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A STUDY OF THE NESTING OF THE GREEN
HERON (BUTORIDES VIRESCENS) IN

SOUTHERN MICHIGAN

Thesis for the Degree of M. S.
MICHIGAN STATE UNIVERSITY

James Clare Va nden Berge
196-0

      
     

  

LIBRARY

Michigan State
University

 

A STUDY OF THE TESTING OF

THE GREEN HERON (BUTCRIDES VIBESCT'") IN SOUTHERN MICHIGAN

‘
a .

By

James Clare Vanden Berge

AN ABSTRACT OF.A THESIS

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

MASTER OF SCIENCE

Department of Zoology
1960

U, 7' ) ' 3 _ “1:
Approved _C{:flfifl;f<- A. Jfi’:LLL£Lcc¢.
./‘ . ’
. 1/

ABSTRACT

A STUDY OF T-.E 1.13.37: z-IG OF
THE GREEN HERON (BUTCHEES VIRESOHTS) IN SOUTHERN MIOI—IIGAI-I

 

by James Clare Vanden Berge

The life history study of a nesting colony of Green Herons in
southern Michigan was carried out over a 2 year period.

Thirty-seven nests in the two successive years were located in
a small pine stand at the edge of a marsh succession bordering
Crooked Lake in Barry County. The plantation consisted of red,
Austrian, and white pine.

The average height of the nests was 11.7 feet with a standard
deviation of 1.5 feet. The average height in the red and Austrian
pine was the same as in the white pine. There was a significant
difference in the standard deviations however. Three nests were
found in trees or shrubs other than pine. No tree contained more than
one nest during the same season.

The average clutch size in this study was 5.5 eggs. The average
size of the eggs was 59.1 x 29.9 mm. The only determination of the
time of laying was that of a third egg laid between 12:00 and #:00 PM,
May 29, 1959. The incubation period for 10 eggs was 25 days.

The nestling period extends to 10 days after hatching. Weights
of the young were taken to show their growth during this period.

The young are fed by regurgitation. The food consisted mostly of

aquatic insects, some amphibians, and only occasionally fish. Move-

James Clare Vanden Berge

ments from the nest were noted after 10 days; the first attempts to
fly, after 2; weeks.

Behavior patterns of young herons are varied. Those studied
included gagging, gular fluttering, vocalization, defecating activities,
and climbing.

The mortality rate in this study was high. Twenty-three of the
66 eggs were infertile, stolen or damaged and deserted. Forty-three
of the 56 young were found dead or missing from the nests. At least
one case of mammalian predation was observed. Other mortality factors
are discussed.

Samples of the associated flora were identified, and a list of
the associated fauna was kept.

Several tables, a map, and a graph are presented in the text.

A STUDY OF THE NESTING OF

THE GREEN HERON (PUTORIDES VIRESCEITS) In SOUTTZERN IvIICHIGAI‘I

 

By

James Clare vanden Berge

A THESIS
Submitted to
Michigan State University

in partial fulfillment of the requirements
for the degree of

LESTER OF SCIENCE

Department of Zoology

1960

Acknowledgements

The author wishes to express his appreciation to Dr. George J.
Wallace for his patient guidance of this study. I am also indebted
to the Department of Zoology at Michigan State University for the
use of the necessary field equipment, without which this study would
have been greatly impaired. My gratitude is also extended to Dr.
Max Hensley and Dr. John H. Beaman for their help with the manu-
script; to Dr. Roland Fisher for assisting in the identification of
the aquatic insects found in collected food material; to Mr. William
Horton for the use of the property on which the study colony was
located and for the use of the map; to my wife, Mildred, for typing
the manuscript in all its forms; and to all others who contributed

in various ways to this study.

Table of contents

Page

Acknowledgements oooooooooooooooeooo.ooooeo...oooooooooooo.oooooo il

LiSt Of tables, map, and graph 00000000000000.0000...0000000000... V

Introduction 000000000000000000000000000...00000000000000.0000... 1
Kethods Of Stfldy OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO00000000000 2

Relationships in the ("anus Butorides ............................
g Q ..___-‘.——

Distribution Of the Green Heron 00.000000770000000.0.90.00.00.00.

*4 \D \N

Arrival and departure dates in Kichigan .....................
Location and description of study colony ......................... 11
Height Of neStS oooooooeooooe00000000000000.ooooooooeeoooooeooeooo 15
Nesting trees o...0.00000coo00.0000000000.000OOOOOOOOOOOOOOOOOOOO 14
Nest structure 00......coo-o.ooeoooooooooo.00000000000000000000000 20
Eggs and egg-laying .............................................. 22
Incubation oeoooooooooooooooooooooooooooooooooooooooooeoooooooooo 25
Nestling period .................................................. 24

GI‘OWtho 000.00oooooooooooooooo00000000OOOOOOOOOOOOOOOOOOOOOOO 21+

Development oooooooooooooooooeoooooooooooooo00.000.000.000... 24

Feeding Of the young oooooooooooooooooooooooooeoooooooooooooo 25

rd

ledging 00000000000000.0000000000000000000.00.00.000.000000000000 51

Behavior of young Green Herons ,,..,,,,,,,..,...,,,,.,,.,,,,,,..,, 52

a ”f)
Gagging OOOOOOOOOOOOOOOOOOOO000.0.oooooooo0.0000000000000000. 9L

GUIHP fluttering .gggooo0.0000...to...0.000000000000000000000 52

vocalization .ggggooeooooeooooooooooooooooooooeoooooooooooooo 52
DGfeCBtiOD 00.000.000.000...0.000.000.cocoooooooooooooooooooo 52
Ffllling 00.000.000.000o00.000.000.000.0000000000000000000000 55

111

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Table of contents (cont'd)

Page
Post-juvenal migration 00.0000000000000000.000000000000000... 55

Mortality 00.000000000000000...0000000000 00.000000000000000000000 54
ASSOCiated vertebrate fauna 0000000000o.o00.000.OOOOOOOOOOOOOOOOOO 40
Associated flora 0000000000000...oooooooooooooooooooooOOQOOOoooOOo 44

Summary ooooooooooooooooooooooooooooooo..ooooooooooooooooooooooooo 47

Literature Cited 00.000000000000000.c00......OOOOOOOOOOOOOOOOOOOC. 50

iv

IQNQJ‘fl-U"

noon-co..-

Table

\OCDNIO‘sW-II'W

10
Map 1

Graph 1

List of tables, map, and graph

Page

Some arrival dates for Green Herons in Kichigan ..........
Last dates of Green Herons in Michigan ...................
Height of the nests in 1958...............................
Height of the nests in 1959 ..............................
Summary figures for height of the nests, 1958 and 1959 ...
Food of young Green Herons ...............................
Mortality, 1958 ..........................................
Hortality, 1959 ..........................................
Associated avifauna ......................................
Associated flora .........................................
Location of study colony .................................

Increase in weight (gms.) plotted against approximate .....

age in days 00.00000o.0000...o.0000000000000000000000000...

b

9

1o
16
18
19
50
58
59
1+1
45
12

Q9

Introduction

The Green Heron is the most abundant summer resident heron
in Michigan. However, there has been no detailed life history study
of this species published within the last 50 years.

Though the Green Heron is generally considered to be a
solitary nester, a small colony of breeding birds was found within
a pine stand on the border of a marsh in Barry County. This pro-
vided an opportunity not only to study the life history of this species,
but also to observe these herons in a nesting colony.

This study was carried out from July to August, 1958, and again
from April to July, 1959. It is hoped that this study provides
field data which can be used for comparison with similar life

history studies of this species.

Methods of Study

During this study, daily field trips were made to the heron
nesting colony except for a few weeks in the early part of the 1959
nesting season. Two nests were studied from blinds located on the
ground close to the nest trees. Daily records were kept on the progress
of these two nests, and in addition, a daily record was kept for
each of the other nestings for both seasons, regardless of their .
stages of development.

The heights of all but 2 of the 57 Green Heron nests found during
the 2 years were measured from the base of the tree by means of a
20-foot rope, marked off in inches and feet. Weights were attached
to the rope so that it could be suspended from the nest. A certain
amount of error in such measurements was thought to have been reduced
by the number of measurements taken.

The weights of the nestlings were determined by means of a
Pelouze Dietetic Scale, Model YG—500, fibesuring 500 grams by 1 gram
intervals. The birds were weighed on the ground beneath the nest up
until 10 days after hatching, after which taking weights became

impractical.

Relationships in the genus Butorides

The Green Heron (Butorides virescens) is perhaps the most

 

common of the summer resident herons in Michigan. It has also been
called the Little Green Heron, Green Bittern, "poke", "fly~up-the-
creek", "chalk—line", and "Skeow" (Bent, 1926), but the common name,
Green Heron, is listed in the most recent checklist (A. C. U.

Checklist of North American Birds, th Ed., 1957).

 

In North.America (not including Mexico or such off~shore islands
as the Bahamas, Bermuda, and the West Indies), the genus Butorides is
composed of a single species (virescens) which in turn is divisible

into 5 subspecies: virescens, frazari, and anthonvi. The original

 

generic name assigned to the Green Heron by Linnaeus (1758) was

Ardea; the present genus, Butorides, was described by Bonaparte (1855).
Recent investigations by Back (1956) and Moyerriecks (1958) have

disclosed new information as to the stability of the genus and its

evolutionary relationship to the other genera of herons. Bock re-

tains the genus Butorides in the Subfamily Ardeinae, the typical

herons, whereas Meyerriecks suggests a closer relationship to the

Subfamily Botaurinae, the bitterns, especially to the genus Ixobgy hus.

 

Meyerriecks further believes that Butorides is somewhat transitional

between the Botaurus-Ixobrychus complex and the more "advanced"

 

species of such genera as Ardea, Hydranassa, and others. His conclu-

 

 

sions were based primarily on behavioral characteristics. Both

authors, however, consider the genus Butorides as a stable taxon, but

admit that its members have interbred for some time, especially B. stria-

tus and virescens.

Distribution of the Green Heron

The most recent A. O. . Checklist (1957) sets the distribution-
al limits for the Green Heron from northern Colombia (Rio Baudo) and
Venezuela (Caracao), northward through Central America and the West
Indies, and over nearly all of the United States to southern Canada.
The range in Canada is principally from southern Ontario eastward to
southern New Brunswick. Green Herons breed over most of their range,
but winter chiefly from the United States southward. The eastern form
virescens is accidental in Greenland, Bermuda, and Surinam.

Two unusual winter records have been reported from Indiana:
at Indianapolis, January 5, 1916 (Wilson, cited in Bent, 1926) and
at Goshen, March 18, 1918 (Eby, cited in Bent, 1926). A sight record
10 miles north of Park Rapids, Hubbard County, Minnesota, early in
August (Audubon Field notes, 5, (5); October, 1949) is extremely far
north for the species. Bent (1926) states that this form according to
Loveland (1895) is a casual visitor as far west as Colorado.

The western form anthonyi occurs chiefly in Washington, Oregon,
and California during the breeding season and occasionally eastward to
Nevada and Utah. The southwestern form frazari is resident locally in
the southern half of Baja, California.

In Michigan the first authoritative listing of the eastern form,
virescens, was by Gibbs, 1879 (cited in wood, 1951). wood lists the

Green Heron as a common summer resident in the southern 5 tiers of

counties, locally northward to Chebovvan County". Barrows (1912)

U L.)

recorded a specimen collected May 2, 1898, in Kalkaska County and

5

another taken at the St. Mary‘s River in Chippewa County, A sight
record (Kneeland, 1859) at Keweenaw Point is considered doubtful
by Wood, although Barrows included it in his book.

A nesting record at Kud Lake, Sections 20 and 21, Grant Township,
Cheboygan County, on July 14, 19A1, is believed to be the northernmost
nesting record for the state (Root, 1941). Other nesting records at
Hess Lake, Newaygo County (Ford, 1922, cited in Wood, 1951), and at
Gladwin Refuge, Gladwin County (Dockham, 1954, cited in Wood, 1951),
indicate that the birds are able to nest successfully farther north
than Barrows' arbitrary "Grand Rapids east to Port Huron" limit.

ther northern sight records and collected specimens may well be
non-breeding birds, either adults or young wandering northward during
the post-breeding period, a trait not uncommon to the herons (Coffey,
1945). However, the abundance of nesting records for the southern
portion of the state seems to indicate a heavier concentration of

breeding birds there.

Arrival and departure dates in Michigan

The Green Heron arrives in Michigan during the period from mid-
April to early May, the heaviest migratory flights occurring about the
first of May. Early arrival dates include April 1, 1959, at Midland
(Kenaga, cited in Black, 1949) and April 5, 1955, 2 in Jackson County
(Wolcott, cited in Wickstrom, 1955). A record of a Green Heron reported
on March 19, 1904, is considered doubtful by Wood (1951). In Table 1
most of the arrival dates fall into the period from.April 20 to May 1.
This is in general agreement with other published references for
this latitude (Roberts, 1956; Forbush, 1959; Trautman, 1940).

The migration southward occurs during the period from mid-
September through the first part of October, with most of the herons
having left the state by October 15 (see Table 2). Late records include
October 24 in the Saginaw Bay area (Kenaga, 1956); October 26, 1955,

1 adult (2) at Three Rivers (Bryens, cited in Wickstrom, 1955), and
5 in Wayne County, November 5, 1905 (Swales, 1908).

Data collected durin this study agr e with these dates. My

8::
first record in 1959 was April 50, at Lake Lansing, and, for the nesting
colony, May 1 (although I was absent from the nesting colony during

the period April 27-May 1). My last record for the year Was September
22, 1959, at Knollcrest Farm, Grand Rapids. Data for the 1958 season
are incomplete.

The migratory flichts of Green Herons occur mainly at night

Q
L:

q 1 o “u _ u o -v
(Audubon, 1840; Griscom, 1925; neston, Cited in Howell, 1:92;

7

Cruickshank, 1942), and particularly during warm spring rains (Beyer
and Kopman, 1908). The speed of flight varies from 22 miles per hour
(Wood, 1955, cited in Heyerriecks, 1958) to 54 miles per hour (McLean,
1950, cited in Meyerriecks, 195°). Keyerriecks has a personal record
of 25 miles per hour.

Allen and Mangels (1940), in their study of the Black-crowned

Night Heron chticorax nvcticorax state that the "arrival dates
L; _.H J! ’

 

may be counted on regardless of weather conditions and apparently
irrespective of temperature, although winds from an unfavorable
quarter may retard migration". Weather conditions for most of the
week prior to the first sight record in the colony in 1959 were
generally unfavorable. Winds were cold and often quite strong,
mostly from the east-northeast. Skies were generally overcast and
frequent cold rains fell. These weather conditions may have had a
"slowin —down" effect on heron migration at least into the stud‘

5 a, 9

' t ”a 1 li””‘ th ‘h d't°- " b ,~ 11
area. Af er may , -53 e weat er con l tho ecame genera y

fairer and warmer.

Table 1 Some arrival dates for Green Herons in Michigan

County

Midland (Midland)
Jackson

Kalamazoo (Vicksburg)
Clinton (St. Johns)
Washtenaw (Ann Arbor)

Van Buren

Kalamazoo (Augusta)
Ingham (Haslett)

Ottawa (Allendale)
Tuscola

Bay (Saginaw Bay area)
Kalamazoo (Kalamazoo)
Ingham (Lake Lansing area)
Benzie

Isabella (Mt. Pleasant)
Ingham (East Lansing)
Wayne

Kuskegon (Muskegon)
Saginaw (Zilwaukee)
Ingham (Lake Lansing area)
Barry (CFOTked Lake area)

Erand Traverse (Traverse City)

April

10
11
15
14
17
18
19
21

21

24
24

26
26

28

\JJ
0

Month

Table 2 Last dates of Green Herons in Michigan

Count*

Oakland

Bay (Saginaw)

Van Buren (Paw Paw)
Calamazoo (Vicksburg)
Kent (Grand Rapids)
Muskegon (Muskegon)
Genesee

Kalamazoo

IIidland (,l-iidland)

St. Joseph (Three Rivers)
Saginaw (Zilwaukee)
Lapeer (Imlay City)
Cheboygan (Cheboygan)
Saginaw (Zilwaukee)
Washtenaw (Ann Arbor)
Ottawa

Macomb (St. Clair Beach)
Lapeer (Imlay City)

Wayne

St. Joseph (Three Rivers)

Wayn e

10

September

17
18
20
21
22
25
20

I

50

Month

 

October

COO\\J]

‘O

10
10
15
18
18
21
26

November

Location and description of study colony

Observations were made from July 4 to August 22, 1958, and
again from April 18 to July 17, 1959, except for temporary absences.
The study colony of nests was found in a small stand of pine trees
(Pinus sp.) located 10 North by 100 West in Section 12, Prairieville
Township, Barry County, Michigan.

The stand borders what is now a marsh succession following the
drying of a formerly extensive post-glacial lake. The lake remains in
two relatively isolated bodies of water, the Upper and Lower Crooked
Lakes, connected by way of an extensive marsh (the Bay on Map 1).

A peninsula of pines projects in a northeast by southwest direction

into the marsh itself. The hatched area on the map has been land—

scaped and planted in cooperation with the Farm Game Habitat Improve-
ment Project of the Game Division of the Michigan Department of Conserva-
tion.

Fifteen or 20 years ago, some 2000 trees, mostly Red Pine (Pinus
Efginosa), White Pine (3. strobus), and Austrian Pine (P. nipra) were
planted on a 2é-5 acre plot. Rising water levels destroyed many of the
trees along the edge of the stand during the first few years. The
owner also permitted local and scattered removal of trees for use at

Christmas time. Natural succession in the area, following these two

factors, has kept the stand relatively isolated today.

11

Map 1 Location of study colony

upper CrookQJ Lake

    

 

 

Hovf'on's
3!
S
w (A) N
"- I o Ila
23:43 6[ in”: w
“a / [I U
. T / ”D s
g u P Per
o- (VookOJ
Lake

 

C POP (and

Scale (M. = 40 5"on
w,llgah How-+0.,

 

USOJ by PQVW‘55l0h or 7“! OWKQV,

12

Height of nests

Within this pine stand, 28 Green Heron nests were located during
he 1958 season. Each was labelled and measured for height from the

base of the tree. Only 14 of these nests still contained eggs or
young when I began the study on July 4 (Table 7); however, the
other 14 nests were assumed to have been used that season since
shells of heron eggs were found beneath each tree. During the 1959
season, only 9 Green Heron nests were found, but 2 of these were
intensively studied. These 9 nests were labelled and recorded
in the same manner as the 1958 nests (Table 8).

In 1958, the average height of the 28 nests was 11.7 feet with
a standard deviation from the mean of 1.4 feet. In 1959 the measure-
ments were 11.7 feet for the average height with a standard deviation
of 0.9 feet. hough the average height was the same for both seasons,
there was a wider deviation from this mean during 1958.

The average height of the nests in the Red and Austrian Pine was
the same as that in the White Pine, 11.8 feet. However, there was a
significant difference in the standard deviations (Table 5). The 2 nests
not in pines were 9.2 feet and 12.5 feet. In general, extremes in the
height of the nests showed some difference, as much as 5.5 feet be-

tween Nest #11-58 and Heat #18-58.

15

Nesting trees

For this study the percentage of nests in Red and Austrian Pine was
56.8; in White Pine, 55.1 and in other trees and shrubs, 8.1. For the
2 seasons, this percentage showed that during 1958, 64.5 of the nests
were in Red and Austrian Pine; 28.6 in White Pine, and 7.1 in other
trees and shrubs. In 1959, these percentages were 55.5, 55.6 and 11.1
for the 5 groups respectively. From these data, it can be seen that
nests were found 21.7%:more in Red and Austrian Pine than in White
Pine and that a very small percentage (8.1) were found in other
trees and shrubs. This might be expected since this was a pine stand.

Also in this study 2 nestings occurred in the same tree or shrub
and, in one case, at the same height (Nest #1-58 and Nest #1-59).
Heat-#7-59, in the same hawthorne (Crataegus macrosperma) as Nest
$10—58, was not measured for height.

The published literature relating to the species of trees and
shrubs in which Green Heron nests are constructed and the height at
which they are found is rather extensive. Bent (1926) cites the following
types of trees which have been used: roots of mangroves (Haynard,
1896); pitch pine, grey birch, red oak, cedars, sassafras, and
hickories (Townsend, 1920). Mrs. hheelock (1906), in her life history
study of the Green Heron, found 4 nests in evergreens, 1 in an apple
tree of an orchard, and 1 in a small cottonwood. Root (1941) found

(1

a nest in a Black spruce Pi.oa acriana while Ramp 1951 studied
A , -L /

 

a small colony of Green Herons in buttonbush (Cephalanthus occidentalis).

 

Several other authors record nesti gs in these types of vegetation and

14

in other types as well (Barrows, 1912; Roberts, 1956; Forbush, 1959;
Trautman, 1940). Apparently any tree or shrub which can support the
bulky nest can be used as a nest tree.

The height of the nest may also vary. Bent (1926) states that
the nest may be found on the ground, in low bushes, and 10 to 20
feet high in trees. Rapp (1951) studied nests from 8 to 10 feet
high in buttonbush. Cooley (1942) studied a nest in a willow tree
only 57 inches above the water. Maximum heights for the nests are

50 feet in a maple tree in an upland pasture (Roberts, 1956) and

I

h

50 feet in a willow tree (probably subspecies anthgyi; Huey, 1915,
cited in Bent, 1926). In general, the average height of the nests in
this study agree with those published in the literature.

Though generally considered to be solitary nesters, Green
Herons sometimes nest in small colonies. One colony studied by
Rapp (1951) contained several nests. Townsend (1920) notes that 20-50
pairs nested together in pitch pine some 20 feet from the ground, and
also some 20 nests in cedars, sassafras, and hickories, from 5-20
feet in height. Pearson (1925) reported that 6—8 pairs sometimes
nest together. Other Green Herons have been known to nest in associa-

tion with colonies of Great Blue Herons (Ardea herodias) and Black-

 

Crowned Night Herons (Nickell, 1958, pers. comm.; Bent, 1926).
Perhaps, as Meyerriecks (1958) states, "there is a tendency toward
colonial nestings in favorable habitats“.

The data relating to personal observations and records for the

nestings are included in the following tables (Tables 5—5).

Table 5 Height of the nests in 1958

 

 

 

16

Nest Number Species of Tree (Inch;:)Q2;eet)
1-53 White Pine 127.5 10.6
2-58 Red or Austrian Pine 150.0 12.5
5_/3 Red or Austrian Pine 158-5 11.5
4-58 Red or Austrian Pine 156.0 15.0
5—58 Red or Austrian Pine 156.5 11.4
5_e3 White Pine 108-0 9.0
7-58 Red or Austrian Pine 140.0 11.7
8-58 Red or Austrian Pine 159.0 15,5
9-58 Red or Austrian Pine 141.0 11.8

10-58 Hawthorne 110-0 9.2
11-58 Red or Austrian Pine 172.0 14.5
12-58 Red or Austrian Pine 144.0 12.0
15-58 Red or Austrian Pine 125.0 10.5
14—58 Red or Austrian Pine 152.5 11.0
15—50 Red or Austrian Pine 150.5 10.9
16-58 Red or Austrian Pine 149.0 12.4
17-58 Boxelder 150.0 12.5
18—58 Red or Austrian Pine 106.0 8.8
19-58 Red or Austrian Pine 140.0 11.7
20-58 Red or Austrian Pine 152.0 11.0
21-53 Red or Austrian Pine 150.0 12.5
22-58 White Pine 157.0 11.4

Table 5 Height of the nests in 1958 (oont'd)

 

 

 

Height
Nest Humber Species of Tree (Inches) (Feet)
25-58 white Pine 155.0 12.9
24—58 White Pine 165.0 15.8
25-58 Red or Austrian Pine 156.0 15.0
26—58 “hits Pine 168.0 14.0
27-53 Hhite Pine 156.0 11.5
28-58 White Pine 152.0 11.0
Average height of all nests 'X 3 140.9 11.7
Standard deviation from the mean .g = 16.4 1.4

17

Table 4 Height of the nests in 1959

 

 

Nest Tumber Species of Tree

1-59 White Pine

2-59 White Pine

5-59 Red or Austrian Pine
4-59 Red or Austrian Pine
5-59 Red or Austrian Pine
6—59 White Pine

7‘59 Large-seeded Hawthorne
8-59 fhite Pine

9-59 White Pine

Average height of all nests

Standard deviation from the mean

18

7? O 1
height

(Inches)_(Feet)

125.0
143.0

144.0

10.4

0.9

Table 5 Summary figures for height of the nests, 1958 and 1959

 

 

 

 

19

Species of No. of “fiiof Average Height Standard Deviation

Year Tree Iests Nests Inches Feet Inches Feet

1958 Red and 18 64.5 142.0 11.8 14.9 1.2
Austrian Pine

1958 White Pine 8 28.6 141.0 11.8 20.5 1.7

1959 Red and 5 55.5 158.7 11.6 6.8 0.6
Austrian Pine

1959 White Pine 5 5.6 142.5 11.9 15.2 1.2

TOTALS Red and 21 61.8 141.5 11.8 14.0 1.2
Austrian Pine

White Pine 15 58.2 141.5 11.8 17.6 1.5

Nest structure

The nest of the Green Heron is an unlined platform consisting of

Ho

dead sticks of various shapes and sizes. A shallaw depression 3
usually formed at the center of the neat, but this probably results
from the weight of the adult bird as it sits in the nest. The sticas
are somewhat interlaced by the adults during the period of nest con-
struction (Meyerriecks, 1958), but even when completed, the nest is
still quite porous.

From observations of completed nest construction, I have noted
that, in general, the nests placed in the main whorl of branches are
larger and bulkier than those placed out from the trunk. The latter
are usually constructed at the nodes of the branches where smaller
needle-bearing branches diverge. Perhaps the smaller amount of space
available prevents the formation of a larger nest in these cases.

The average diameter of the nests was about 8 inches; the total
diameter was more difficult to determine because of the protruding
sticks. Except for a few sticks which protruded further from the
nest, the greatest diameter was some 12 inches.

The nests were not only quite loosely constructed, but also an
obvious lack of cleanliness was evident particularly after the young
hatched. Feces accumulated on the nest sticks, the bark of the tree,
and the surface of the ground. No attempt at cleanliness on the part
of the adults or young was seen, and flies and other insects were seen

around the nests a good deal of the time. Perhaps, as Wheelock (1906)

20

has said, "But herons are inured to hardships from their birth,

it seems, for no lining of any sort was found in any of the nests,

the young reposing on the coarse twigs in the midst of indescribable un-

cleanness."
No data are available in this study concerning the elaborate stick—
DJ.‘

presentation ceremony, an aspect oi the courtship behavior discussed

in meticulous detail by Keverriecks (1958).

v
I:

21

Clutch sizes in the present study are listed in Tables 7 and 8
in the section dealing with mortality. The average clutch was 5.5 eggs,
with a variation from 2-5. This agrees with the clutch size as de-
termined from Rapp's (1951) data (although he assumes the possibility
of a second brood in his study), but is somewhat lower than other
clutch sizes recorded in the literature (Bent, 1926; Trautman, 1940,
and Wickstrom, 1950).

PA

The average size 0 20 eggs in this study was 59.1 mm. x 29.9 mm.,
with extremes of 45.0 mm. x 29.0 mm. and 58.0 mm. x 28.0 mm. These
data agree with measurements recorded in the literature (Gentry, 1882,
and Bent, 1926).

In my only record of the time of laying, the third egg of Nest

fits—59 was laid between 12:00 and 4:00 PI-‘I, May 29, 1959.

F0

Incubation

Burns (1915) listed the incubation period of the Green Heron as 17
days. Cooley (1942) determined the incubation period of 4 eggs to be
20 days. In the present study, the average length of the incubation
period for 10 eggs was 25 days. The closest determination was that for
the third egg in Nest #6-59 (see above) which was laid on the afternoon
of May 29, 1959, and was already hatched (less than 1 day old) on the
morning of June 22, 1959 (a period of 25 days).

The incubation period for 9 other eggs was determined from the

g and hatching. The data in Meyerriecks

O

approximate dates of layin
(1958), indicated that the average number of days for incubation was
likewise 25 days.

In this study it was impossible to determine the relative length
of time during which each adult was in attendance or absent from the
nest since the sexes were indistinguishable and were not marked.
Meyerriecks (1958) recorded that the male incubates mostly throughout
the mid-day and mid—night hours, while the female sits during the
early morning and late evening hours. Kendeigh (1952) recorded that
both sexes incubate alternately at intervals of 2-6 hours during the
day and that the female incubates during the night.

Kendeigh (op. cit.) mentions an elaborate replacement ceremony,
although Meyerriecks maintains that this ceremony disappears as in—
cuhation progresses. I did not see any replacement ceremony during my
observations of incubating bir s, but rather a simple exchange of the

tro adult birds at the nest.
25

Nestling period

9E2EEE“Th° weights of the young herons increase at a regular
rate during the first 10 days after hatching (see graph). After
this the young are able to move out of the nest and cannot readily
be handled and weighed. All data pertaining to the weights of the
young were recorded at approximately the same time of day. The 4
nestlings in Nest #6-59 were marked with red decorative enamel on the
feet or legs so that the weight of each could be followed individually.
The 2 young in Nest f4-59 could be distinguished by their respective
stages of development. The data obtained for the 4 young in Nest #6-59
were calculated by comparison with the other nestlings since the
exact ages were not known.

Wheelock (1906) recorded that the increase in weight for young
green herons was 1/2 oz. per day (14.2 gms.) and that the average
weight at the end of 7 days was 5 5/4 oz. (96.5gms.). No additional
data were given. The 4 young in Nest fi6-59 had an average gain in
weight per day of 8~10 gms. and at the end of 7 days had an average
weight of 84 gms.

Development--The young develop rapidly after hatching. Within

 

2-5 days they are already sitting up in the nest, maintaining their
position by gripping the nest sticks with their strong toes. If they
are handled, the young flex their toes, grabbing at the nest and often
picking up loose twigs from the nest which they continue to hold even
when they are being weighed.

t the end of 6-7 days of development the young are actively

24

moving about on the flat nest. At this time the youngest nestlings
are subject to some abuse by the older ones. Often in looking into
the nest, I have seen only 5 of the A young in the nest, with the #th
one (usually the youngest or smallest) concealed beneath the others.

he typical resting position of the nestlings resembles some-
what a “bittern stance". Their long necks are held vertically, the
bill is projected at an angle, and the eyes are directed downward
toward the ground. The body is often twitching nervously, probably
because of a general alarm in the young. The snapping of the tail,
a behavioral aspect of the adult birds associated with ngeneral ex-
citabilityn (Meyerriecks, 1958), is also a part of this peculiar
habit.

After 10 days the young are able to leave the nest and to perch
along the branches nearby. Except for the crest feathers which are
just beginning to show, the plumage in the young is well developed
by this time. Traces of the grey down still cling to the feathers.
The bills, feet, and legs are long and very strong. After 10 days,
the young become more independent of the nest and soon move away
from it into other trees.

Feeding 32.323'zggng——The young are fed by regurgitation.
Apparently the food material is regurgitated into the nest during
the first days of development. My field notes record the following
incident involving a less than one~day—old nestling (Nest #4-59):

"In the nest were an unidentified minnow about 1 1/2 in.
long and a small frog (Acris crepitans). As I prodded

the food with a pencil, the nestling seized the minnow and

began to manipulate it until the whole fish could be swallowed

head—first. The minnow was almost too large for the young

bird to swallow and the meal was not down for about 5

minutes. During this time the eyes were closed and the

head and neck were lifled and then dropped again as the
bird struggled with the food. . . . ."

25

 

The feeding activity~begins with the first egg hatched. A single
unhatched egg was still in this nest.

The young peep almost continuously from the time of hatching.
Within 5 days a rapid clicking by the young can be heard in addition
to the peeping. Both sounds may be associated with feeding because
the sounds continue until after the young have been fed.

The young, when they are able to move about in the nest, usually
face in the direction of an approaching adult. This approach of the
adult bird is accompanied by a series of low 'cucks" which stimulates
a louder peeping and clicking by the young. A good deal of gaping also
occurs. The young face the approaching adult and open their bills
exposing the large mouth cavity. This is not the same as gagging (see
section on behavior of young Green Herons) because no attempt is made
to regurgitate food material.

As soon as the adult reaches the nest, the young seize the bill
crosswise and begin to stroke it. This seizing of the bill probably
acts as a "releaser stimulusn which causes the regurgitation of the
food material (Lowe, 1954). Both the young and the adult engage in
an active struggle which involves a twisting and turning of their heads
and bills. This struggle becomes more evident as the young develop.

Not all of the regurgitated food material is swallowed by a
young bird. Some of it is picked up by the adult and either swallowed
or thrown out of the nest.. The young birds also pick at each other
following each feeding, although no second regurgitation by the
young themselves was seen.

Feedings occur in the branches after the young have left the nest.
The young must then maintain their balance while being fed. A

peculiar habit of "dancing with the wings arched high over the back

26

also occurs just prior to feeding at this stage of development. A
captive bird exhibited this same behavior as it begged for food.

No data are available in this study as to the sequence of feeding
by each adult bird. Most of the feedings took place during the early
morning and early evening. Wheelock (1906) recorded that the young
were fed only in the early morning and late afternoons, especially
from 4:00-6:00 AM and 5:00-7:00 PM. In this study no feedings were
observed after 7:00 PM., although there was a feeding at 6:50 PM,
after which the young returned to the nest from a branch and quietly
remained there.

The types of food fed to the young were determined from regurgitated
food in the nest, from regurgitations of the young, and by means of
stomach examinations of dead young. No attempt was made to correlate
the types of food offered with the age of the young nor with the
environmental conditions for that particular feeding period. Whee-
lock (1906) has an elaborate arrangement of the type of food fed to
the young compared to the environmental conditions for that perticue fl
lar day (for example, crayfish, minnows, snails and slugs on cloudy
morning). Cooley (1942) was able to show that certain types of food
were regurgitated for the young depending on their ages. Most of
this food consisted of fish, which formed little of the food material
in this study.

A list of the food material collected and identified is
included in Table 6. The young were fed mostly on aquatic insects,

amphibians (mostly Acris crepitans and Rana p

 

 

piens which were
abundant nearby), and occasionally fish. An interesting point here is

that large schools of bowfin (Ania calva) were planted in the lake

 

by the Hastings Fish Hatchery as part of a controlled experiment in

A'

27

laLe production. This species was found in several examinations.
Cottam and Uhler (1957) have shown quite conclusively that the
food of Green Herons consists mostly of aquatic insects, particularly
dragonfly nymphs, predacious diving beetle larvae, and large water
bugs of the genus Belostoma. Other authors also record large numbers

of aquatic insects in stomach examinations (Gentry, 1882; Bent, 1926;

Roberts, 1956; Trautman, 1940).

28

Graph 1 Increase in weight (gms.) plotted against approximate age
in davs

3‘33?

8‘

15‘

17.09.39. m “9'943‘ ’* Eran;
u m
o 0

t“

 

1 z, 3 4 5 . 7 a 9 to
Approxlmad'e ‘39 M 04"“

29

Table 6 Food of young Green Herons

June 11, 1959, iest fi4—59, a young heron (5 days old)
regurgitated a 4 gm. mass of par-
tially digested food, identified as
the larva of a dytiscid beetle.

June 24, 1959, Nest #6-59, the regurgitated food

material consisted of two small frogs
(Loris crepitans)

 

June 25, 1959, Nest #6-59, mostly frog remains in
food material

June 26, 1959, the following were identified in food
material which had been collected and
preserved earlier:

dytiscid beetle larvae~2

belostomatids

Acris crepitans-5

remains of others

unidentified frogoremains

bowfin—7 and remains of more

centrarchids (Lepomisipp.)—2
Nest §5-59, tadpoles (just showing legs)

 

July 10, 1959, identified food material:
dytiscid beetle larvae—2
belostomatids-l
cuculionids~121
odontid naiads-2 .
hellgrammite-l
elytra of chrysemelid beetle
(Donacia.§p.)

\c‘i

Pledging

The young become more independent of the nest after they once
venture out of it (about 10 days after hatching . By 2 weeks of age,
they are able to jump from branch to branch in the nest tree. They
make use of their head, neck, bill, and wings for maintaining their
balance when landing in a new position. The young do not return to
the nest after they are able to move from branch to branch.

The first attempts at flying are made at about 2% weeks of age.
The first flights are generally just a few feet, usually the distance
between two limbs of the tree. At this time the young were difficult
to follow except by the movement of the branches as they jumped and/or
flew from one to another.

A young heron from Nest %5—59 was seen in a tree about 54' from
the nest at 22 days of age. Although the bird was completely feathered
(except for traces of the grey down on the crest) and was able to fly
for several yards, it was still being fed by the adult birds. Burns
(1921) records that fledging takes 4-5 weeks. This young bird was

then probably near the end of the fledging period.

$1

Behavior of young Green Herons

Gagging—-The young nestlingsoften appear to gag when an intruder

is present. The mandibles are opened very wide, and the sides of the
mouth are stretched exposing the mouth cavity which then appears very
large. In closing the mouth again, the young extend the head forward.
This sequence of events suggests that the young are choking or "gagging".

Sometimes this gagging results in the regurgitation of food material.

Gular fluttering--On very warm, sunny afternoons the young show a

 

fluttering of the gular region. This is probably a means of reducing
the body temperature since it is often seen when the young are sitting
in direct sunlight. A captive bird also drooped its wings while
exhibiting this behavior. Similar gular fluttering has been reported

in the Lesser Nighthawk (Chordeiles acutipennis) in Texas (CowlBs and

 

Dawson, 1951) and in the Poor-will (Phalaenoptilus nuttallii) in Calif-

 

ornia (Brauner, 1952).

Vocalization--The peeping and clicking by young herons has already

 

been discussed as an aspect of feeding. When the young are about 7
days old and are actively moving about the nest, they wil1 give a loud,
raspy alarm note ("cfi§ck“) when approached by an intruder. This call

-

is accompanied by striking movements of the bill and head. LO other

-’——-I

calls by the young were heard.

Defecation-~The young defecate directly into the nest before they

 

are able to move about. iowever, as they develop and become more

active, the young will defecate at the rim of the nest.

52

The defected material is a white fluid which is voided from the body
while the young assume a squatting position. This acoumulates on the
nest sticks, the tree, and over the ground beneath the nest. The
material has a very strong fishy odor and, as it accumulates, the whole
nest area takes on this odor.

Fallinc--The young herons have some difficulty in moving abou
the nest and the branches. Several times during this study young
herons were seen to lose their balance and fall several feet to a lower
limb or occasionally to the ground.

However, as soon as the young bird regains its balance, it will
begin to climb back to the nest. This is accomplished by placing the
bill over a branch and then using the wings for climbing. On at
least two occasions young were seen climbing several feet up into a
tree. One young (Zest 523-58) was thought to have returned to the
nest by itself, presumably having climbed from the ground up to the
nest (11').

The adult Green Heron apparently does not desert a young bird
when it has fallen from the nest. One nestling was found several
yards from the nest perched about 6' up among the branches of a willow.
The adult repeatedly flew low into this tree, apparently feeding the
young bird.

Post—juvenal migration-~Coffey (1945) discusses the dispersal of

 

young herons following the nesting period. Lowe (l95h) states that this
dispersal in all directions (often northward) is to find good living
conditions for the remainder of the season. He family groups or

groups of many young togethen suggesting post-juvenal migration,

were seen during this ptrticular study.

Mortality

Perhaps the most significant aspect of this study was the very
high mortality rate incident at the nesting colony. During the 1958
study, 12 of the 14 nests under observation failed completely, while
in 1959, 7 of the 9 nests failed. This destruction occurred both to
the eggs and to the young.

In 1958, Id of the 56 eggs (44.4%), and in 1959, 7 of the 50
eggs (25.5%) wire either infertile (2), stolen (14), or damaged and
deserted (7). This represents a total of 54.8% (25 of 66eggs).
Mammal predation of eggs was recorded in one instance. On July 12,
1

iudsonicus)

/

1058, an adult heron chased a red squirrel (Ta.iasciurus

 

from Nest fi4-55. Subsequent investigation indicated that 5 of the 4
esgs were damaged (the shells were pierced), and 2 days later, July 14,

the remaining egg was missing. Although this type of egg destruction
was seen but once, other losses were probably due at least in part
to predation by the squirrels.

As can be seen from Table 9, several avian predators were seen in

the area immediately surrounding the colony. Among those which might

have stolen or destroyed eggs are the Common Crow (Corvus brachyrhynchos),

 

Blue Jay (Cyanocitta cristata), and Common Grackle (Quiscalus guiscula).

 

 

The Brown-headed Cowbird (Yolothrus ater) and the Red-winged Blackbird

 

(Agelaius_phoeniceus) might possibly take an egg.

 

Lowe (1954) states that the Hooded Crow (Corvus_gornix) and the

 

Carrion Crow (Corvus corone) take heron eggs and young and that this

 

51+

may have considerable effect on a heron population. On the other hand,

he notes that magpies (Pica pica) and jays (Garrulus slandarius) often
y‘ m A

 

nest in the same trees as herons and apparently have little or no
effect on heron populations. Wheelock (1906) maintained that Common

31

Grackles served as watchmen", warning at the approach of other predators,

but only occasionally stealing an egg themselves. Crows, hawks, and
vultures (Audubon, 1840, cited in Bent, 1926; Baker, 1940; Provost,

1947; and Meyerriecks,l958), along with blackbirds and Forster's Terns

(Sterna forsteri) (Provost, 1947) have been mentioned also as predators

 

on heron colonies.

In addition to the high mortality to the eggs, the loss of young
is also significant. 0f the 55 young found in the colony during 1958,
some 28 (80%) were found dead while only 7 (20$) could have been
fledged successfully. During 1959, 15 of the 21 young (71.4%) were
found dead; 6 (28.6%) were probably fledged. Combined, these totals
show that 76.8% of the young were found dead or missing from the nests
and 25.2% were fledged.

The manner in which some of the young were killed seemed to
indicate hat larger avian and mammalian predators were entering the
colony although none except the red squirrel was actually seen. Several
young were partially or completely decapitated (owls?), eviscerated, or
mutilated in some other way. The proximity of a Cooper's Hawk

(Accipiter cooperii), nesting within the pine stand, apparently did not

 

affect this high mortality because repeated checks of the hawk nest did
not yield any evidence of heron remains. Lowe (1954) mentions that
peregrines nested in 8 out of 18 heronries in the state forests of

East Prussia in an apparent state of neutrality, although he does not

suggest complete immunity within the same area. Provost (1946) lists

‘ 55

the mink (Mustela vison) as a mammalian predator on herons while other

 

authors list raccoon (Procyon lotor) (Audubon, 1840, cited in Bent, 1926;

 

Baker, 1940) or possibly opossum (Didelphis Virginians) (Baker, 1940).

 

Finally, weather factors may have played a role. 0n the night of
July 14, 1958, a severe electrical storm swept the colony and in the
morning, 5 young were found dead (Nest #9-58). However, the fact that
some of these young were again badly mutilated might suggest death by
some predator(s) rather than by weather factors. Wheelock (1906)
reported the death of many young birds following such a severe storm.
Lowe (1954) also states that bad weather is a principal factor affecting
nestling mortality.

Other than the data already cited little can be added to explain
the very high mortality rate in this study, ,Lowe (1954) has dealt with
this aspect in his iife history study of the Common Grey Heron (Ardea
cinerea) and some of his conclusions are worthy of mention. The two
main factors responsible for a decline in heron populations in his
study were exceptionally severe winters and man. Citing Alexander,
Lowe states that the "decrease in the number of breeding pairs is
largely the result of the prevailing lowest temperature of the pre-
ceding winter, and as a rather high percentage of victims are young
birds, the effect on the heronries is noticeable for the following two
seasons (p. 682)." Perhaps the winter season of 1958-1959 took an
exceptional toll of potential breeders. If this were the case then
the lower number of nesting birds during 1959 would be expected.

The herons as a group have been protected by the Federal Migratofip
Bird Law (1915) for many years. In Europe, the herons are protected
locally, but many herons, particularly the unwary young birds, are shot
in the trout angling counties. This factor is probably not important

H 1"

in Michigan, since the Green Heron is not considered to be primarily
a fish eater (Cottam and Uhler, 1957).

There are no known epidemic diseases affecting herons; however,
Lowe suggests possible infestation of intestinal trematodes in young
herons, probably from the food which is eaten.

Competition with other nestlings for food and space in the nest
may have an effect on the mortality rate of nestlings. The younger
and weaker nestlings may die from hunger and exhaustion in competing
with the others for the attention of the adults. The greatest losses
apparently occur during the earliest days; then, if the young survive

to the third week of development, another rise in the mortality

rate may occur. This latter rise occurs at about the time of active

movement of the ounw about the nest area. At this time environmental
t- 2

factors, particularly storms and high winds, may have a decimating

effect.

 

mumps HH momma m ON 5 00 mm Hm Hmpoe
eons muses H muses m as m OOH e s mmumm
ewes ecsom made» O O OOH m m mmcqm
name cease muses o o 004 s s mmuom
ewes ecsom meson O O OOH d 4 mmIOH
same eases edge» «0 o OOH m m wmuma
MCHmmHS mmmm O O O O 4 wmldH
mchmHE mmmm O O O O J mmImH
was maasamucH a
mwchmHE meson H O O Om H N mmIHH
mason m OOH m OOH m m mmIOH
same eesou made» 0 o 00H m m mmuo
Hmaastm pea an
emmoapmme mmme O O O O 4 mmaq
maHmmHE mcdox m masom H mm H OOH d d mmum
vamp vasom made» O O OOH d d mmlw
Umpammme mmmm .O O Og O m mmIH
emmemau page samemae pass emsopse page canons;
venous: mmmm venous: mmMm UHmH mmmo awn» mmmm UHwH mmwe .oc
Hstmmooemca Hstmmoosm mo m mo .02 we a mo .0: mo .02 pmmz
mmaH CH mmeoosm mCHpmmz b mHnwe

58

AmmOH

 

s OmOHV

mH m OH 0 00 On mm mHspoH

; AmmOHv

mamas a mamas m smmmH pm a pmcmH as m smsmH as H» mm Hm mHmaoe

wCHmmHE ammo O O O O m mm!»

OehOApmmO mmm O O O O H mmlm
mHHsamCeH was H

memes mecca m o 0 mu m s Owns

ease eases H H pmmmH as am smmmH as H pmmmH pm OOH s s Om-O

same muses H H pmme as mm smsmH as H pmmmH as OOH s s Om-m
MCHmmHE mme

H eCm MCsoh m O 0 mu m d amid

Osmospmme same O O O O m Omum
Omen thmECmeCQ

mmchmHe mazes O O OOH a m Om-m
pmmC CH mme H

mmCsoh ewes m O O mb m 4 mth

emmemHC swap samemHC pans sweepsa uses emeopmn
. Omnopms mmmm venous: mmmm OHmH mmmm asap mmme OHOH mmmm .oc
HsmOmmoosmC: Hstmeoozm mo m mo .02 mo R mo .02 . mo .02 pmoz
0mmH CH mmeoosm MCHummz m mHnt

59

Associated vertebrate fauna

Several species of birds were seen within the pine stand or
flying about in the open marsh near the stand. Some of these were
seen before the herons arrived; others arrived during the nesting
season, and a few were present during the whole study, particularly

Song Sparrows (Nelospiza melodia). A complete list of all the birds

 

seen or heard in the area (approximately 640 square rods centered
around the colony) is given in Table 9.
The most common species was the Song Sparrow, but Black-capped

Chickadees (Parus atricepillus), Rufous—sided Towhees (Pipilo

 

erythrophthalmus) and Catbirds (Dumetella carolinensis) were seen and

 

 

heard daily. Of those which were seen overhead, flying between the

lakes, the most common was the Black Tern (Chlidonias niger).

 

A few species were known to have nested within or around the
colony. These are indicated by an asterisk in Table 9. Nesting
success for some species is known, and this has been included.

The four non-avian species included two reptiles and two wild

mammals. These four are a Midland Painted Turtle (Chrysemys picta

 

marginata), a snake (Thamnophis sp.), a muskrat (Ondatra zibethica),

 

 

and red squirrels.

4O

fl’I

Infill!

*(7)

Table 9 Associated avifauna

Great Blue Heron, Ardea herodias

 

American Bittern, Botaurus lentiginosus

 

Canada Goose, Branta canadensis

 

iallard, Anas platyrhynchos

 

Black Duck, Anas rubripes

 

Blue-winged Teal, Anas discors

 

Lesser Scaup, Aythya affinis

 

Common Merganser, Nergus merganser

 

Eastern Turkey Vulture, Cathartes aura

 

Cooper's Hawk, Accipiter cooperii

 

Red-tailed Hawk, Buteo jamaicensis

 

Marsh Hawk, Circus gyaneus

 

Killdeer, Charadrius vociferus

 

Spotted Sandpiper, Actitis macularia

 

Herring Gull, Last-as argentatus

 

Ring-billed Gull, Larus delawarensis

 

Black Tern, Chlidonias niger

 

Mourning Dove, Zenaidura macroura

 

Yellow-billed Cuckoo, Coccyzus_americanus

 

Belted Kingfisher, Hegaceryle alcyon

 

Yellow-shafted Flicker Cola tes auratus
: P _

 

Red-bellied Woodpecker, Centurus carolinus

 

Hairy Woodpecker, Dendrocopos villosus

 

41 .

Table 9 Associated avifauna (cont'd)

* Downy Woodpecker, Dendrocopos pubescens

 

** Eastern Kingbird, Tyrannus tyrannus

 

Great Crested Flycatcher, Myiarchus crinitus

 

Eastern Phoebe, Sayornis phoebe

 

Traill's Flycatcher, Empidonax traillii

 

Eastern Wood Pewee, Contopus virens

 

* Tree Swallow, Iridoprocne bicolor

 

 

Rough-winged Swallow, Stelgidopteryx ruficollis

Blue Jay, Cyanocitta cristata

 

* Common Crow, Corvus brachyrhynchos

 

Black-capped Chickadee, Parus atricapillus

 

Tufted Titmouse, Parus bicolor

 

* Catbird, Dumetella carolinensia

 

Brown Thrasher, Toxostoma rufum

 

Robin, Turdus migratorius

 

Cedar Waxwing, Bombycilla cedrorum

 

Solitary Vireo, Vireo selitarius

 

Warbling Vireo, Vireo gilvus

 

Yellow Warbler, Dendroica pgtechia

 

Myrtle Warbler, Dendroica coronata

 

** Yellow-throat, Geothlypis trichas

 

Eastern Meadowlark, Sturnella magna

 

Red-winged Blackbird, Agelaiusgphoeniceus

 

Baltimore Oriole, Icterus galbula

 

Common Grackle, Quiscalus quiscula

 

** Brown-headed Cowbird, Molothrus ater

 

l

42

Table 9 Associated avifauna (cont'd)

Cardinal, Richmondena cardinalis

 

American Goldfinch,_§pinus tristis

 

Rufous—sided Towhee, Pipilo erythrophthalmus

Field Sparrow,_§pizella pusilla

 

White-throated Sparrow, Zonotrichia albicollis

 

** Song Sparrow, Helospiza melodia

 

* Known to have nested around the colony.
** Known to have nested, but unsuccessfully. (The Brown-headed
Cowbird parasitized the nest 02 the Yellow-throat.)
*** Known to have nested successfully.

45

Associated flora

The dominant vegetation within the colony was a mixture of pine
(see Tables 5-5) plus a few other trees and shrubs. In those areas
in which the pines had been cleared, common weeds had grown in a
succession stage. Beneath the pines, however, there was very little
vegetation and most of this was of a species of bramble (Rubus sp.).

Scattered clumps of stsghorn sumac (Rhus typhina) and dwarf

 

sumac (Rhus copallina) had developed among the dominant vegetation.

 

Grape vines (Vitis sp.) were entangled in the pine trees in two
areas of the stand.

The border vegetation consisted mostly of buttonbush (Cephalanthus

 

occidentalis) and common cat-tail (Typha latifolia) with various

 

 

grasses and weeds on the drier areas near the pine stand. He nests
of the Green Heron were found in this area, although buttonbush is
often used for the nest (Rapp, 1951).

A list of the most common plants within the colony and immediately

around it has been included (Table 10).

Table 10 Associated flora

Balsam Fir, Abies balsamea

 

White Pine, Pinus strobus

 

Red Pine, Pinus resinosa

 

Austrian Pine, Pinus nigra

 

Common Cat-tail, Typha latifolia

 

Iris, Iris sp.

Black Willow, Salix nigra

 

Quaking Aspen, Populus tremuloides

 

Large-toothed Aspen, Populus grandidentata

 

White Oak, Quercus alba

 

Red Oak, Quercus rubra

 

Sassafras, Sassafras albidum

 

Large-seeded Hawthorne, Crataegus macrosperma

 

Bramble, Rubus sp.

Black Cherry, Prunus serotina

 

Yellow Sweet Clover, Melilotus offieinalis

 

White Sweet Clover, Melilotus alba

 

Flowering Spurge, Euphorbia corollata

 

Staghorn Sumac, Rhus typhina

 

Dwarf Sumac, Rhus copallina

 

Red Maple, Acer rubrum

 

Silver Maple, Acer saccharinum

 

45

Table 10 Associated flora (cont'd)

Box-elder, Acer negundo

 

Virginia Creeper, Parthenocissus uinquefolia
St. John's Wort, Hypericum sp.

Wild Carrot, Daucus carota

 

Whorled Loosestrife, L‘simachia guadrifolia

 

Ash, Fraxinus sp.

Indian Hemp, Apocynum cannabinum‘

 

Self-heal, Prunella vulgaris

 

Wild Bergamot, Honarda fistulosa

 

Bittersweet, Solanum dulcamara

 

Common Kullein, Verbascum thapsus

 

Buttonbush, Cephalanthus occidentalis

 

Common Elder, Sambucus canadensis

 

Throughwort, Eupatorium_perfoliatum

 

Goldenrod, Sol"ago sp,

Horse-weed, Eriveron canadensis

Coneflower, Rudbeckia sp.

Common Yarrow, Achillea millefolium

 

Canada Thistle, Cirsium arvense

 

Lettuce, Lactuca sp.

Summary

The life history study of a nesting colony of Green Herons in
southern Michigan was carried out from July to August, 1958, and
again from April to July, 1959.

The genus Butorides is composed of 1 species, virescens, and 5
subspecies in Nbrth.America. The current taxonomic status of the
genus is discussed.

The distributional limits of the species include most of the
Horth.American continent north of the Panama Canal Zone as well as
scattered areas of northern South America. The eastern form virescens
is found chiefly east of the Mississippi River valley. This form is
the most common summer resident heron in Michigan.

The Green Heron arrives in Hichigan in the spring during the
period from midHApril to early May. The breeding period extends from
May to the first weeks of August. Fall migration occurs from mid-
September through most of October.

A colony of 57 Green Heron nests was located on the border of a
marsh succession in Prairieville Township, Barry County, Michigan.

The area occupied was approximately 2§-5 acres of a pine planting
composed mainly of red pine, Austrian pine, and white pine. As a
result of natural succession other species of trees, shrubs, and common
weeds had grown throughout the stand.

The average height of all the nests was 11.7 feet with a standard

deviation of 1.5 feet. The average height of the nests in red and

w

Austrian pine was the same as in the white pine, 11.8 feet. There was
a significant difference in the standard deviations however. Only 5
nestings out of 57 occurred in trees or shrubs other thgn pine. Two
of these nests were in the same tree at the same height on different
seasons. No trees contained more than 1 nest at the same time.

Pre-nesting behavior, courtship, and associated activities, such
as nest-building, were not studied. These aspects are quite thoroughly
'covered in a recent publication by Keyerriecks.

The average clutch in the nests studied was 5.5 eggs with a vari~
ation from 2-5 eggs. The average eggzsize was 59.1 x 29.9 mm. In the
only determination of he time of egg-laying, a third egg was laid
between 12:00 and 4:00 PM, May 29, 1959.

The incubation period for 10 eggs was 25 days. Incubation periods
for several other eggs were determined from the approximate dates of
laying and hatching.

The young herons remain in the nest for 10 days. During this
time weight determinations for 10 young were made. The young were fed
by regurgitation. Examination of regurgitated material and a few
stomach examinations indicated that the young were fed mostly aquatic
insects, amphibians, and occasionally fish.

Movements from the nest became common after the first 10 days.
These were limited to a few feet out on supporting branches in the
tree. First attempts at flying were observed at approximately 2%
weeks of age. One young heron was seen 64 feet from the nest at 22
days after hatching.

Behavior patterns of the young are varied and include gagging,
gular fluttering, vocalizing, defecating activities, and climbing.

Each of these is discussed in the text.

48

Mortality in this nesting colony was very high. Of the 66 heron
eggs found in this study, 25 were infertile, stolen, or damaged and
deserted. Forty-three of the 56 young were found dead or missing from
the nests. At least one case of predation on heron eggs by a red
squirrel was recorded. Other possible factors are discussed.

Samples of the associated flora within the study were collected
and identified to species or genus. A list of the associated fauna
was also kept.

Several tables showing migration data, height of the nests,
collected food material, mortality data, and the associated flora and
fauna are presented. A map of the study area and a graph showing

weight increase of the young for the first 10 days are included.

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--------------- - 1951. Seasonal records of Michigan birds, summer
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------------------ 1952. Seasonal records of Michigan birds, fall, ;
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-—---- ---------- - 1955. Seasonal records of Michigan birds, spring,

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