured
reproductive fitness. Based on the best estimates of the threshold for effects in these
species, both the “top-down” approach based on concentrations of PCBs in the tissue and
the “bottom-up” approach based on dietary exposure suggest little risk of passerine birds
exhibiting effects expressed as total concentrations of PCBS or TEQs. Two of the three
species exhibited some reduction in reproductive success during some years at the
contaminated location relative to a reference location in some years. However, the
effects were not consistent from year to year, and when three years of pertinent measures
of reproductive success were considered, there were no statistically significant
differences in population-level reproductive outcomes, such as fledging success. Only

through the application of multiple lines of evidence can the best estimate of risk be

158

 

quantified. Both the “top-down” and “bottom-up” methods to estimate exposure based
on field-derived thresholds for effects, suggested little risk of PCBs to passerine birds at
the Kalamazoo River locations. These observations based on measures of exposure with
comparisons to TRVs developed from both laboratory and field studies were consistent

with direct measure of ecologically relevant endpoints of reproductive fitness.

Keywords: Birds, Reproduction, Bioaccumulation, Dietary exposure, House wren,

Eastern bluebird, American robin, Risk assessment, Trophic level

159

 

 

INTRODUCTION

The purpose of this study was to describe the exposure pathways for passerine birds
exposed to polychlorinated biphenyls (PCBs) at the Kalamazoo River and to estimate risk
associated with PCBS through those pathways. A secondary goal was to compare the two
established methodologies for estimating exposure and subsequent risk. Finally, the
results of the risk assessments based on the two methods of estimating exposure were
compared to measures of reproductive fitness at the more PCB-contaminated site and the
less contaminated, upstream reference location. The first method for estimating
exposure, the “top-down” approach, measured concentrations of PCBs in the eggs,
nestlings, and adults of each species. The other approach, which predicts exposure based
on concentrations of PCBs in dietary items, is referred to as “bottom-up” (Fairbrother
2003). The two approaches, although inherently linked, have become disjointed in the
risk evaluation process. The reason for this separation is ofien related to constraints on
funding and time, but the assessor can not be unequivocally assured that their selection of
methodology does not overlook some important interaction in determining risk, or for
that matter, does not over or underestimate risk based on uncertainties due to the

adjustment of models from the given data.

It has been suggested that several lines of evidence be used to evaluate risk instead of
implementing only one type of methodology (Fairbrother 2003). However, it may not
always be possible to apply both lines of evidence simultaneously. For this reason, the

levels of risk estimated by the two methods were compared so that in the future, assessors

160

will have an estimate of the similarity of the two methods. Based on this concept, a
system of evaluating representative species in all trophic levels of the ecosystem was
used to describe the complex dynamics present. This broad-based trophic level approach
generates a bottom-to-top description of contaminant exposure and effects in the system.
Detailed results of the top-down approach, including tissue concentrations and
measurements of reproductive fitness, are presented elsewhere (Neigh et al. 2004a, Neigh
et al. 2004b), but the degree of concordance between the top-down and bottom-up
approaches is evaluated in this paper. The first priorities of the study were to 1) estimate
risk to four passerine species based on dietary exposure; 2) to compare measures of
exposure based on a site-specific diet to exposure based on a literature-derived diet; and
3) to estimate the contribution of food web based exposure related to generalized feeding
guilds. Secondarily, this study examined the effectiveness of approaching a risk
assessment based on the examination of all trophic levels instead of choosing an
evaluation based solely on the top-down or bottom-up methodologies. Furthermore, the
results of the assessments based on the total concentration of PCBs or the TEQ were

compared and contrasted.

Exposures to PCBS and the potential effects of these exposures on passerine birds have
been examined in several aquatic ecosystems (Custer et al. 1998; Bishop et al. 1999;
McCarty and Secord 1999; Custer et al. 2003), but the effects on species exposed through
terrestrial food webs have been less well documented. Even fewer studies have evaluated
differential accumulations of PCBS by wildlife from contaminated media with the same

point of origin but environmentally weathered in substantially different ways. This study

161

was conducted to determine the differential sources of PCB dietary exposure, aquatic and
terrestrial, in order to quantify risk based on exposure parameters. The demarcation
between terrestrial and aquatic food webs within riverine systems is indistinct because of
the interaction between the two exposure pathways. In this manuscript, the aquatic
system was defined as the food web based on invertebrates with aquatic life stages
exposed through in-stream sediments. Species in a food web based primarily on plants
and invertebrates with essential terrestrial life stages will be referred to as the terrestrial

system.

The Kalamazoo River, Michigan, was designated a Superfund site in 1990 due to PCB
contamination released during the paper recycling process at multiple locations along its
banks (MDEQ 2003). Clays, inks, and paper fiber striped from recycled paper pulp were
originally deposited over in-stream sediment, but the area of contamination is now
partitioned between in-stream sediment, floodplain soils, and former impoundment
sediments. Floodplain soils became exposed through the frequent and regular flooding of
the river over its banks; the floodwaters exposing, carrying, and depositing sediments
over broad areas of the 100-year floodplain. An even greater source of terrestrial PCB
exposure originated from the removal of three dams from the river’s watercourse, which
led to the establishment of a terrestrial ecosystem when water levels were lowered and
former sediment exposed. Kalamazoo River wildlife can be exposed to PCBs via both
aquatic and terrestrial food chains due to this ubiquitous contamination of sediments and

vegetated former lake bottom soil.

162

Risks posed by exposure of insectivorous and omnivorous birds to PCBs within the
Kalamazoo River Superfund Site were evaluated through the use of four passerine birds.
These species were selected because they represent exposure to upper-trophic level
predators via different routes in the terrestrial and the aquatic food web. PCBs in the diet
are known to be persistent and bioaccumulative (Kannan et al. 1989) and can cause
reproductive impairment (Dahlgren et al. 1972), behavioral anomalies (Halbrook et al.
1998), and physiological abnormalities in offspring (Ludwig et al. 1993). The tree
swallow (T achycineta bicolor) was selected to monitor dietary exposure to passerines
primarily through the aquatic food web because it had been used in other studies and
found to be suitable (Ankley et al. 1993; Jones et al. 1993; Froese et al. 1998; Bishop et
al. 1999; McCarty and Secord 1999; Harris and Elliott 2000; Custer et a1. 2002), it
tolerates handling (Rendell and Robertson 1990), and individuals are relatively abundant
along the river. In a novel approach to risk assessment, the house wren (T roglodytes
aedon) was selected as an indicator of terrestrial food web exposure. Its ability to
colonize much of the habitat in the river basin and its abundance were important
determinants for choosing the species. The American robin (T urdus migratorius),
another terrestrial species, was chosen to represent omnivorous species and was also
considered to be maximally exposed to soil contaminants because of the large proportion
of earthworms, which are in direct contact with contaminated soil, in their diet. Finally,
the eastern bluebird (Sialia sialis) was selected for study because little is known about
PCB accumulation by this species, although there is a very large body of literature on its

biology.

163

 

MATERIALS AND METHODS

Site details

Two sites within the Kalamazoo River floodplain were selected for studies of passerine
birds, the Fort Custer State Recreation Area (FC) and former Trowbridge Impoundment
(TB). PC is an upstream reference area of known PCB sources, and TB is the most PCB
contaminated location within the Kalamazoo River Area of Concern (KRAOC) (Figure
5.1). The Trowbridge impoundment includes 132 ha of former sediments that are now
under natural vegetation. Nest boxes were established within the lOO-y floodplain in
both the Trowbridge Dam Impoundment and the Fort Custer State Recreation Area

reference location.

164

 

z

<

E ALLEGAN COUNTY

m

3 TROWBRIDGE

2 MENT (KRAOC)

L1]

:4

3 FORT CUSTER STATE
RECREATION AREA

 

 

 

 

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Figure 5.1. The PCB contaminated Trowbridge Impoundment within the Kalamazoo
River Area of Concern and an upstream reference location at the Fort Custer State

Recreation Area.

Bolus and tissue collection

Bolus samples were collected from individual nestlings (day 3 to day 14) during late
morning and early afiernoon at TB and FC to coincide with peak feeding periods (Kuerzi
1941). However, it has been suggested that the time of day does not strongly influence
the number of feeding visits by the parent, and the number of visits are comparable across
the breeding season (McCarty 2002). Ligatures were placed on all nestlings in each nest

according to Johnson et al. (1980) for l to 2 h to limit the effect of food deprivation on

165

growth. After placement of ligatures, nestlings were observed for several minutes to
determine if the ligature was affecting behavior of the adults or nesltings. Ligatures were
removed from nestlings that appeared to be disturbed by their presence. Each hour, the
nestlings’ throats and the inside of the nests were checked for boluses. The packaging of
the bolus in saliva by the adult prevented the loss of small dietary items through the
ligature. Once a bolus was collected from a nestling, the ligature was removed from that
nestling. Bolus sampling did not exceed four separate events or 3g of bolus material at
each nest. Sampling was discontinued when nestling tree swallows and eastern bluebirds
were 14 d or house wrens were 10 d to eliminate premature fledging. This method is
thought to provide an accurate representation of the nestling dietary composition
(Johnson et al. 1980). There were no cases of abandonment at nests in which bolus
sampling took place. Bolus collection did not statistically effect the grth of nestlings,
and there were no discernible differences in growth of nestlings between nests from

which a bolus was collected or not collected (Figure 5.2).

166

 

 

 

 

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The stomachs of the birds in the study were collected to describe dietary composition in
more detail. Tree swallow, eastern bluebird, and house wren nestlings were collected
from randomly chosen nests, euthanized by cervical dislocation, and frozen until
processing. Stomach contents were removed from nestlings and pooled based on
proximity to insect sampling grids. Detailed descriptions of sampling methods are

described elsewhere (Neigh et al. 2004a).

Average potential daily dose

The amount of PCBs ingested by passerine birds was calculated using the wildlife dose
equation for dietary exposures in the USEPA Exposure Factors Handbook (USEPA
1993). Average potential daily doses (APDD), calculated for total PCBs and 2,3,7,8-
tetrachlorodibenzo-p—dioxin (TCDD) equivalents (TEQS) based on World Health
Organization (WHO) toxic equivalency factors (van den Berg et al. 1998), were based on
site-specific and literature-based diets for tree swallows, eastern bluebirds, house wrens,
and American robins at the Kalamazoo River (Equation 1). Site-specific diets based on
bolus content and literature-based diets were used to estimate dietary composition of the
nestlings during the nestling period. Due to the lack of knowledge about the feeding
habits of adults and nestlings afier leaving the nest box, dietary dose only estimates site-

specific exposure to nestlings during the nesting period.
APDD = Z (Ck x F R., x NIRk) (Equation 1)

Ck = Concentration of PCBS (totals or TEQSWHQ-AVian, w) in the kth prey item in the

passerine diet.

168

 

F Rk = Fraction of the passerine diet based on mass represented by the k'h prey item.

NIRk = Normalized ingestion rate of k‘h prey item (g prey/ g body weight/day, ww).

Concentrations of PCBs in prey items were determined in insects collected in the bolus of
nestlings and during site-specific sampling of insect orders; the results of which are
reported elsewhere (Blankenship et al. 2004; Coady et al. 2004). F R., was determined
based on the dietary composition of each bird species. NIRk was derived from ingestion
rates reported for the American robin (0.89 g/g/d) and marsh wren (Cistothorus palustris)
(0.99 g/g/d) (USEPA 1993). Dietary composition was determined from bolus samples
based on occurrence and were converted to composition based on mass using the order-

specific weights of individual insects from each location within KRAOC.

Comparisons of risk based on dietary exposure to PCBs were based on hazard quotients
(HQs). Hazard quotients were calculated as the APDD (mg PCB/kg/d or ng TEQ/kg/d)

divided by the corresponding toxicity reference value (TRV).

Selection of toxicity reference values

TRVs were developed for the effects of PCBs based on both total PCB concentrations
and TEQSwnGmm in the diet and eggs. The selection of TRVs was based on several
criteria to determine their appropriateness for use in this study. These criterion included:
1) the use of wildlife species rather than traditional laboratory species; 2) chronic
exposure over sensitive life stages; 3) the evaluation of ecologically relevant endpoints;

4) minimal co-contamination; 5) multi-year studies; 6) and total PCB or TEQWHoAvian

169

values were reported or could be calculated. There were few studies available for
passerine species. Due to the uncertainty in the dose-response of passerine birds to PCB

exposure, a range of TRVs matching the given criteria have been reported (Table 5.1).

170

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171

A study in which ring-necked pheasants (Phasianus colchicus) were dosed with Aroclor
1254 was selected as an appropriate study from which to determine a threshold for effects
due to dietary exposure to PCBS during critical reproductive life stages (Dahlgren et al.
1972). Chick survival and egg production were adversely affected in the 50 mg PCB/wk
group, and hatchability was reduced by 14% in the 12.5 mg PCB/wk dose group
compared to the control. The calculated daily dietary dose based on the 12.5 mg PCB/wk
dose group and an adult pheasant weight of 1 kg (USEPA 1995) was 1.8 mg PCB/kg/d,
and this value was considered the lowest observed adverse effect level (LOAEL). The no
observed adverse effect level (NOAEL) of 0.6 mg PCB/kg/d was derived by dividing the
LOAEL by a safety factor of three. A safety factor of three was determined to be
acceptable because the LOAEL was established near the threshold for effects.
Galliformes are among the most sensitive avian species (Hoffman et al. 1996), so TRVs
based on Dahlgren et al. (1972) are expected to be a conservative estimate of the

threshold for effects in passerine species.

In addition to the laboratory study, TRVs for dietary exposure to total PCBS were
calculated from site-specific biomagnification factors (BMFs) between the diet and egg at
the Kalamazoo River. Decreased hatching success in pippers of tree swallows has been
reported to occur at 63 mg PCB/kg, w in eggs (Custer et al. 2003), but no reproductive
impairment of American robins was observed at 83.6 mg PCB/kg, w in eggs (Henning
et al. 2002). These studies are applicable to the current study because they fulfill the
criteria for TRV selection, and they are conducted on wild passerine birds. TRVs for

dietary exposure were calculated using biomagniflcation factors (BMFs) calculated by

172

dividing concentrations of PCBS in eggs at the Kalamazoo River by the weighted average
concentration of PCBS in the diet at the Kalamazoo River. For example, the site-specific
BMF from diet to egg of tree swallows is 4.3 (calculated from egg concentration of 5.1
mg PCB/kg, ww / concentration in diet of 1.2 mg PCB/kg, ww). When the
biomagnification factor (4.3) was applied to the LOAEL selected for eggs (63 mg
PCB/kg), a TRV of 14.7 mg PCB/kg for the diet was calculated. No LOAEL could be
established for terrestrial species, so the LOAEL calculated for tree swallows was used.
This same concept was applied to arrive at the most conservative estimate for all avian
species based on the NOAEL established for terrestrial passerine tissues, which was 83.6
mg PCB/kg, w in eggs (Henning et al. 2002). The most conservative estimate of a

TRV for dietary exposure when BMFs were applied was 1.9 mg PCB/kg, ww diet.

Few studies were available to derive TRVs based on TEanoAvim concentrations in the
diet of wildlife species, while even fewer studies exist for passerine birds. A laboratory
study by Nosek et al. (1992) found that intraperitoneal injections of 2,3,7,8 —TCDD at
concentrations of 1000 ng TCDD/kg/wk (140 ng TCDD/kg/d) caused a 64% decrease in
fertility and a 100% increase in embryo mortality in pheasants. The study was a
subchronic exposure (10 wk exposure period), and the length of the study was greater
than the length of time an adult passerine may spend on site before nesting (~ 5 wk)
(estimated from Adams 1979). Limitations of the study include the use of injections of
TCDD instead of feeding TCDD contaminated food to the test species and the evaluation
of TCDD exposure and not PCB exposure. It has been suggested that TEQS based on

PCBS may overestimate exposure relative to TCDD (Custer et al. 2004), so TRVs based

173

on TCDD exposure are likely to be conservatively estimate risk when applied to PCB
exposure. TRVs derived from Nosek et al. (1992) are also expected to be conservative
because the galliforrnes used in the study are among the more sensitive species to the
effects of TCDD (Hoffman et al. 1996). The NOAEL (14 ng TEQ/kg/d) was calculated
as by applying a safety factor of 10 to the LOAEL because effects due to the exposure are

pronounced in the test subjects.

TRVs for TEQWHWMan were also derived from site-specific BMFS. The NOAEL
selected for TEQWHOAWan in the tissues of birds was 13000 ng TEQ/kg (see Neigh et al.
2004b). This field study was based on tree swallows and fulfilled the criteria for TRV
selection. Based on the greatest BMF between diet and egg for the species examined in
this study (BMF = 13 for house wrens, Neigh et al. 2004b), the TRV for dietary exposure

to TEQS was determined to be 1000 ng TEQ/kg.

RESULTS

Dietary composition

The greatest number of bolus samples was collected during 2002. The most items were
collected from tree swallows and the fewest from house wrens. A total of 1476 items
from 64 nests were collected during the two years of diet collection in 2002 and 2003.
Data for dietary composition were combined between years and between grids to increase
the sample size and to provide a more representative account of passerine diets on the

Kalamazoo River over the course of the study. A total of 11, 9, and 11 insect and

174

 

 

 

invertebrate groups were represented in the bolus of the tree swallow, house wren, and
eastern bluebird, respectively. There were a total of fourteen invertebrate groups taken
by adult passerines including: diptera, trichoptera, ephemeroptera, orthoptera, neuroptera,
hymenoptera, araneae, odonata, hemiptera, lepidoptera, coleoptera, plecoptera, mollusca,
and isopoda. For the purpose of analysis, homoptera was combined with hemiptera.

Other items identified in the bolus were stones, glass, and pupae.

Aquatic insects made up the largest portion of insects in the bolus of tree swallows, and
were present in the bolus of all species in the following order: tree swallow (76.6%) >
eastern bluebird (46.73%) > house wren (6.25%). Dipteran species represented 60.6%,
5.0%, and 8.0% of the total diet of tree swallows, house wrens, and eastern bluebirds
(Figure 5.3). In contrast, diptera represented 79.1% and 80.0% of the aquatic species
taken in the diet for tree swallows and house wrens, respectively, while diptera only
comprised 17.1% of all aquatic species in the eastern bluebird. All dipterans were
lumped into the aquatic category because the majority of dipterans captured as adults
were of aquatic origin. Eastern bluebirds at TB also had a large aquatic component in the
diet, but this was largely due to one bolus with 63 trichopterans collected from TB.
When this was removed from the analysis, aquatic insects comprised 22.3% of the

eastern bluebird diet.

175

 

Tree swallow

 

Diptera
Trichoptera
Ephemeroptera

Odonata

 

Mollusca

House wren
lsopoda

Arachnida

 

Orthoptera

 

Lepidoptera

 

Hymenoptera

   

Coleooptera
Eastern bluebird

Hemiptera

Pupae

‘iIIEIII III%§ID

 

Neuroptera

 

 

 

 

 

 

 

Figure 5.3. Dietary composition based on occurrence at the Kalamazoo River.

The avian species examined differed in the occurrence of terrestrial insects in the diet
relative to aquatic insects. Unlike the eastern bluebird and house wren, tree swallows
contained a greater proportion of aquatic insects than terrestrial insects, and only the
terrestrial insect orders hemiptera and coleoptera represented more than 2% of the total
diet. The order orthoptera was important in the diet of both house wrens and eastern
bluebirds (house wrens = 16%; eastern bluebirds = 28%) but never occurred in tree

swallow boluses. Lepidoptera were infrequently taken by tree swallow adults (<0.05% of

176

diet), but comprised 34% and 10% of the house wren and eastern bluebird diet,

respectively.

The contents of nestling stomachs were also identified. Much of the content could not be
distinguished, but the indigestible portions, such as the legs, heads, and exoskeleton of
orders were identifiable. The purpose of identifying stomach contents was not to
quantify the diet using this method but was used to identify portions of the diet that were
not observed during bolus sampling. Describing diet solely through this method could
lead to bias because orders with indigestible portions would be easily identified, and
therefore, stomach contents would appear to contain a larger proportion of orders with
indigestible exoskeletons such as coleoptera (Wheelwright 1986). Sampling of stomach
contents from 2001 and 2002 revealed that stones and mollusks were frequently found in
the stomachs of nestlings, especially at FC, but large pieces of grit were not observed as
frequently in nestlings from TB. Of the nestlings examined at PC (n = 50), 64%
contained at least one stone and 10% contained at least on mollusk shell, while at TB (n =
11), 36% of the nestlings examined contained at least one stone and 18% contained a
mollusk shell. Seeds of the garlic mustard plant (Alliaria petiolata) were also found in

the stomachs of several eastern bluebird and house wren nestlings from PC (n = 3).

Average potential daily dose
Average potential daily dietary doses (APDDs) for passerine birds were calculated for
both total PCB and TEanGmm concentrations from each insect order for a diet based

on dietary composition at the Kalamazoo River. Based on the site-specific diet, dietary

177

ingestion of total PCBS and TEQSWHQAVian were greatest for the tree swallow and least for
house wren at TB (Table 5.2). Calculations of APDD for total PCBS were 10, 29, and 6-

fold greater at TB than at FC, and TEQSWHQ.A\.iam were 35, 26, 16-fold greater at TB than

FC in tree swallows, eastern bluebirds, and house wrens.

178

 

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179

Soil ingestion based on literature values was also factored into the calculation of the
APDD for total PCBS, but TEQWHO-AVjan concentrations in soils were not measured at the
site and could not be factored into the APDD. Concentrations of total PCBS in soils were
considered to be 85% bioavailable and contain 65% moisture (estimated from Studier and
Sevick 1992) to make the dry weight (dw) concentrations comparable to wet weight
concentrations in prey. The mass percent of grit in the diet consumed by the bird species
were calculated based on the average mass of grit in the stomach of nestlings over the
nestling period (tree swallow = 17.2 mg, dw; house wren = 6.2 mg, dw) (Mayoh and
Zach 1986). The APDD calculated with soil was not greatly different from the APDD
calculated with insects alone, but APDD calculated with soil was greater in all cases.
The APDD value for house wrens at TB was the most different with a 4% increase in
concentration when soil was added to the calculation of APDD. All other APDD values

did not change or increased by only 1-2% when soil was included.

The APDD was also calculated based on dietary composition found in the literature and
compared to site-specific calculations (Table 5.2). Soil ingestion was factored into the
calculation of APDD in both the literature diet and the site-specific diet for total PCBS
but not for TEQSWH0-AVjan. The APDDS based on total PCBS and TEstnaAvim for the
site-specific diet were no more than 4-fold greater than in the literature diet, which
suggests that the Kalamazoo River diet was similar to literature diets. The tree swallow
diet was the most different from the literature diet in APDD, and the house wren was the
only species in which the literature-derived diet yielded APDDs greater than those

calculated for the Kalamazoo River. A site-specific diet of the American robin was not

180

 

 

 

quantified in this study, but an APDD was calculated using a literature-derived diet. The
literature-derived ingestion of total PCBS and TEQSwnGmm for the American robin were
0.41 mg PCB/kg, ww and 52 ng TEQ/kg, ww, respectively. This suggests that the
exposure of the American robin is less than that of the tree swallow and eastern bluebird
but more than in the house wren. It should be noted that this study did not measure
concentrations of TEstngAvim in plants. Since the American robin diet contains 29%
plants (Howell 1940), the APDD for TEQSWHQAvian in the American robin diet may be

underestimated.

Assessment of risk

Hazard quotients (HQs) were calculated for each location based on the literature derived
APDD and the site-specific APDD. Two different estimates of the NOAEL and LOAEL
were calculated from TRVs derived from a laboratory study and from field studies. All
HQs at FC for total PCBS were less than 1.0 based on both the NOAELs and the
LOAELs. Therefore, only HQs at TB are discussed below. Mean values of HQs based
the NOAELs and LOAELs for total PCBS were less than 1.0 for all species, except for
the tree swallow site-specific diet, which had a HQ of 2.0 based on the most conservative
NOAEL (Figure 5.4). Species were also evaluated based on the upper 95% confidence
limit (U95 CL) in order to describe a range of HQs that could be expected for a
population. HQ values for all species at the U95 CL ranged from 4.8 for house wrens
based on the most conservative NOAEL to 0.17 for house wrens based on the less

conservative NOAEL. The HQs for all species based on the U95 CL for the LOAEL

l8l

ranged from 1.6 for house wrens to 0.02 for house wrens based on the less conservative

 

 

 

 

 

 

 

 
    

 

 

   

LOAEL.
- NOAEL(Dahlgrenetal1972)D LOAEL(Dahlgren etal. 1972)
NOAEL(Hennlngeta12002) I NOAEL(Custeretal. 2003)
Eastern bluebird Tree swallow House wren American
6 1 ll 4 t : robin
5 .
vO-D q-
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Figure 5.4. Passerine bird dietary hazard quotients for the Trowbridge Impoundment
(Kalamazoo) based on the total PCB no observed adverse effect level (N OAEL) and the
lowest observed adverse effect level (LOAEL). Dietary hazard quotients were calculated
based on the Kalamazoo site-specific diet and literature-derived diets. Error bars

represent the upper 95% confidence limit.

182

HQs based on TEQWHGAvim concentrations followed similar patterns as HQs based on
total concentrations of PCBS. HQs for FC were less than 1.0 for all comparisons, so only
values for TB are discussed. HQ values were greatest for tree swallows, and HQs of only
the tree swallow based on LOAEL exceed 1.0 (Figure 5.5). HQ values based on the most
conservative laboratory NOAEL (Nosek et al. 1992) exceeded 1.0 in all species, and in
tree swallows, the HQ value exceeded 10.0. The mean HQ did not exceed 0.20 based on
a less conservative NOAEL calculated from field studies on the tree swallow (calculated
from USEPA 2000). Based on the U95 CL of the NOAEL derived from Nosek et al.
(1992), HQs were as great as 70 in the tree swallow, but the greatest HQ calculated from

USEPA (2000) based on the U95 CL was 0.99 for tree swallows.

l83

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Eastern bluebird Tree swallow House wren American
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30% L
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based on the TEanoAvim no observed adverse effect level (NOAEL) and the lowest
observed adverse effect level (LOAEL) based on toxicity reference values calculated
from the literature. Dietary hazard quotients were calculated based on the Kalamazoo
site-specific diet and literature-derived diets. Error bars represent the upper 95%

confidence limit.

I84

DISCUSSION

Dietary composition

The bolus sampling strategy at the Kalamazoo River seemed to accurately predict the
general dietary feeding guilds of the species that were being evaluated, but it also
identified some unique feeding characteristics of each species. Tree swallows were
expected to feed primarily near the water’s surface on emergent aquatic insects (Quinney
and Ankney 1985, McCarty 1997). The tree swallows at the Kalamazoo River were
observed feeding in riparian areas and at the water’s surface, and the diet was comprised
of a majority of aquatic insects (76.6%). Dipteran species comprise a large portion of the
diet in tree swallows (60%), which is similar to a tree swallow population in New York
(57%) (McCarty and Winkler 1999) and Michigan (58%) (Johnson and Lombardo 2000).
Eastern bluebirds fed primarily on insects from terrestrial origins, as was expected
(Pinkowski 1978), but there were some deviations from the diet predicted by the
literature. Trichoptera was found in the diet of both tree swallow and eastern bluebird
populations at the Kalamazoo River, but was not represented in any of the literature-
derived diets (Figure 5.6). This likely resulted from the close proximity of Kalamazoo
populations to an aquatic ecosystem. There is also a notable absence of earthworms in
bolus contents of eastern bluebirds inhabiting riparian areas of the Kalamazoo River,
which is a likely result of unsuitable soil conditions for earthworms at study locations.
Previously, little was known about specifics of the house wren diet, but they also fell

within the terrestrial feeding guild as predicted.

I85

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The differences between the diet of the Kalamazoo River and other studies suggest that
although diets of each species may be predictably composed primarily of aquatic or
terrestrial prey items, there may be important site-specific interactions and opportunistic
sampling events that alter the general diet of a population. In the stomachs of nestlings,
there were stones, mollusk shells, bits of glass, and the seeds of the garlic mustard plant,
and likewise, metal shavings and plastic have been reported in the stomach of tree
swallows (Mayoh and Zach 1986). It is believed that all these items were
opportunistically accumulated as sources of grit. Ephemeroptera and trichoptera were
found in some boluses of eastern bluebirds at TB, which possibly shows that this species
will feed opportunistically. Diets may differ regionally or temporally depending on the
amount of opportunistically selected prey. These changes become important in the
calculation of exposure to contaminants at a site because the unique composition of a
site-specific diet may contribute significant concentrations to the overall assessment of
exposure, and therefore, pose significant risk that would not be recognized by applying

literature-based dietary composition to the assessment of risk.

Habitat dynamics may be a potential cause or even a tool to predict site-specific
differences in the diet of passerine birds. Habitat is a critical factor in the determination
of the diet of key receptors and the eventual determination of risk to those receptors. For
example, Blancher and McNicol (1991) examined tree swallow diet in relation to wetland
acidity. In wetlands with a high pH, tree swallows predominately preyed on mollusks
and ephemeroptera, but in wetlands with low pH, they preyed on a greater percentage of

diptera. The adult tree swallows also fed nestlings fewer aquatic orders relative to

187

terrestrial orders in areas of wetland acidity, which was possibly linked to the inability of
low calcium aquatic prey to satisfy the calcium requirements of nestlings (St. Louis and
Barlow 1993). In a case such as this, the exposure of tree swallows through terrestrial
pathways may be much more important than in a typical area. When diets are predicted
instead of measured, interactions between habitat and prey availability must be identified.
Only by measuring site-specific dietary composition or prey availability can these

interactions be taken into account.

Average potential daily dose

The intake of grit, or soil ingestion, was factored into calculations of the APDD as a
conservative approach to calculating risk. Concentrations in the soil could be relatively
great compared to concentrations in insects (soil = 4.3 mg PCB/kg, ww; insect = 0.55 mg
PCB/kg, ww), so potential exposure could be substantial depending on the amount of soil
ingested and the bioavailability of the PCBS through absorption in the gut. The majority
of the exposure to PCBS through grit ingestion is not eXpected to be from grit itself,
which is composed of stones, mollusk shells, and sand (Mayoh and Zach 1986), but from
soil associated with the surface of the grit. The amount of soil associated with the grit
surface is likely to be minimal in these species, especially when compared to domestic
ground feeding species such as the chicken (Gallus domesticus) or pheasant. Tree
swallows feed aerially, so the only soil present in the diet would exist as incidental
particles on prey or would be consumed in conjunction with grit particles. In addition to
grit ingeStion, eastern bluebird, house wrens, and American robins may ingest some

additional soil particles from the ground as they are feeding, but American robins likely

188

 

have the greatest soil ingestion of all species due to the ingestion of earthworms with soil
in the gut. This exposure pathway could potentially yield extensive exposure in species
consuming large amounts of soil, so soil intake should be carefully considered when

evaluating exposure in various species.

The APDD based on a theoretical diet derived from the literature was an underestimate of
theisite-s‘pecific diet in most species. The underestimation can be attributed to the
proportion of aquatic insects in the diet at the Kalamazoo River, relative to that of the
literature diet. The aquatic insects contain some of the greatest concentrations of PCBS
for insects of the Kalamazoo River (Coady et al. 2004), which results in the greater
concentrations of PCBs in the site-specific diet. Only for the house wren did the
literature diet contain greater concentrations than in the diet of the Kalamazoo River.
Lepidoptera and orthoptera contained lesser concentrations of total PCBs and TEstno-
Avian than all insect orders (Blankenship et al. 2004). Since the site-specific diet for house
wrens was comprised of a much greater proportion of lepidoptera and orthoptera (90% by
mass) than did the literature diet (20% by mass), the APDD calculated from the site-
specific diet was also less than the literature diet. The differences in the proportion of
insects may be a result of the fact that a literature diet could not be located for the house
wren, so a published diet for the marsh wren was used (Kale 1965). The differences
between the diets does not greatly effect the estimate of risk based on the mean
concentration in the diet, but based on the U95 CL, the most conservative HQ is 0.53

from the site-specific diet and 4.8 from the literature diet. Depending on the weight

189

given to this line of evidence during the risk evaluation process, a very different estimate

of risk may be reached, so it is critical to establish a diet specific to the species.

Relationship between risk estimates based on total PCBS and T EQs

Hazard quotients based on TEQSWHMW were greater than those based on total
concentrations of PCBS. HQs based on the total PCBS is thought to be a more accurate
estimate of possible risk since the concentration can be compared directly to values
reported in the studies from which TRVs were derived. There are difficulties and
uncertainties with assessing the toxicity of environmentally weathered PCB mixtures that
are quantified as Aroclors. Congener-specific analyses, including coplanar PCB
congeners combined with a calculation of TEQS, is generally thought to correlate better
with toxicity than measures of total PCBs (Giesy and Kannan 1998; Blankenship and
Giesy 2002). However, recent work by Custer et al. (Custer et al. 2004) calls into
question whether toxic equivalency factors (TEFs) developed for PCBS are appropriate to
predict effects in some bird species. One reason for the possible overestimate of risk
posed by complex mixtures of PCBS is that concentrations of TEQS are calculated by
multiplying each aromatic hydrocarbon receptor (AhR)—active PCB congener by a
relative potency expressed as a toxic equivalency factor (TEF). TEF values are
consensus values that were rounded up to be conservative estimates of risk (van den Berg
et al. 1998). Thus, they tend to overestimate the risk. This coupled with the use of proxy
values for congeners that were present at concentrations less than the method detection

limit were the most likely reasons that HQs estimated based on TEQs were much

WHO- Avian

greater than those estimated based on total PCBs. For example, based on tree swallow

studies on the Woonasquatucket River, an LCSO based on TEQS was estimated to be

190

1700 pg TEQ/g, ww (primarily due to TCDD) (Custer et al. 2004). However, if one
compares this LCSO to concentrations of TEQS (calculated from PCBS) between 1,730
and 12,700 pg TEQ/g, ww in tree swallow eggs from the Hudson River, one would
expect considerable population-level effects due to mortality. However, there were
minimal effects on subtle endpoints at TEQ concentrations (based on PCBS) in tree
swallow eggs from the Hudson River (McCarty and Secord 1999). In other words, a
concentration of TEQ was not toxicologically equivalent to the same concentration

expressed as calculated TEQs (based only on PCBS).

Assessment of risk using multiple lines of evidence

Little information on the toxicity of PCBs to passerine birds was available for terrestrial
diets; thus there was uncertainty associated with the selection of an appropriate TRV to
compare to Kalamazoo River dietary exposure. Wild passerine birds, such as the ones
examined in this study, appear to be less sensitive to PCB exposure than domesticated
galliformes on which dietary TRV‘ could be based (Hoffman et al. 1996). Thus, the
dietary HQs based on domesticated avian species are likely an overestimate of hazard
potential. In order to calculate a more realistic HQ based on similar species, site-specific
and species-specific BMFs were applied to TRV values chosen for tissue exposure at the
Kalamazoo River (Neigh et al. 2004a, Neigh et al. 2004b). The laboratory studies on
galliformes and the toxicity reference values based on Kalamazoo River BMFs are
intended to give a range of hazard quotients that expresses the most conservative estimate
of risk and also reports a value we feel is a more appropriate estimate of the true risk of
passerine birds exhibiting population level effects due to current contaminant levels at the

Kalamazoo River. Based on the most conservative HQs, there appears to be risk to

I91

passerine species exposed through the diet due to dietary concentrations being 13 times
greater than the threshold for effects. These values suggest that effects may occur due to
exposure to non-ortho and mono-ortho PCBs at the Kalamazoo River (USEPA 1998).
When the more realistic, field-based TRVs are applied, the HQs are near to or less than
1.0, which suggests little risk of the population exhibiting reproductive effects.
Additional lines of evidence should be evaluated in order to arrive at the best estimate of
risk, especially given the uncertainty in selecting appropriate TRVs. This information
coupled with the discussion above on the use of HQs based on TEQS indicate that the

more appropriate estimates of risk are those based on total PCB concentrations.

In order to assist in the evaluation of risk, other lines of evidence were examined for .
agreement with the analysis and calculation of risk from dietary exposure (F airbrother
2003) (Figure 5.7). Previously published studies on passerine birds inhabiting the
riparian area of the Kalamazoo River have examined other lines of evidence to quantify
site-specific risk to passerines (Neigh et al. 2004a; Neigh et al. 2004b; Neigh et al.
2004c, Neigh et al. 2004d). Studies using the top-down approach to evaluate egg,
nestling, and adult tissue concentrations in the Kalamazoo River tree swallows, eastern
bluebirds, house wrens, and American robins suggest that there is little risk to passerines
based on tissue concentrations at the site. Other field studies found that there were no
pronounced effects on the reproductive fitness of passerine birds at the concentrations of
PCBS measured in birds of the Kalamazoo River (Secord and McCarty 1997; Custer et al.

2003)

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A third line of evidence was used to investigate population health of passerine species in
contaminated portions of the Kalamazoo River compared to an upstream reference
location. Studies of reproductive performance did not find statistically significant
decreases in reproductive fitness of tree swallows at the more contaminated TB location
relative to the FC reference location. However, there were some measures of
reproductive success in the eastern bluebird (productivity) and house wren (clutch size,
brood size, and hatching success) that were statistically less at TB than FC, but these
differences were not found consistently across all of the reproductive measures or
throughout the entire nesting season (Neigh et al. 2004d). Also, samples sizes were small
for eastern bluebirds, and so, a 10% decrease in reproductive success at the contaminated
location during the study can be linked to a single female who made two unsuccessful

reproductive attempts during one year.

Guidelines based on criteria established for describing the chemical causation for effects
in ecoepidemiological studies were applied to this study to determine whether the
observed reproductive effects were likely caused by PCBs. They include temporality,
strength of association, consistency, and biological. plausibility (Hill 1965). PCB
contamination remained constant throughout the study but reproductive success varied
over the course of the field season, among years, and among species, so the first criterion
requiring consistent trends over the course of exposure (temporality) was not satisfied.
Also, strength of association between PCB exposure and reproductive effects could not
be identified. Some individuals with comparatively great concentrations of PCB

reproduced successfully, while other individuals with background levels of contaminants

I94

 

failed to reproduce. Consistency between results of available studies is also needed in
order to assign causality to PCBs for reproductive dysfunction in passerine birds. Few
studies have investigated dosing in a laboratory setting in these species, but there are
several studies available describing PCB concentrations in the field. Other field studies
of passerine species did not find significant reproductive effects when concentrations of
PCBs in tissues were similar or greater than in the birds at the Kalamazoo River .
(McCarty and Secord 1999, Harris and Elliot 2000, Henning et al. 2002), which suggests
that PCBs are not the primary causative agent of effects. It is biologically plausible based
on laboratory and field studies that PCBs deposited in the sediments can bioaccumulate
up the food chain and elicit effects on the reproduction of upper trophic level species
(Giesy et al. 1994). PCBS seem unlikely to be the primary cause of the observed
reproductive effects based on the criteria described due to the lack of temporality,
strength of association, and consistent findings of no effects at concentrations similar or
above those present at the Kalamazoo River. Although it can not be denied that PCBS
cause reproductive impairments at certain concentrations, the below-threshold
concentrations present in the tissues and diet at the Kalamazoo River suggest that other
factors such as co-contamination by DDT and its metabolites, habitat quality, inclement

weather, or prey abundance may be affecting reproduction.

There are several potential reasons for different conclusions between the lines of
evidence. The evaluation of risk from tissue and dietary concentrations depends heavily
on the selection of the TRV. Little data for these species exist based on concentrations of

total PCBS, but even less data exist on the dose-response of TEQSWH0-Avian in the tissue or

I95

 

 

diet and their relation to reproductive effects. Upon selection of a TRV, uncertainty
factors are often applied to compensate for unknown differences between species,
exposure time, or exposure route (Chapman et al. 1998). The application of these factors
is often an inexact science and can introduce a negative bias into the proper calculation of
TRVs, which would then result in an overestimate of risk. In particular, in the case of
PCBs, the use of total PCB concentrations as a measure or exposure, instead of TEQS
seems to more accurately represent the actual risk based on field measures of effects. A
strength of this study is that it used measured concentrations of PCBs to quantify
exposure in the diet and tissues instead of predicting exposure based on concentrations in
other matrices and then applying biomagnification factors to predict other trophic level or
life stage concentrations. As for the population health line of evidence, observations of
reproductive performance may also be affected by environmental stressors, which may be

confounded with exposure to PCBs.

CONCLUSION

Many factors can play a role in the calculation of risk, and by selecting only one method,
there is a possibility of missing an important interaction and improperly characterizing a
site. Three lines of evidence based on reproductive health, tissue concentrations, and
dietary exposure arrived at differing conclusions of risk. Overall, the various lines of
evidence suggest that the inconsistent differences in reproductive performance observed
for some species of passerine birds at the more contaminated site were caused by factors

other than exposure to PCBs. In addition, the top-down approach (concentrations

I96

measured in the tissues of the birds) suggested little risk to any species, but the bottom-up
approach (exposure predicted based on the diet) arrives at different conclusions of risk
depending on the TRV selected and whether they were based on concentrations of total
PCBs or TEQS. When exposure were predicted through application of biomagnification
factors, uncertainty factors, or if the appropriateness of the TRV is in question, the actual
dynamics at the site can become even more difficult to characterize. As suggested by
Fairbrother (2003), the application of several lines of evidence in multiple matrices seems
to be the best approach to gather the most complete and appropriate information on which
to gauge important risk decisions. By considering all of the lines of evidence
simultaneously, it was concluded that the current concentrations of PCBS in the aquatic
and terrestrial food chains were not causing population-level adverse effects on the

populations of passerine birds studied here.

I97

 

 

 

.Ii

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