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This is to certify that the
thesis entitled
BIOENERGETICS OF THE WILD TURKEY
IN MICHIGAN

presented by

Brian Thomas Gray

has been accepted towards fulfillment
of the requirements for

Master of Science degree in fisheries and Wildlife

 

 

Major professor

Date June 25. 1986

0-7639 MS U is an Affirmative Action/Equal Opportunity Institution

 

MSU

m

 

 

 

RETURNING MATERIALS:
Place in book drop to
remove this checkout from
your record. FINES will
be charged if book is
returned after the date
stamped below.

 

 

 

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'JUL 1 _8 3994‘

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MAY {10 3999

 

 

BIOENERGETICS OF THE WILD TURKEY

IN MICHIGAN

BY

Brian Thomas Gray

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirement
for the degree of

MASTER OF SCIENCE

Department of Fisheries and Wildlife

1986

ABSTRACT

BIOENERGETICS OF THE WILD TURKEY
IN MICHIGAN

By
Brian Thomas Gray

The bioenergetics of the eastern wild turkey (Meleagris gallopavo)

 

in Michigan was studied from December, 1983 through March, 1985.

The objective of this study was to estimate daily energy expenditure
(DEE) in relation to ambient temperature and activity of free-ranging
turkeys during winter months. This was accomplished by monitoring
metabolism and gross energy (GE) intake of captive turkeys as a function
of ambient temperature, and through time-activity observations on
free-ranging birds.

DEE models predicted juvenile females as the most susceptible
to winter starvation followed by juvenile males, adult females, and
adult males, respectively. During periods of severe cold and zero
food intake, juvenile females were predicted to succumb within 8 days,

whereas adult males were predicted to survive 20 days.

ACKNOWLEDGEMENTS

This study was funded through the Michigan Department of Natural
Resources Wildlife Division. Special thanks go to Martin Pollock,

Dave Dorn, and the work crew at the Mason Game Farm for their invaluable
help in hatching and rearing the captive flock of turkeys used in
this study.

I would like to thank Dr. Harold H. Prince for serving as my
major advisor. His much needed guidance, good humor, and sincere
friendship will be remembered always. Sincere appreciation is extended
to Mr. Carl L. Bennett, Dr. Jonathan B. Haufler, and Dr. Richard w.

Hill for serving on my graduate committee and for their helpful
suggestions and guidance. I would especially like to thank Dr. Hill
for allowing me the use of his laboratory during metabolism measurements.

Special thanks go to Dr. Donald Polin of the Poultry Science
Department. His enthusiastic help whenever consulted was a great
asset to this project.

Thanks are extended to Dave Evers, Kay Fisher, Earl Flegler,
Chris O'Rourke and Rick Rusz for field assistance and summarization
of data while at Michigan State University. I would especially like
to thank Thomas Kulowiec and Mark Sargent for their generous assistance
with field work and maintenance on numerous occasions during inclement
weather and unusual hours.

I wish to thank fellow graduate students Dean Beyer, Rick Campa,

ii

Laura Eaton, Laura Grantham, David Gordon, Thomas Kulowiec, Bobbie
Webber, and Dave Woodyard for their friendship and encouragement.

A special thank you is extended to Barbara Bara for editorial
assistance and typing this final draft.

Finally, I thank my fiancee Carolyn for all her help,
encouragement, and patience. She willingly helped with all phases
of the project from pen construction to editing. Without her assistance

this project could not have ended with as much enthusiasm as it started.

iii

LIST OF TABLES

LIST OF FIGURES

INTRODUCTION .

METHODS .

Source of Captive Turkeys

TABLE OF CONTENTS

Metabolic Measurements .

Gross Energy Intake

Time Activity Observations

RESULTS . .

Metabolism Measurements
Gross Energy Intake

Time Budgets

DISCUSSION

Metabolism Measurements
Gross Energy Intake
Time Budgets

Estimates of Total Daily Energy
Expenditure in Winter

Estimates of Winter Survival

Future Research Needs and
Management Implications

LITERATURE CITED .

iv

Page

vi

ll
14
14
17
21
25
25
28

29

31

42

47

52

LIST OF TABLES

Table Page

1. Sex, age, source and number of captive 7
turkeys used in metabolic experiments
during each seasonal period.

2. Sex, age, source and number of captive 10
turkeys used in food trials during each
seasonal period.

3. 902 (ml/g/hr) of fasted turkeys during 15
3 chronological periods at 25 °C.

4. Estimated T (°C) of fasted turkeys 18
. c . .
during 3 chronological periods.

5. Spearman correlations (rho) among activities 24
of free-ranging turkeys and climatic
variables for each time period in northern
lower Michigan. N:118 birds observed for
each correlation.

6. The abvalues calculated from the equation 27
M=aW , where M = kcal per hour, a_= constant,
W : weight in kg, and b: 0.734.

7. Sensitivity of DEE to error in estimating 36

factors for activity in adult females
during winter (DEE = 1691 kJ/bird/day).

8. Percent deviation of DEEs "estimated" by 38
the model from "actual" DEEs obtained
from captive wild turkeys during winter.

9. Models used to estimate winter DEE 40
(kJ/bird/day) for each age and sex of wild
turkey.

10. DEEs (kJ/bird/day) estimated by the model for #1

each sex x age combination of wild turkey
at various winter temperatures.

LIST OF FIGURES

Figure Page

1. Flow diagram of the Open circuit system 5
used to measure oxygen consumption in
captive wild turkeys.

2. Dairy farm used for winter behavioral 12
observations.
3. Metabolic rates (ml Oz/g/hr) of juvenile l6

and adult turkeys measured at various
temperatures during 3 chronological
periods.

4. Seasonal changes in G.E. intake, body 19
weight, and ambient temperature in
caged male (0) and female (-) turkeys
housed out-of— doors. N = 8 juvenile
females and 4 juvenile males for winter
1984, N = 5 adult females and 6 adult
males for summer 1984, and N = 7 adult
females and 5 adult males for winter 1985.

5. Percent time spent in activities by 22
turkeys during the first, middle, and
last third of the diurnal period. Data
shown are seasonal means for diurnal+period
- SE (crosshatched) and time blocks - SE
within diurnal period (solid). N = 59
turkeys of each sex observed during each
time block.

6. Estimates of expected days of survival 43
for juvenile and adult turkeys during
winter at various temperatures and
restricted levels of energy intake.

vi

INTRODUCTION

The original range of the eastern wild turkey (Meleagris gallopavo

 

silvestris) included the southern portion of Michigan's lower peninsula,

 

roughly south of a line from Saginaw Bay to Muskegon County (Leopold
1931 in Lewis 1962). The wild turkey disappeared from the Michigan
area around 1900 (Ignatoski 1973), with the last recorded observation
in Van Buren County in 1897 (Barrows 1912 in_Aldrich 1967). This
disappearance coincided with the end of a 40 year era of logging that
swept across the entire southern peninsula (Petersen 1979). As the
pine forests of the north were cleared mixed stands of oak (Quercus

spp.), beech (Fagus grandifolia), and maple (Acer spp.) developed

 

in their place, changing the composition of these northern forests.

In an effort to reintroduce turkeys in Michigan, Pennsylvania
game farm turkeys (3/4 wild hens serviced by wild toms) were released
at 15 different locations in the southern peninsula between 1954 and
1963. Fourteen of these release sites were located north of the birds'
original range in large tracts of second growth hardwoods created
by the logging era. The releases were considered successful and annual
hunting seasons have been held in designated areas since 1965. Current
distribution of the reintroduced birds remains north of the original
range, with only 1 flock of game farm descendants in the southern
part of the state (Ignatoski 1973). Bronner (1983) reported 75% of

the northern birds winter on private lands consisting of hunting clubs

2

and farm lands. This study focuses on these flocks of turkeys.

Snow depth during winter is one of the most important physical
factors influencing turkey populations in the upper midwest (Porter
et a1. 1980, Porter 1983), with depths over 25 cm greatly reducing
mobility (Austin and DeGraff 1975). Turkeys wintering in forested
areas become dependent upon localized food sources and are restricted
to these small areas during periods of deep powder snow even after
food sources become depleted (Hayden 1980). In addition to hindering
movement, heavy snowfall also makes localized winter foods such as
mast and waste grain unavailable. Northern lower Michigan receives
over 150 cm of snow annually, with accumulations over 30 cm common
from late December through early March (Stromme 1967). In late fall,
large flocks of northern Michigan turkeys return to established wintering
areas where food was available the previous year (Kulowiec and Haufler
19853). Successful flocks are associated with active farms where
grain is readily available from feedlots, corn cribs, or as waste
in the field, or private lands where artificial feeding programs are
practiced. Michigan Department of Natural Resources (MDNR) wildlife
biologists report that the majority of starvation related mortalities
occur on public lands isolated from agricultural and artificial feeding
areas. Populations wintering on these areas fluctuate according to
the severity of winter, whereas populations on private lands appear
more stable. Before the suitability of winter habitat on both public
and private lands can be adequately assessed, the energetic needs
of wintering turkeys must be quantified.

Temperature and changes in the time allocated to various activities

are the major determinants of changes in a bird's daily energy expenditure

3
(DEE). Knowledge of metabolic rates at different temperatures, coupled
with knowledge of time allocated to activities during these temperatures,
would help researchers better understand energy budgets of wild birds.
Standard methods used to estimate DEE include: (1) extrapolations
from laboratory measurements of oxygen consumption or metabolizable
energy intake, (2) time-activity studies of free-ranging birds, quantified
in energy terms by extrapolations of laboratory data, and (3) estimates
of energy consumption by indirect methods in free-living birds (King
1974). This study was designed to estimate DEE in relation to temperature
and activity of free-ranging turkeys, during winter months, using
a combination of methods 1 and 2. With this information the importance
of public lands, agricultural areas, and artificial feeding programs
to the turkeys' winter survival could be assessed, and management

plans geared toward improving the winter habitat developed.

METHODS

Source of Captive Turkeys

 

A captive flock of turkeys was established in the spring of 1983.
The flock originated from 3 sources: eggs collected from nests of wild
birds in northern Michigan, eggs obtained from the Van Atta Game Farm
located in Haslett, Michigan, and eggs obtained from the Pilarski Game
Farm located in Fairview, Michigan. All eggs were incubated and hatched
at the Mason Wildlife Facility. Poults were pedigree hatched, leg banded
and moved to brooder houses. At 2 weeks of age they were moved to
3 x 20 m outdoor pens with food and water available ad libitum. Purina
Startena was fed the first 4 weeks. Diets were shifted to Purina Turkey

Growena through the first winter and Purina Maintenance Chow thereafter.

Metabolic Measurements

 

Metabolic measurements were made in a conventional open circuit
system (Hill 1972), using a Beckman paramagnetic oxygen analyzer.
Pressurized ambient air flowed through Drierite (a drying agent), through
flowmeters (Brooks rotameters), into the metabolic chambers, back
through Drierite through an automated flow selector, through Ascarite
(used to absorb 00,), through more Drierite and into the oxygen analyzer

(Fig. 1). Two PVC metabolic chambers, measuring 32 x 64 x 40 cm for

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females and 36 x 76 x 46 cm for males, were housed inside an
environmental chamber with a temperature range of -15° C to +50° C.
Copper-constantan thermocouples with a Honeywell chart recorder were
used to monitor temperatures (: 1° C) in the metabolic chambers.
A mercury barometer was used to determine atmospheric pressure and
a mercury-in-glass thermometer was used to monitor flowmeter temperature.

Metabolic rates of turkeys were measured during 2 winter and
1 summer periods (Table 1). Winter measurements were taken from February
16 to March 18, 1984, on juvenile females. Winter tests conducted
on juvenile males and adults of both sexes were run from December 29,
1984, through March 20, 1985. Measurements during the summer were
taken on adults of both sexes from July 5 to September 10, 1984.

Test sequences of metabolic measurements are referred to as
chronological periods; "winter juvenile" and "winter adult" represent
measurements conducted on juveniles and adults during winter months,
and "summer adult" represents measurements conducted on adults during
summer. During each chronological period, metabolic measurements
were obtained at 5 target temperatures (-10° C, -5° C, +5° C, +15° C,
and +25° C) for each bird. Values at the 3 highest temperatures were
obtained sequentially while measures at the 2 lowest temperatures
were obtained on separate runs. The test schedule was randomized,
and the same test birds were not utilized more than once with a 5-day
period.

Two birds were run simultaneously through each metabolic test.
Birds were fasted 24 h prior to the metabolic measurements. Following
this, the birds were weighed to the nearest gram, transported to the

laboratory and placed into the metabolism chambers. The metabolism

7

Table 1. Sex, age, source and number of captive turkeys used in
metabolic experiments during each seasonal period.

 

 

 

 

 

Source

Season Sex Age Wild Pilarski Total
Winter Female Juvenile 2 5 7
Adult 4 5 9
Male Juvenile - 6a 6
Adult 1 5 6
Summer Female Adult 4 5 9
Male Adult 1 5 6

 

8Birds were progeny of Pilarski males x Wild females raised in captivity.

8

chambers were then placed into the darkened climate chamber. The
birds were then allowed to adjust for 3 h, as recommended by Prince
(1979). Summer metabolic measurements started after 21:50 hrs and
winter measurements after 18:00 hrs. When testing a bird at more
than 1 temperature per night (i.e., highest 3 temperatures), 1 h was
allowed for adjustment after the new target temperature was reached.
Temperatures were always lowered for successive tests and never raised
as this could result in a difference in the temperature-metabolism
slope (Pohl 1969). After the adjustment period, four 5-minute oxygen
(02) samples were collected over a 1 h period for each bird (i.e.,
one 5-minute sample was collected every 15 minutes for each bird).
The lowest 3 of the 4 02 values obtained for each bird were averaged
to obtain a mean rate of consumption for the given temperature. Mean
02 values were corrected, without knowledge of the respiratory quotient,
using the table in Hill (1972). Rate of oxygen consumption (702)
was obtained by:

70, (ml Oz/g/hr) = [corrected 0, difference x flow rate (ml/hr)

x STPl/Body weight (g)
Where STP = 273/[273 + flowmeter temp.(°C)] x Barometric pressure
(mm Hg)/760mm. 70, values were converted into energy values (kJ/g/hr)
using the following formula:

kJ/g/hr = ml Oz/g/hr x 0.02009
where ml 02 : 0.0048kcal (Hill 1976) and kcal : 4.185kJ (Scott et
al. 1982).

Least squares linear regression was used to evaluate the effect
of temperature on metabolic rate. Differences in regression equations

between sources and between sexes were tested using a t-test procedure.

9

Differences in regression equations between test periods were tested

with an analysis of covariance (Zar 1973).

Gross Energy Intake

 

Gross energy (GE) intake of captive turkeys was monitored during
1 summer and 2 winter periods (Table 2). Food consumption of juvenile
birds was measured on alternate days from January 10 to March 16, 1984.
Food consumption of adults was measured on alternate days from July 3
to August 2, 1984, and from February 20 to March 22, 1985. Purina
Turkey Growena (18.08 kJ/g) was fed ad libitum the first winter and
Purina Gamebird Maintenance Chow (16.49 kJ/g) was fed the following
summer (1984) and winter (1985). Birds were placed in individual
2 x 3 m outdoor pens during the food trials, and allowed 1 week for
adjustment. Body weight was measured every 6 days. Water or snow
was supplied ad libitum. Gross energy intake was standardized for
each bird by determining the kiloJoule intake per gram body weight
per day. Mean temperature ((max + min)/2) was recorded daily using
max/min thermometers. The effect of temperature on GE intake was
analyzed using the least squares regression techniques discussed in
Nie et al. (1975). Differences in GE intake between chronological
periods were tested in each sex using an analysis of variance design
and Duncan's Multiple Range test (Steel and Torie 1980). Differences
in GE intake between sexes and within chronological period, were tested

using the two-sample t—test (Gill 1981).

10

Table 2. Sex, age, source and number of captive turkeys used in food
trials during each seasonal period.

 

 

 

 

Source
Season Sex Age Wild Pilarski Van Atta Total
Winter Female Juvenile 4 2 2 8
Adult 3 2 2 7
Male Juvenile 1 - 3 4
Adult 1 3 1 5
Summer Female Adult 3 - 2 5

Male Adult 1 3 2 6

 

11

Time Activity Observations

 

Behavioral observations of free-ranging turkeys were made on
a 165 ha dairy farm south of Fairview, Michigan (Fig. 2). The property
consisted of a mixture of cornfields, pasture, fallow fields, and
second growth woodlots. Woodlots were characterized by red maple

(Acer rubrum), sugar maple (A, saccharum), and oak (Quercus spp.).

 

MDNR 1985 winter count estimated 500 birds wintering on the area.
This was one of the larger flocks of wintering turkeys in northern
Michigan.

Time-activity observations were made on January 26, 27; February
2, 3, 4, 16, 17, 23, 24; and March 2, 3, 11, 12, 1985. Each day (1/2
hr before sunrise to 1/2 hr after sunset) was divided into 3 equal
time blocks: (1) early morning; (2) midday; and (3) late afternoon.
Each block was further divided into 2 periods, first and last half.
One period per block was chosen randomly, without replacement, every
other sampling day, with observations made during the opposite period
the following sampling day.

Observations were made from a vehicle (Fig. 2). Five male and
5 female turkeys were observed per time block each day, weather
permitting. Each bird was observed individually for 5 minutes using
a 20-45x zoom spotting sc0pe. If a bird was lost from view before
3 minutes of observation, the data were not used and another bird
was chosen for observation. Potential sample birds were selected
by first visually estimating size of various flocks on the study site
(i.e., field, woodlot, feedlot, barn area) and using a weighted

procedure (Quinlan and Baldassarre 1984) to determine what flocks

12

       

    

  

  

   

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13
to select samples from. Once a flock was selected, the number of
samples obtained for each sex was determined by estimating the size
of the flock relative to the remaining visible birds on the study
area. For example, if a flock was estimated to contain 60% of the
visible females and 40% of the visible males, then 3 females and 2
males were sampled from the flock. Individuals in the flock were
chosen by randomly focusing the spotting scope and selecting the first
bird that came into focus.

Activity of individuals was recorded instantaneously (Altman
1974) every 15 seconds. Activities were categorized as: (l) feeding,
(2) resting, (3) comfort movements, (4) walking, (5) alert, and
(6) courtship/antagonistic. Ambient temperature (°F), barometric
pressure (mm Hg), precipitation (none, light, medium, heavy), cloud
cover (0—25%, 26-50%, 51-75%, 76-100%), and wind speed (Beaufort scale
in Platt and Griffiths 1964) were recorded at the beginning of each
individual observation.

Percent time spent per activity was obtained by dividing the
number of instantaneous recordings of each activity by the total number
of recordings. All percentage data were transformed using Arcsin
transformation before statistical analysis (Steele and Torrie 1980).

A one way analysis of variance technique (Kim and Kohout 1975)
was used to test for differences in activity levels between time periods
for each sex x activity combination. "Student's" t-tests (Nie et
al. 1975) were used to test for daily differences between sexes in
each activity category. Spearman correlations (Siegal 1956) were
used to identify relationships between climatic variables and activities

during the different periods of the day.

RESULTS

Metabolism Measurements

 

702 at 25° C did not differ (P>0.05) between sources of turkeys of
the same sex during any chronological period, therefore values for
Pilarski and Wild birds were pooled in each sex (Table 3.). 70, at
25° C also did not differ (P>0.05) between males and females within any
chronological period. 90, of juvenile turkeys in winter and adults in
summer were not significantly different (P>0.05), and both were higher
than that of adults measured in winter (P<0.05).

Within each chronological period, measurements made at 15° C

appeared to be above T (lower critical temperature) in some turkeys

lc

and below T1C in others (i.e., 902 at 15° C was equal to 70, at 25° C

in some birds, while in others 90, at 15° C was greater). Therefore,
including 15° C measurements in regression analysis resulted in smaller

regression coefficients and higher estimated T in each equation.

lcs
Due to this potential error, 90, consumption measured at 15° C was
deleted from analysis.

Metabolic readings at +5°, —5°, and -10° C were used in regression
analysis of temperature and metabolic rate. A negative linear
relationship (P<0.001) existed between temperature and 70, for all

ages and sexes of turkeys tested below the T (Fig. 3). There were

lc

no differences in regression coefficients (slopes) or elevations (P>0.05)

between sources of females or males within chronological period.
14

15

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Winter Juvonllos
0.0000 -
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Temperaturo ('C)

Fig. 3. Metabolic rates (ml Oa/g/hr) of juvenile and adult turkeys
measured at various temperatures during 3 chronological periods.

17

The regression coefficients for males, however, were significantly
lower than females (P<0.05) within each chronological period. Analysis
of covariance revealed turkeys of the same sex had equal regression
coefficents (P>0.05) across chronological periods, but the elevations
of regression equations varied (P<0.05) consistently across chronological
periods. Regression equations for adults of both sexes in summer
had the highest intercepts, juveniles tested in winter had the next
highest, and adults tested in winter, the lowest.

Lower critical temperatures were estimated by placing y equal
to 70, at 25° C and solving for x in each regression equation in Fig. 3
(Table 4). The trend for T1C across chronological periods was, from

highest to lowest, adults in summer, juveniles in winter, and adults

in winter, with females consistently the highest.

Gross Energy Intake

 

Gross energy intake and body weight of captive turkeys changed
with season (Fig. 4). Temperatures ranged from —20° C to +5° C during
the winter of 1984. Body weights of juvenile females in winter 1984
food trials averaged 3350 1 174g (i : S.E.) at the beginning and gradually
increased by 9% to 3650 1 265g 66 days later. Body weights of juvenile
males averaged 6370 i 620 g at the beginning and increased by 23%
to 7840 t 10958 at the end. GE intake during the winter of 1984 averaged
0.552 1 0.015 kJ/g/day and 0.498 f 0.017 kJ/g/day for females and
males respectively. The response of GE intake to varying temperature
was obtained by comparing mean daily GE intake over 6-day periods

with mean temperatures of those periods. The response was linear

18

Table 4. Estimated Tlc (°C) of fasted turkeys during 3 chronological
periods.

 

 

Chronological Period

 

Sex Winter Juvenile Summer Adult Winter Adult

 

Female 15 19 11

Male 11 14 7

 

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20
with the equation for females:

y a 0.5185 - 0.007lx (R2 0.129) (P<0.01)

and males:

y 0.4545 - 0.0088x (R2 = 0.242) (P<0.01)
where y = kJ/g/day, x : °C. The relation between GE intake and
temperature was likely confounded by increasing body size.
Temperatures ranged from 16.1° C to 25.6° C during the food
trials in the summer of 1984. Body weights of adult females decreased
slightly from 3250 i 143g at the beginning to 3200 i 170g at the end
of the 30-day trial. Body weights of adult males declined gradually

434g to 5660 1 371g. GE intake averaged 0.404 t 0.015

1+

from 5890

l+

and 0.388 0.013 kJ/g/day for females and males respectively. No
relationship existed (P>0.05) between temperature and GE intake.
Temperature ranged from —5.0° C to +6.1° C during the winter
1985 food trials. As in the winter of 1984, body weights increased
during the food trials. Body weights of adult females gradually increased
by 7% from 3810 : 98g at the beginning of the food trials to 4070 1 144g
at the end. Body weights of males increased by 8% from 6880 : 447g
at the beginning to 7400 : 537g at the end of the 30-day trial. GE
intake during the winter of 1985 averaged 0.524 t 0.018 kJ/g/day in
females and 0.426 t 0.019 kJ/g/day in males. No relationship existed
between temperature and GE intake during the winter of 1985.
Birds of both sexes consumed more energy, on a per gram basis,
in the winter than in summer (P<0.01). Although temperatures were
considerably lower during winter 1984 food trials than winter 1985

food trials, energy consumption of either sex, on a per gram basis,

was not different (P>0.05). Body weights of both sexes were heaviest

21
in winter and lightest in summer. In males, juvenile body weights
in winter were heavier than adults due to the source of birds used
(Table 2); Van Atta birds were heavier than Pilarski and Wild.
Although, on a per gram basis, males consistently consumed less energy
than females, only the difference during the winter of 1985 was

significant (P<0.05).

Time-Budgets

 

Observations of a flock of approximately 500 free-ranging turkeys
were made from January 26 to March 12, 1985. During this time, most
birds restricted their home range to the 160 ha farm (Fig. 1.), feeding
in the cornfields, feedlot, and barn area. At night the entire flock
roosted in the woodlot west of the barn area. The main source of
food appeared to be corn obtained by: (1) eating directly from the
corn crib in the barn area, (2) from undigested corn in cattle manure,
located in manure piles or spread on fields, or (3) waste corn in
fields. In late March, as the snow melted, turkeys foraged heavily
in exposed areas, consuming what appreared to be grasses, mast, and
waste grain. Although sex could be readily determined during the
observations, differences between adult and juvenile birds were not
distinguishable.

Temperature during the observations averaged -5.0° : 0.6° C
(i : S.E.), ranging from a low of -30° to a high of 6° C. Snow depth
averaged 29.5 cm. Percent time allocated to each of the 6 activities
remained similar (P>0.05) across daily time periods in both sexes

(Fig. 5), and mean daily activities were similar (P>0.05) between

22

 

 

 

 

 

 

Ii $.15.
Courtship/Antagonistic
107-
""-1 tr tr tr tr tr tr
1 O r- } Alert
20 Comfort

10:43_il-i-
40 1+ “ Feeding 7%

30

1%.

 

 

 

 

 

 

 

20

I I I I f

10

 

 

 

 

 

 

 

 

SW1
§.\\\\\\\\.

 

 

VVaudng

Percent Time Per Activity

20+

10

 

 

 

 

 

 

Rs.

 

 

30 1- T Resting FIT 1r}?

 

 

 

 

 

 

 

 

 

 

 

 

20-1 I 1 It _l1

Fig. 5. Percent time spent in activities by turkeys during the first,
middle, and last third of+the diurnal period. Data shown are+seasonal
means for diurnal period - SE (crosshatched) and time blocks - SE

within diurnal period (solid). N = 59 turkeys of each sex observed
during each time block.

23
sexes. Feeding was the predominant activity comprising an average
of 40% of the day in both sexes, resting was the next at 25%, followed
by walking at 17%; comfort movements comprised 10%, alert, 7.5%, and
courtship/antagonistic, 0.5%. Although turkeys occasionally flew
short distances during the observations, flight amounted to a minute
percent of the daily activities; therefore the activity was omitted
from observations.

Several activities were correlated with climatic variables within
time periods (Table 5). Temperature was correlated negatively with
comfort and resting, and positively with feeding during the first
2 diurnal periods. Precipitation was correlated negatively with comfort
and resting during the first 2 periods, but positively during the
third period. Feeding was the reverse, correlated positively with
precipitation during the first 2 periods and negatively during the
third period. Cloud cover followed the same trend as precipitation
but the correlations were not as strong.

Wind velocity was correlated negatively with percent time alert
and positively with walking during the third period. Barometric pressure
was negatively correlated with comfort during the third time period

and positively correlated with resting during the second time period.

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DISCUSSION

Metabolism Measurements

 

Measurements of oxygen consumption obtained from animals during
their normal resting period, in a thermoneutral environment, and in
a postabsorptive state, approximate the standard or basal metabolic
rate (BMR). Measurements made under these same conditions but at
air temperatures outside the thermoneutral range are a linear or
near-linear function of air temperature below the thermoneutral range
(King 1974). In this study, I refer to these measurements below
thermoneutrality as measurements of the existence metabolic rate (EMR).
Kendeigh et al. (1977) noted that although differences in BMR
between males and females are sometimes observed, their occurrences
are erratic and inconsistent except when there are pronounced differences
in body weight. Male turkeys were roughly twice the size of females
in this study, yet there was no difference in BMR per gram body weight.
The BMR within a group of related animals is strongly
weight-dependent and often adheres to the equation:
M = awb
where M = metabolic rate, W = body mass, a : constant, and b : exponent
that describes the effect of size within the group (Calder 1974).
King (1974) developed an equation for non-passerines based on Aschoff

and Pohl's (1970) equation:

25

26
kcal/h = 3.6w0'734
where W = body weight in kg. A comparison of the a_values from my
data should give some indication of the applicability of their equation
to turkeys or other large birds. I compared data from adult turkeys
used in my studies (Table 6) and found significant differences among
the calculated a_values for male and female turkeys. All §_values
from my data were lower than the value of 3.6 for non-passerines,
therefore King's equation appears to overestimate BMR in turkeys.

BMRs of adult turkeys, expressed per unit body weight (mlOZ/g/hr),
were significantly lower in winter than in summer. The ecological
significance of this is complicated by the differences in body weights
that existed between winter and summer. Males and females were 26%
and 23% heavier, respectively, in winter than summer. Therefore,
the difference in metabolism between seasons is confounded by body
size. Winter and summer BMRs of adult turkeys expressed per bird
(kJ/bird/hr), however, are not significantly different between seasons
(P>0.05, paired t-test).

Male turkeys in this study, due to their larger body size,
consistently had smaller temperature coefficients than females in
all chronological periods. Kendeigh et al. (1977) reported 24 out
of 31 species of birds reviewed had lower temperature coefficients
in winter than in summer. Temperature coefficients of turkeys in
this experiment did not differ between seasons in either sex. Regression
equations between resting metabolism and air temperature in each sex
differed between seasons due to varying elevations caused by varying
T , not varying temperature coefficients. Kendeigh et al. (1977)

lc

stated that as birds increase in weight the T Cdeclines at the same

1

27

Table 6. The aC values calculated from the equation M

M = kcal per hSur, a_= constant, W = weight

b

aWb, where

 

 

 

 

 

 

in kg, and = 0.734.
Chronological Female Male
Stage N a_ N ‘a
Adult Summer 9 2.7 i 0.05 6 3.2 i 0.05
Adult Winter 9 2.3 i 0.05 6 2.8 i 0.06
C—-+
x - S.E

28
rate in all taxa at all seasons. Male turkeys in this study had lower

Tlcs than females during all chronological periods, but a seasonal

difference in T was evident in both sexes, with winter T

1c conSlstently

lcs

lower than summer. Lower Tlcsin avian species during winter could

result from better insulation from the plumage or added body fat or

a combination of both (Pohl 1971). Kendeigh et al.'s (1977) equation

-O.1809 +

estimating T for non-passerines (TlC = 47.17W - 1.382, where

1c

w = body weight in grams) predicted T of 9.4 11.40 c for adult

lcs
males (i = 7300g) and 10.6 i 1.4° c for adult females (i = 3900g)

used in winter metabolism measurements. These figures compare reasonably
with my estimates of 7° C and 11° C for males and females, respectively.
Their equation estimates of 10.0 : 1.4° C for adult males 1; = 5400g)

and 11.1 : 1.4° C for adult females 1% = 3020g) used in summer metabolism

measurements, however, were considerably lower than my estimates of

14° C and 19° C, respectively.

Gross Energy Intake

 

Energy intake is a linear function of air temperature in a variety
of avian species. Most studies have focused on the relationship of
existence (metabolized) energy and temperature (e.g., West 1960, West
1968, Owen 1970), while a few (e.g., Hart 1962) have studied the
relationship of temperature and GE intake. I found GE intake to be
inversely related to ambient temperature during the first winter of
food trials but not the second. The second winter never had temperatures
substantially below the thermoneutral zone (i.e., i : 1.3° C); this

is probably why a relationship was not observed.

29
My captive turkeys tended to increase in weight during the winter
food trials and maintain or lose weight during the summer food trials.
Adult body weights of both sexes were approximately 25% greater during
winter experiments. Bailey and Rinell (1967) reported the same trend;
wild turkeys increase in weight throughout the winter, attaining maximum
weight just prior to mating season. Weight then declines throughout

the spring and reaches a minimum in July and August.

Time Budgets

 

Turkeys observed during the time budget studies spent most of
the day feeding in crop fields or around barnyards, and resting in
woodlots adjacent to these areas. Porter (1977) reported the same
trend; wild turkeys in southeastern Minnesota fed extensively in
cornfields during winter.

Temperature and precipitation were the weather variables most
often correlated with activity. Birds tended to feed more on mornings
with snowfall, but later in the afternoon, snowfall tended to reduce
time spent feeding. Comfort and resting activities were inversely
related to feeding activities during all 3 periods. In the morning,
when temperatures were bitterly cold, birds would remain inactive
until the sun came up or the temperature increased. In the late
afternoon, however, temperature had no measurable effect on resting,
comfort, or feeding activities.

On windy days, turkeys tended to rest on the leeward side of
hills and woodlots, with feeding patterns not markedly different.

Wind velocity or calculated wind chill were not correlated with any

30
activity. There were no correlations between barometric pressure
and activity.

Davis (1949) reported turkeys have 2 distinct periods of heavy
feeding, mid-morning and mid-afternoon. The remainder of the day
is spent resting. Mosby and Handley (1943) found the late afternoon
to be the time of heaviest feeding. Bailey (1967), however, believed
during periods of snow cover turkeys may be forced to feed or search
for food throughout most of the day. Snow completely covered the
ground during all the time-budget observation periods except March 11
and 12, when an earlier warm rain exposed patches of bare ground.

My results agree with Bailey; on the average turkeys tended to feed
at the same rate all day.

Lewis (1962) reported turkeys staying on the roost during
snowstorms and following storms when the snow was deep and soft.
Turkeys observed in this study remained active during morning and
early afternoon snowstorms, but tended to become inactive during late
afternoon storms. None of the time-budgets were conducted after a
heavy snowstorm (>10 cm) so I could not determine if deep new snow
affected activity. The average snow depth during my time budgets
was 29.5 cm. Snow depth, either less than or greater than the depths
recorded during the time budgets could affect the turkeys' activity
budgets and consequently the daily energy expenditure (DEE). Different

habitats and food availability could also potentially alter activity.

31

Estimates of Total Daily Energy Expenditure in Winter

 

Daily energy expenditure (kJ/bird/day) can be estimated from

the model:

1) DEE

where:
TR

EMR

DHL

BMR

DH
Pf
Pr
Pw
Pc
Pa

Pco

NH

BW

*This

and early spring are below the T

[(TR x DHL) + (BMR x DH) (2.2Pf + 1.5Pr + 2.2Pw + 1.8PC +

2.1Pa + 3.0PCO) + (EMR x NH)]BW

EMR - BMR, day time thermoregulatory costs (kJ/g/hr).
Resting Metabolic rate (kJ/g/hr) at temperatures below
T1C estimated by converting the appropriate equation in
Fig. 3 to energy units.

Total hours of daylight below Tlc'
Basal metabolic rate (kJ/g/hr) estimated from captive turkeys
at 25° C (Table 3).

Total hours of daylight.

Proportion of daylight spent feeding.

Proportion of daylight spent resting.

Proportion of daylight spent walking.

Proportion of daylight spent in comfort activities.
Proportion of daylight spent alert.

Proportion of daylight spent in courtship/antagonistic
activities.

Night time hours.*

Body weight of turkeys in grams.

model assumes all night time temperatures during winter

1cln wlld turkeys.

32
The energy requirements for activity (multiples of BMR) are included
as numerical coefficients in the third bracketed set, with each being
a multiplier for the proportion of daylight spent in the associated
activity.
Energy requirements for activity were estimated from data on
other species of birds. Resting has been estimated to be 1.4 x BMR

in black ducks (Anas rubripes) (Wooley and Owen 1978), 1.5 x BMR in

 

purple martins (Progene subis) (Utter and LeFebvre 1973), 1.7 x BMR

 

in ferruginous hawks (Buteo regalis) (Wakely 1978), and 2.6 x BMR

 

in willow flycatchers (Empidonax trailli) (Ettinger and King 1980).

 

I used the figure of 1.5 x BMR as an estimate of the energetic cost
of resting in wild turkeys.
Wooley and Owen (1978) estimated alertness to be 2.1 x BMR in
black ducks and Wakely (1978) estimated it to be from 2.0-2.5 x BMR
in ferruginous hawks. I used the average figure of 2.1 x BMR.
Feeding activities have been estimated to be 2.0 x BMR in American

ibis (Eudocimus albus) (Kushlan 1977), 1.3 x Existence metabolism

 

in dickcissels (Spiza americana) (Schartz and Zimmerman 1971), and

 

1.7 x BMR in black ducks (Wooley and Owen 1978). I used the factor
of 2.2 x BMR in this model because I feel turkeys have potentially
a more costly form of foraging (i.e., scratching and digging) than
the 3 other species.

I defined comfort movements in turkeys as preening, ruffling
feathers, stretching, or wing-flapping. Wooley and Owen (1978)
estimated the cost of preening and wing-flapping in black ducks to
be 1.6 x BMR and 3.0 x BMR respectively. Mugaas and King (1981)

estimated preening to be 1.8 BMR in black-billed magpies (Pica pica).

33

The energetic cost of comfort movements in this model is 1.8 x BMR
because preening composed the majority of the comfort movements that

I observed.

Wooley and Owen (1978) estimated the cost of walking and swimming

in black ducks to be 1.7 x BMR and 2.2 x BMR respectively. Mugaas

and King (1981) estimated the cost of walking in black—billed magpies
to be 2.0 x BMR and Prange and Schmidt-Nielson (1970) estimated the

cost of swimming in mallards (Anas platyrynchos) to be 3.2 x BMR.

 

I used the average figure of 2.2 x BMR as an estimate of the energetic
cost of walking in wild turkeys.

Finally, I could not find any estimates in the literature for
the energetic costs of courtship or antagonistic activities. Since
these activities are usually vigorous, an estimate of 3.0 x BMR was
assigned.

The energetic cost of molt was not included in the model. Eastern
wild turkeys in the southern parts of their range do not begin their
prenuptial molt until mid-February (Bailey and Rinell 1967). I observed
this molt beginning in early March in my captive birds, but could
not find any evidence of it occurring in the wild birds during the
time-budget analysis.

The heat increment of feeding ("SDA" or "SDE") can account for
a 10-30% increase in heat production above BMR, depending on the
composition of the diet (Barrot et al. 1938, Scott et al. 1982).

Below the thermoneutral zone, part or all of the heat increment of
feeding may be utilized for thermoregulation, but the subject is still
controversial (Calder and King 1974). For this model, I assumed it

was utilized for thermoregulation and excluded it from the model.

34

In addition to the above, this model does not account for energy
expenditures of growth nor the influences of wind, thermal radiation,
and humidity.

The relationship between heat produced as a by-product of activity
and an endotherm's thermostatic requirement has been the subject of
much confusion (Walsberg 1983). The unanswered question is whether
the waste heat of activity substitutes for the resting thermostatic
requirement of endotherms at temepratures below thermoneutrality.
Pohl and West (1973) found activity metabloism of common redpolls

(Acanthis flammea) additive to thermostatic metabolism at temperatures

 

above -30° C. In a more recent study, Bryant et al. (1985) also found

no evidence for substitution in dippers (Cinclus cinclus) and treated

 

foraging costs as additive to thermoregulatory costs. Walsberg (1977)

developed a model for phainopepla (Phainopepla nitens) which incorporated

 

2 assumptions on the interaction of cold and exercise thermogenesis.
First, exercise metabolism at low work levels of nonflight activity
were considered additive to maintenance metabolism at temperatures
'below thermoneutrality. Second, exercise metabolism of flight was
assumed to substitute for cold-induced thermogenesis. No information
was available on the relationship of cold and exercise thermogenesis
for large non-passerines, therefore I incorporated Walsberg's assumptions
into the model. If heat produced as a by-product of activity does
substitute for the thermostatic requirement of resting in turkeys,
this model will overestimate DEE.

When constructing energy budgets from time budgets, miscalculated
conversion factors for computing the energy equivalents of timed

activities can be a major source of error (Kendeigh et al. 1977,

35
Walsberg 1983). Secondly, as Williams and Nagy (1984) observed, failure
to include daytime thermoregulatory requirements could also lead to
considerable error.

I used the procedure of Ettinger and King (1980) to illustrate
the magnitude of error in estimated DEE associated with error in estimates
of conversion factors. I selected DEEs of adult females estimated
by the model, and increased each conversion factor by 50% (Table 7).

The greatest error in DEE (+ 8.8%) results from an error in quantifying
the factor for feeding, because it is a relatively costly activity,
predominating the time budget. An error this large seems unlikely,
because the factor would be equal to 3.3 x BMR, which is 65% greater
than the highest factor for foraging found in the literature for a
ground feeding bird.

Errors of DEE resulting from errors in quantifying the factors
for resting, walking, comfort, alert and courtship/antagonistic are
small. It is unlikely that all errors in power factors will be
simultaneously additive (by chance some will cancel others of opposite
sign). Ettinger and King (1980) reported a higher percent deviation
in their model by increasing each power consumption factor by 25%
than I did by increasing my model by 50%. They concluded their estimates
of DEE were accurate to within roughly 5% of the true value.

Energetics models of wintering birds have recently become of
interest to population biologists. Stalmaster (1983) modeled energy
consumption to estimate energy demands of wintering bald eagles.

His model indirectly used activity cost as being additive to energetic
costs of thermogenesis. Koplin et al. (1980) modeled the energetics

of 2 wintering raptors, also including activity costs as additive

36

Table 7. Sensitivity of DEE to errgr in estimating factors for activity
in adult females during winter (DEE : 1691 kJ/bird/day).

 

 

 

 

+ 50% Error in Estimated DEE Percent Deviation from
Factor for: (kJ/bird/day) Original Estimate

Feeding 1840 + 8.8
Resting 1755 + 3.8
Walking 1754 + 3.7
Comfort 1722 + 1.8
Alert 1718 + 1.6
Courtship/Antagonistic 1694 + 0.2

aDEE estimated using the model, with ambient temperature = -10° C,

body weight = 4500g, activity equal to my time budget observations,
and 11 hours daylight.

37
to the cost of thermogenesis. Their model's DEE estimates compared
favorably with DEEs calculated from food intake estimated from
free-ranging birds. Using an approach similar to Koplin et al. (1980),
I calculated DEE in captive birds and tested the accuracy of my model
against the calculated DEE.

Daily expenditures of captive turkeys were calculated during
periods of minimal weight change (i.e., 6—day periods during the winter
food trials when the average body weight did not change more than
t 1%) to estimate existence energy. The "actual" DEE was obtained
by estimating the ME intake (75% of the GE intake; Farrell 1974) during
this period of minimal weight change. Average ambient temperature,
body weight, activity, and approximate daylength of these periods
were entered into the model allowing for a comparison of DEE "predicted"
by the model with "actual" DEE (Table 8). Activities of captive turkeys
were assumed to equal activities of free—ranging turkeys recorded
in my observations (i.e., feeding : 40%, resting = 25%, walking = 17%,
comfort movements = 10%, alert : 7.5%, and courtship/antagonistic
= 0.5% of the diurnal period). Model estimates were lower than "actual"
DEE estimates for captive adult females and males of both age classes,
and only slightly higher for juvenile females. This discrepancy could
have resulted from the method used to estimate "actual" DEE in captive
birds. Digestive efficiency (ME/GE x 100) of a species is influenced
by many factors including season and temperature, with reports ranging
from 62% to 87%. (Kendeigh et al. 1977). If ME values in the captive
turkeys averaged 70% of the GE instead of the estimated 75%, then
my estimates of "actual" DEE would be smaller, reducing the model's

underestimation from -20% in adult females and -13% in juvenile males

38

Table 8. Percent deviation of DEEs "estimated" by the model from
"actual" DEEs obtained from captive wild turkeys during winter.

 

 

 

 

 

Sex Age Percent Deviation
Female Juvenile + 2%
Adult - 20%
Male Juvenile - 13%

Adult - 9%

 

39

to -11% and -5%, respectively. The discrepancy between "actual" DEE
and DEE estimated by the model could also have resulted from incorrect
inputs into the model. Activity budgets of the captive turkeys were
not recorded and probably differed from those of free-ranging turkeys
used in the model.

The model can be used to predict energetic demands of a specific
age or sex of turkey during the winter period (Table 9). Equations
in Figure 3 predicting 70, were converted to equations predicting
energy consumption (kJ/g/hr) and used to estimate the appropriate
EMR. 70, values from Table 3 were converted to energy values (kJ/g/hr)
to estimate the apprOpriate BMR. Models in Table 9 were used to predict
DEEs for different ages and sexes of turkeys at various winter
temperatures using activity information based on my time budgets
(feeding = 40%, resting = 25%, walking = 17%, comfort : 10%, alert
= 7.5%, and courtship/antagonistic = 0.5% of the daylight hours) (Table
10). If the average daily temperature is below the Tlc then DHL :
DH. DEEs estimated from -15° C and —30° C are based on the assumption
that the regression equation describing cost of thermogenesis remains
accurate below my lowest laboratory measurement of -14° C. Body weight
and activity are assumed constant for each sex x age combination.
Therefore the change in DEE with each temperature change is a result
of thermogenetic costs. As age and weight increase the cost of
thermogenesis, expressed as a multiple of DEE in a thermoneutral
environment, remains constant in each sex, with the cost being
considerably lower in males. For example, DEE of juvenile and adult
females at -30° C is 2.2 x DEE at thermoneutrality, while DEE of

juvenile and adult males at the same temperature is 1.7 x DEE at

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42
thermoneutrality. These results can be explained by referring back
to Figure 3. Temperature coefficients, within each sex, were equal
between adults and juveniles; and males, due to their larger body

size, had smaller temperature coefficients than females.

Estimates of Winter Survival

 

If wild turkeys experience negative energy balances during winter,
it is important for managers and biologists to understand the impacts
of limited energy intake and cold temperatures on survival.

Estimates of expected days of survival for each sex and age
of wild turkey were calculated based on the interaction of temperature
and energy intake (Fig. 6). Estimates were derived by dividing total
energy available from body reserves by rate of energy loss per day,
for each temperature. Energy loss per day was estimated by subtracting
daily energy intake (ME) from DEE. Estimates were based on the following
assumptions:

1) Juvenile females : 3200g, juvenile males : héOOg, adult females =
4500g and adult males = 8000g.
2) DEEs were estimated from equations in Table 9 based on an 11 hour
day and 13 hr night, with activities based on my time budget data
and assumed constant for all energy intake levels except 0.0%
of DEE. At 0.0% DEE, all feeding activity is shifted to resting.
3) Regression equations in Figure 3 accurately predict the metabolic
response to temperatures below my lowest measurements at -14° C.
4) Body weight losses of 35% and 25% result in death of adults and

juveniles, respectively.

43

 

 

 

 

 

 

Jinan“. Mun
Pom-Io n n 60—76—103—1 2
95 d 0!!
In...“
as -
o -
lab 15
5° :-
St at on
Income
as -
o .
l 1 I I l L

 

 

 

 

- Swan
. H-flfll

:31”

Fig. 6.. Estimates of expected days of survival for juvenile and
adult turkeys during winter at various temperatures and restricted
levels of energy intake.

44

5) Adipose tissue composes 25% and 15% of winter body weights of
adults and juveniles, respectively.

6) Turkeys succumb with 2% of the initial body weight remaining as
adipose tissue. Therefore, adults and juveniles in this example
utilize adipose tissue for energy amounting to 23% and 13% of
the body weight, respectively.

7) Adults and juveniles utilize muscle tissue for energy amounting
to the difference between the maximum reduction in body weight
before death and the percent body weight of adipose tissue utilized.

8) Adipose tissue = 31.4kJ/g.

9) Muscle tissue : 4.9AkJ/g.

Porter et al. (1980) reported reduced activity in free-ranging
turkeys experiencing negative energy budgets during midwinter in
southeastern Minnesota, but the cause is unclear. As avian species
near starvation, some exhibit a decrease in activity (Brady et al.
1978, Le Maho et al. 1981), some an increase (Ketterson and King 1977,
Stuebe and Ketterson 1982), and some, no change (Mortensen and Blix
1985). Due to the conflicting information on the relationship of
food availability and feeding activity, I kept activity levels constant
for all levels of energy intake except 0.0% of DEE. Error in estimating
activity does not change estimated survival time by more than i 1
day for any energy intake level x temperature combination.

Lehninger (1981) traced the pattern of tissue utilization in
starving mammals. First, the small stores of glucose and glycogen
are used up in less than a day. Next, body fat is utilized with body
protein degraded at minimal rates. Finally, after the fat supply

is exhausted, energy requirements of the body are met from muscle

45
protein. Brady et al. (1978) and Le Maho et al. (1981) documented
the same pattern in birds.

Mosby and Handley (1943) reported turkeys may lose one third of
their body weight during winter without permanent injury. In an
experiment conducted in Mississippi, Gardner and Arner (1968) reported
winter body weight losses averaging 21% in captive juvenile female
turkeys and 35% in captive adult females without ill effects. They did
not report temperatures during the experiment, but due to the location,
it is doubtful temperatures paralleled average northern winter
temperatures. Roberts (1958 in_Bailey and Rinell 1967) reported weight
loss of 38% body weight appeared to be the critical point of no recovery.
I set weight losses of 35% and 25% as critical for adults and juveniles,
respectively, based on reference weights of my captive birds. Cold
temperatures, combined with susceptibility to predators in the wild,
make survival below this critical mark unlikely in the northern range.

Bailey and Rinell (1967) report adult wild turkeys have a seasonal
fluctuation in body weight of about 15%, being heaviest in winter
and lightest in late summer. My captive adult turkeys underwent a
25% fluctuation during this period. Wild northern Michigan turkeys,
not existing in the benign environment of my captive birds, probably
fall in between at about 20% fluctuation. This fluctuation in body
weight can be attributed to the fluctuation of adipose tissue.

No information was available on the body composition of wild turkeys
but it is logical to assume they have minimal fat of about 5% body
weight during summer and add about 20% more before the onset of winter.
Juveniles, on the other hand, are still growing body tissue prior

to winter, therefore do not have as much body fat. I feel 15% of

46
the body weight is a reasonable estimate.

Not all body fat can be utilized by starving birds. Nonrecoverable
reserves ranging from 0.3 to 1.3% of the body weight have been reported
in small birds (Robbins 1983). I used a conservative value of 2%
for turkeys; therefore adults and juveniles were assumed to utilize
adipose tissue for energy amounting to 23% and 13% of their body wieght,
respectively. Percent body weight of protein utilized was estimated
by subtracting percent body weight of fat utilized from percent
reduction in body weight resulting in death.

Johnston (1970) reported caloric densities of avian adipose
tissue ranging from 25.5 to 38.1 kJ/g. I used the average energy
value of 31.4 kJ/g (Mortensen and Blix 1985) for turkeys. Muscle
tissue contains about 75% water, 20% protein, 4% fat, and 1% glycogen
and mineral matter (Maynard et al. 1979), giving it an energy value
of approximately 4.94 kJ/g.

Northern Michigan winters last around 100 days with temperatures
averaging -5.6° C (Stromme 1967). Figure 6 illustrates how big an
impact cold weather and a limited food supply could have on a flock
of wild turkeys. Juvenile birds during severe winters are the most
vulnerable, with adults having over twice the expected survival time
at all temperature x energy intake combinations. Juveniles and adults,
within each sex, have equal thermoregulation costs per unit body weight
at low temperatures, but adults have the survival edge due to greater
endogenous reserves (i.e., adipose and muscle tissue). Within each
age category, males have a slight edge at low temperatures due to
their lower metabolic power required for thermoregulation.

Gerstill (1942 in_Markley 1967) fasted wild turkeys and found

47
them capable of surviving at least 7 days of severe weather and 24
days at temperatures between 1° C and 10° C. In another study, Wunz
(1962 in_Markley 1967) reported turkeys could survive at least 15
days without food, but did not report temperature. Although sex,
age, and weight of the birds were not specified in these reports,

the numbers appear to fit reasonably within my estimates.

Future Research Needs and Management Implications

 

Food habits and the nutritive value of foods available to northern
Michigan turkeys in the winter should be evaluated. Although
Billingsley and Arner (1970) looked at the nutritive value and
digestibility of 8 winter turkey foods, only one of these foods is
common in northern Michigan.

Once the nutritive values of winter foods to turkeys are
determined, areas can be assessed to give an estimate of the winter
carrying capacity for turkeys. After the carrying capacity or
suitability of an area is assessed, decisions can be made whether
or not managed food plots or supplemental winter feeding are desired
to maintain or increase flock size.

Hayden and Nelson (1963) demonstrated captive wild turkeys could
live for 2 weeks without food and lose up to 40% of their normal body
weight before dying. After 2-week fasts, hens were allowed to fully
recover body weight prior to the laying period. The investigators
observed that these imposed fasts did not significantly reduce fecundity
of the surviving hens. In a similar study, Gardner and Arner (1968)

reported up to 47.8% weight loss for surviving hens. They did, however,

48

notice an effect on fecundity; egg fertility was not different, but
the number of eggs laid by birds on the marginal diet was significantly
lower than that laid by the control birds. Unlike Hayden and Nelson,
Gardner and Arner maintained birds on marginal diets through the egg
laying period and never allowed the birds to recover the lost body
weight. Therefore, it appears hens can lose significant amounts of
body weight during winter without affecting fecundity as long as they
can regain it prior to the laying period.

The average date of initiation of laying in northern Michigan
wild turkeys begins around April 20 (Kulowiec and Haufler 1984, 19859).
Therefore, females have about 1 month to recover from winter before
the onset of laying. The quantity and nutritive value of foods
available to northern turkeys at this time of year should also be
assessed in the future to determine if this is a nutritionally stressful
or productive time for hens. If it is deemed a nutritionally stressful
period, then food plots that remain covered during deep snow, only
becoming accessible after the thaw, such as chufa and winter wheat,
might be desirable.

Small, mature stands of conifers such as white or red pine,
in close proximity to feeding areas are desirable as winter roosting
habitat. Wunz and Hayden (1975) found conifer stands to be preferred
roosting cover during harsh winters. I also observed heavy utilization
of conifers for roosting cover during my time budget observations.
These roosts reduce thermal radiation losses compared to regular
hardwoods. By selecting coniferous roosts, turkeys conserve energy,
thus reducing energy expenditure.

Lewis (1962) found open streams and seeps or springs to be an

49
important winter habitat of turkeys in southwestern Michigan. If
these areas exist during winter in northern Michigan they will probably
be utilized.

Periodic winter mortality due to starvation is a common occurrence
in northern turkey populations. During severe winters, over 40%
mortality may occur in isolated northern flocks (Wunz and Hayden 1975,
Austin and DeGraff 1975, Porter 1983) as a result of malnutrition.

If management goals are to stabilize as well as raise this fluctuating
northern Michigan population, managed food plots or supplemental winter
feeding might be necessary.

Considerable debate has arisen concerning winter starvation
losses and the problem of providing supplementary food for turkeys
during prolonged periods of deep snow. Winter feeding stations are
viewed by most biologists as undesirable. Arguments point out that
they are expensive, impractical, inefficient, and promote disease
transmission. Emergency winter feeding stations operated only during
severe weather have proven ineffective. If feeding stations are to
be effective at all, they must be maintained the entire winter, not
just during periods of severe weather. If not, stations often remain
isolated from turkeys just when they are needed most (Wunz and Hayden
1975).

Food plots or plantings that remain accessible during periods
of prolonged deep snow seem to be the most attractive management tool.
Porter et al. (1980) reported low winter mortality in flocks of turkeys
feeding in standing cornfields, suggesting these areas constitute
an important feeding habitat. They felt small, appropriately placed

corn food plots could provide an effective means of maintaining

50
populations in areas of prevalent deep snow.

Indeed, planting food plots on public lands or paying farmers
to leave portions of their crops in the fields, seems more cost
effective than buying grain from elevators and redistributing it.
Arguments that deer will feed in these plots are a major consideration.
Local deer populations would be a factor in determining size or
feasibility of winter food plots. Deer can be beneficial by creating
paths through deep snow allowing turkeys easier mobility. Deer also
can efftively dig into snow, uncovering food normally inaccessible
to turkeys. But, large numbers of deer in areas with small numbers
of turkeys would make winter food plots impractical. Food plots are
also attractive because they do not concentrate birds at a single
focal point like feeders, thus limiting easy predation and disease
transmittal.

Use-days (Prince 1979) can be calculated to determine the size
of food plots needed in specific areas. Use-days for turkeys can
be calculated according to the equation:

(bird-days/ha) : [ME of Food (kJ/g) x Yield (g/ha)] /

DEE (kJ/bird-/day).

CrOp yield data must be converted to dry weight values for inclusion

in the equation (Prince 1979). Yield represents the net yield to
turkeys; therefore estimated losses to deer and other wildlife should
be considered. DEE represents the predicted average energy expenditure,
per day, over the entire winter obtained from equations in Table 9.
Projected temperature, daylength, and activity levels are entered

into the appropriate equations to determine average DEE for each sex

and age of wild turkey. For example, if a cornfield is planted that

51

yields a net of 3,750,000 g/ha (ME of corn : 14.1 kJ/g), the total
energy available to turkeys would be 52,875,000 kJ/ha. Using activities
based on my time budget observations and assuming temperature averages
-5° C and daylight 11 hours, then this area would be capable of
supporting 322 adult females/ha or 203 adult males/ha for a 90 day
period.

Use-days can also be used to calculate winter carrying capacity
of natural areas, such as hardwood stands, once the nutritive values

of natural foods are determined.

LITERATURE CITED

Aldrich, J. W. 1967. Historical background. Pp. 3-16. In_Oliver
H. Hewitt, ed., The wild turkey and its management. The Wildl.
Soc. 589pp.

Altman, J. 1974. Observational study of behavior; sampling methods.
Behavior 99:228-295.

Aschoff, J., and H. Pohl. 1970. Rythmic variations in energy
metabolism. Fed. Proc. 29:1541-1552.

Austin, D. E., and L. W. DeGraff. 1975. Winter survival of wild
turkeys in southern Adirondacks. Natl. Wild Turkey Symp.
3:55-60.

Bailey, R. W. 1967. Behavior. Pp. 93-111. In_01iver H. Hewitt,
ed., The wild turkey and its management. The Wild. Soc. 589pp.

, and K. T. Rinell. 1967. Events in the turkey year. Pp.
73-92. In_01iver H. Hewitt, ed., The wild turkey and its
management. The Wildl. Soc. 589pp.

Barrott, H. G., J. C. Fritz, and E. M. Pringle. 1938. Heat production
and gaseous metabolism of young male chickens. J. Nutri.
15:145-167.

Billingsley, B. B., Jr., and D. H. Arner. 1970. The nutritive value
and digestibility of some winter foods of the eastern wild turkey.

Brady, L. T., D. R. Romsos, P. S. Brady, W. G. Bergen, and G. A.
Leveille. 1978. The effects of fasting on body composition,
glucose turnover, enzymes, and metabolites in the chicken.

J. Nutri. 108:648-656.

Bronner, W. N. 1983. Summary of wild turkey management workshop.
Mich. Dept. of Nat. Resour. Typewritten manuscript. 16pp.

Bryant, D. M., C. J. Hails, and R. Prys-Jones. 1985. Energy
expenditure by free-living dippers (Cinclus cinclus) in winter.
Condor 87:177-186.

 

Calder, W. A., III. 1974. Consequences of body size for avian
energetics. Pp. 86-151. IQ_R. A. Paynter, Jr., ed., Avian

52

53
energetics. Nuttall Ornithol. Club Publ. 15. 334pp.

, and J. R. King. 1974. Thermal and caloric relations of
birds. Pp. 259-413. IQ_D. S. Farner and J. R. King, eds.,
Avian biology. New York, Academic Press.

Davis, H. E. 1949. The american wild turkey. Small Arms Tech.
Publ. Co., Georgetown, S. C. 328pp.

Dejong, A. A. 1976. The influence of simulated solar radiation on
the metabolic rate of white-crowned sparrows. Condor

Ettinger, A. 0., and J. R. King. 1980. Time and energy budgets of
the willow flycatcher during the breeding season. Auk
97:535-546.

Farell, D. J. 1974. General principles and assumptions of calorimetry.
In_T. R. Morriss and B. M. Freeman, eds., Energy requirements
of poultry. Br. Poul. Sci. Ltd. 199pp.

Gill, J. L. 1981. Design and analysis of experiments in the animal
and medical sciences, Vol. I. Iowa State Univ. Press, Ames,
IA. 410pp.

Gardner, D. T., and D. H. Arner. 1968. Food supplements and wild
turkey reproduction. Trans. N. Am. Wildl. Conf. 33:250-258.

Hart, J. S. 1962. Seasonal acclimation in four species of small
wild birds. Physiol. 2001. 35:224-236.

Hayden, A. H. 1980. Dispersal and movements of wild turkeys in
northern Pennsylvania. Transactions of the Northeast Sect.
of the Wildl. Soc. 37:258-265.

Hayden, H., and E. Nelson. 1963. The effects of starvation and
limited rations on reproduction of game farm wild turkeys.
Proc. NE Wildl. Cong., Portland, ME.

Hill, R. W. 1972. Determination of oxygen consumption by use of
the paramagnetic oxygen analyzer. J. Appl. Physiol.
33:261-263.

. 1976. Comparative physiology of animals: an environmental
approach. Harper and Row, New York. 656pp.

Ignatoski, F. J. 1973. Status of wild turkeys in Michigan.
Pp. 49-53. Ig_Glen C. Sanderson and Helen C. Schultz, eds.,
Wild turkey management: current problems and programs.
Univ. of Mo. Press, Columbia.

Johnston, D. W. 1970. Caloric density of avian adipose tissue.
Comp. Biochem. Physiol. 34:827-832.

54

Kendleigh, S. C., V. R. Dol'Nik, and V. M. Gavrilov. 1977. Avian
energetics. Pp. 127-204. In_Jan Pinowski and S. Charles
Kendeigh, eds., Granivorous birds in ecosystems. Cambridge
Univ. Press, London.

Ketterson, E. D. and J. R. King. 1977. Metabolic and behavioral
responses of fasting in the white-crowned sparrow (Zonotrichia
leucophrys gambelli). Physiol 2001. 50:115-129.

 

 

Kim, J. and F. J. Kohout. 1975. Analysis of variance and covariance:
subprograms anova and oneway. Pp. 398-433. In_Norman H. Nie,
C. H. Hull, J. G. Jenkins, K. Steinbrenner, and D. H. Bent,
eds., Statistical package for the social sciences. McGraw-Hill,
Inc., New York.

King, J. R. 1974. Seasonal allocation of the time and energy resources
in birds. Pp. 4-70. -I_n R. A. Paynter, J1". ’ ed. ’ AVian
energetics. Nuttal Ornithol Club. Pupl. 15. 334pp.

Koplin, J. R., M. W. Collopy, A. R. Barmmann, and H. Levenson. 1980.
Energetics of two wintering raptors. Auk 97:795-806.

Kulowiec, T. G. and J. B. Haufler. 1984. Habitat utilization and
population characteristics of resident Michigan turkeys.
Biannual progress report to Mich. Dept. of Nat. Resour. 20pp.

. 1985a, Winter dispersal movements of wild turkeys in
Michigan's northern lower peninsula. Pp. 145-153. Ig_James
Earl and Mary C. Kennamer, eds., Proc. Fifth Natl. Wild Turkey

Symp.

19852, Habitat utilization and population characteristics
of resident Michigan turkeys. Biannual progress report to Mich.
Dept. of Nat. Resour. 15pp.

Kushlan, J. A. 1977. Population energetics of the American white
ibis. Auk 94:114-122.

Lehninger, A. L. 1981. Biochemistry. Worth Publishers, Inc., New
York. 1104pp.

Le Maho, Y. V., H. Vu Van Kha, H. Koubi, G. Dewasmes, J. Girard,
P. Ferre, and M. Cagnard. 1981. Body composition, energy
expenditure, and plasma metabolites in long-term fasting geese.
Am. J. Physiol. 241:342—354.

Lewis, J. C. 1962. Wild turkeys in Allegan County, Michigan. M.S.
Thesis, Mich. State Univ., E. Lansing. 35pp.

Maynard, L. A., J. K. Loosli, H. F. Hintz, and R. G. Warner. 1979
Animal nurtition. McGraw-Hill Book Co., New York. 602pp.

Markley, M. H. 1967. Limiting factors. Pp. 199-244. In_Oliver

55

H. Hewitt, ed., The wild turkey and its management. The Wildl.
Soc. 589pp.

Mortensen, A., and A. S. Blix. 1985. Seasonal changes in the effects
of starvation on metabolic rate and regulation of body weight
in Svalbard ptarmigan. Ornis Scand. 16:20-24.

Mosby, H. S., and C. 0. Handley. 1943. The wild turkey in Virginia:
its status, life history and management. Va. Comm. Game and
Inland Fish., Richmond. 281pp.

Mugaas, J. N., and J. R. King. 1981. The annual variation in daily
energy expenditure of the black-billed magpie: a study of thermal
and behavioral energetics. Stud. Avian Biol. 5:1-78.

Nie, N. H., C. H. Hull, J. G. Jenkins, K. Steinbrenner, and D. H.
Bent. 1975. Statistical package for the social sciences.
McGraw-Hill Book Co., New York. 675pp.

Owen, R. B., Jr. 1970. The bioenergetics of captive blue-winged
teal under controlled and outdoor conditions. Condor 72:153-163.

Petersen, E. T. 1979. Hunter's heritage, a history of hunting in
Michigan. MUCC, Lansing, MI. 56pp.

Platt, R. B., and J. F. Griffiths. 1964. Environmental measurement
and interpretation. Reinhold Publ. Co., New York. 235pp.

Pohl, H. 1969. Some factors influencing the metabolic response to
cold in birds. Fed. Proc. Fed. Am. Socs. Exp. Biol. Med.
28:1059-1064.

. 1971. Seasonal variation in metabolic functions of bramblings.
Ibis 113:185-193.

, and G. C. West. 1973. Daily and seasonal variation in
metabolic response to cold during rest and forced exercise in
the common redpoll. Comp. Biochem. Physiol. A. 45:851-867.

Porter, W. F. 1977. Utilization of agricultural habitats by wild
turkeys in southeastern Minnesota. XIII Int. Congr. Game Biol.
13:319-323.

. 1983. Effects of winter conditions on reproduction in a
northern wild turkey population. J. Wildl. Manage.
47:281-290.

, R. D. Tangen, G. C. Nelson, and D. A. Hamilton. 1980. Effects
of corn food plots on wild turkeys in the upper Mississippi
Valley. J. Wildl. Manage. 44:456-462.

Prange, H. D., and K. Schmidt-Nielson. 1970. The metabolic cost of
swimming in ducks. J. Exp. Biol. 53:763-777.

56

Prince, H. H. 1979. Bioenergetics of postbreeding dabbling ducks.
Pp. 103-117. I9_T. A. Bookhout, ed., Waterfowl and wetlands-an
integrated review. Proc. 1977 Symp., Madison Wisc., N. Cent.
Sec. The Wildl. Soc. 147pp.

Quinlan, E. E., and G. A. Baldassarre. 1984. Activity budgets of
nonbreeding green-winged teal on playa lakes in Texas. J.
Wildl. Manage. 48:838-845.

Robbins, C. T. 1983. Wildlife feeding and nutrition. Academic Press,
New York. 343pp.

Schartz, R. L., and J. L. Zimmerman. 1971. The time and energy budget
of the male dickcissel (Spiza americana). Condor 73:65-76.

 

Scott, M. L., M. C. Nesheim, and R. J. Young. 1982. Nutrition of
the chicken. M. L. Scott and Assoc. Ithaca, NY. 312pp.

Siegal, S. 1956. Non-parametric statistics. McGraw-Hill Book Co.,
New York. 312pp.

Stalmaster, M. V. 1983. An energetics simulation model for managing
wintering bald eagles. J. Wildl. Manage. 47:349-359.

Steele, R. G. D., and J. H. Torrie. 1980. Principles and procedures
of statistics. McGraw-Hill Book Co., New York. 633pp.

Stromme, N. D. 1967. Climate of Michigan. U. S. Dept. of Comm.,
Washington, D. C. 25pp.

Stuebe, M. M., and E. D. Ketterson. 1982. A study of fasting in
tree sparrows (Spizella arborea) and dark-eyed juncos (Junco
hyemalis): Ecological implications. Auk 99:299-308.

 

Utter, J. M., and E. A. Lefebvre. 1973. Daily energy expenditure
of purple martins (Progene subis) during the breeding season:
estimates using D20T8 and time budget methods. Ecology
54:597-604.

 

Wakely, J. S. 1978. Activity budgets, energy expenditures, and energy
intakes of nesting ferruginous hawks. Auk 95:667-676.

Walsberg, G. E. 1977. Ecology and energetics of contrasting social
systems in PhainOpepla nitens. Univ. Calif. Berkeley Publ.
2001. 108:1-63.

 

. 1983. Ecological energetics: what are the questions?
Pp. 135-158. Ig_Alan H. Brush and George A. Clark, Jr., eds.,
Perspectives in ornithology. Cambridge Univ. Press, Cambridge.

West, G. C. 1960. Seasonal variation in the energy balance of the
tree sparrow in relation to migration. Auk 77:306-329.

57

. 1968. Bioenergetics of captive willow ptarmigan under natural
conditions. Ecology 49:1035-1045.

Williams, J. B., and K. A. Nagy. 1984. Daily energy expendutire
of savannah sparrows: comaprison of time-energy budget and
doubly-labeled water estimates. Auk 101:221-229.

Wooley, J. B., and R. B. Owen, Jr. 1978. Energy costs of activity
and daily energy expenditure in the black duck. J. Wildl.
Manage. 42:739-745.

Wunz, G. A., and A. H. Hayden. 1975. Winter mortality and supplemental
feeding of turkeys in Pennsylvania. Natl. Wild Turkey Symp.

Zar, J. H. 1973. Using regression techniques for prediction in
homeotherm bioenergetics. Pp. 115-133. In_James A. Gessamen,
ed., Ecological energetics of homeotherms: a view compatible
with ecological modeling. Mono. Ser. Utah St. Univ. Press.
Logan, UT. Vol. 20.