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Effects of Temperature and Food on Avian Incubation Behavior

Permanent Link: http://ufdc.ufl.edu/UFE0021465/00001

Material Information

Title: Effects of Temperature and Food on Avian Incubation Behavior
Physical Description: 1 online resource (30 p.)
Language: english
Creator: Londono, Gustavo
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2007

Subjects

Subjects / Keywords: avian, behavior, egg, embryo, food, incubation, nest, tempreture
Zoology -- Dissertations, Academic -- UF
Genre: Zoology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Avian incubation behavior is thought to be influenced mainly by ambient temperature and food availability. Field studies, however, have generated contradictory results and no general agreement about the relative importance of food and temperature influence and on how different components of incubation behavior are affected by each. Therefore, we experimentally increased both food availability and ambient temperature during incubation in the Northern Mockingbird (Mimus polyglottos). Our results demonstrated that both food availability and temperature influence incubation behavior. Increasing food availability enabled females to spend more time on the nest and in self-maintenance activities when off the nest. Increasing heat caused females to spend less time on the nest and to make more trips to and from the nest. When both food and temperature were increased, their effects on incubation time offset each other. These changes in incubation patterns had little effect on fitness, although embryo mass was lowest in the treatment in which only heat was increased, suggesting that heat may stress embryos, but not when extra food is also provided. Perhaps the reason why previous studies present contradictory results is because food and temperature offset each other in complex ways that could obscure their effects on incubation behavior.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Gustavo Londono.
Thesis: Thesis (M.S.)--University of Florida, 2007.
Local: Adviser: Robinson, Scott K.
Local: Co-adviser: Levey, Douglas J.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2007
System ID: UFE0021465:00001

Permanent Link: http://ufdc.ufl.edu/UFE0021465/00001

Material Information

Title: Effects of Temperature and Food on Avian Incubation Behavior
Physical Description: 1 online resource (30 p.)
Language: english
Creator: Londono, Gustavo
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2007

Subjects

Subjects / Keywords: avian, behavior, egg, embryo, food, incubation, nest, tempreture
Zoology -- Dissertations, Academic -- UF
Genre: Zoology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Avian incubation behavior is thought to be influenced mainly by ambient temperature and food availability. Field studies, however, have generated contradictory results and no general agreement about the relative importance of food and temperature influence and on how different components of incubation behavior are affected by each. Therefore, we experimentally increased both food availability and ambient temperature during incubation in the Northern Mockingbird (Mimus polyglottos). Our results demonstrated that both food availability and temperature influence incubation behavior. Increasing food availability enabled females to spend more time on the nest and in self-maintenance activities when off the nest. Increasing heat caused females to spend less time on the nest and to make more trips to and from the nest. When both food and temperature were increased, their effects on incubation time offset each other. These changes in incubation patterns had little effect on fitness, although embryo mass was lowest in the treatment in which only heat was increased, suggesting that heat may stress embryos, but not when extra food is also provided. Perhaps the reason why previous studies present contradictory results is because food and temperature offset each other in complex ways that could obscure their effects on incubation behavior.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Gustavo Londono.
Thesis: Thesis (M.S.)--University of Florida, 2007.
Local: Adviser: Robinson, Scott K.
Local: Co-adviser: Levey, Douglas J.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2007
System ID: UFE0021465:00001


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EFFECTS OF TEMPERATURE AND FOOD ON AVIAN INCUBATION BEHAVIOR


By

GUSTAVO ADOLFO LONDONO


















A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2007

































2007 Gustavo Adolfo Londofio












ACKNOWLEDGMENTS

I thank S. Robinson and D. Levey for their support and advice. I also thank J. Gillooly for

suggestions to improve earlier versions of this thesis. Field work data collection was possible

thanks to the help of J. Ungvari-Martin, M. R. Hiersoux, A. Savage, M. Phillips, and D.

DeSantis. Financial support was provided by the Ordway laboratory, the Zoology Department,

Animal Behavior Society, and Brian Riewald and John Paul Olowo Memorial Fund research

grants.










TABLE OF CONTENTS

page

A CK N O W LED G M EN T S .................................................................. ........... .............. .....

LIST OF FIGURES .................................. .. .... ... ...............5

ABSTRAC T ........................................................................ 6

CHAPTER

1 IN TR OD U CTION ............... .............................. .............. .................. .......7

2 STU D Y SITE A N D M E TH O D S............................................ ...........................................10

3 R E S U L T S ..............................................................................................15

In cu b atio n T im e ................................................................................................... ........... 15
B e h av io rs ................... ...................1...................6..........
O th er M easu rem en ts ............................................................................................................... 16

4 D ISC U S SIO N ............................................................................... 2 1

Incubation T im e .....................................................................................2 1
Effects of Supplem ent Food .........................................................................................21
E effects of Supplem ent H eat ........................................................................................ 22
Interactions Food and Temperature ................................. ................................. 22
Behaviors during Recess from Incubation.............................. ................... 23
N est P red action ................................................................................ 2 4
C o n c lu sio n s ..............................................................................2 4

R E F E R E N C E S ..........................................................................26

B IO G R A PH IC A L SK E T C H .................................................................................................... 30

















4









LIST OF FIGURES


Figure page

3-1 Mean incubation times during ten days of the different experimental females ...............17

3-2 Mean number of trips and trip length during ten continuous day of incubation among
treatm ents .......... ............ ............................................... .......... ....... .. 18

3-3 Average female time spent during incubation recesses, throughout eight hours of
observation among treatments on different behaviors .............................. ..... .......... 19

3-4 Embryo mass among treatments after ten days of continuous incubation......................20









Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

EFFECTS OF TEMPERATURE AND FOOD ON AVIAN INCUBATION BEHAVIOR

By

Gustavo Adolfo Londofio

August 2007

Chair: Scott Robinson
Cochair: Douglas Levey
Major: Zoology

Avian incubation behavior is thought to be influenced mainly by ambient temperature and

food availability. Field studies, however, have generated contradictory results and no general

agreement about the relative importance of food and temperature influence and on how different

components of incubation behavior are affected by each. Therefore, we experimentally increased

both food availability and ambient temperature during incubation in the Northern Mockingbird

(Mimuspolyglottos). Our results demonstrated that both food availability and temperature

influence incubation behavior. Increasing food availability enabled females to spend more time

on the nest and in self-maintenance activities when off the nest. Increasing heat caused females

to spend less time on the nest and to make more trips to and from the nest. When both food and

temperature were increased, their effects on incubation time offset each other. These changes in

incubation patterns had little effect on fitness, although embryo mass was lowest in the treatment

in which only heat was increased, suggesting that heat may stress embryos, but not when extra

food is also provided. Perhaps the reason why previous studies present contradictory results is

because food and temperature offset each other in complex ways that could obscure their effects

on incubation behavior.









CHAPTER 1
INTRODUCTION

Embryonic development in birds is unique among vertebrates because it typically requires

direct transfer of body heat from incubating adults (Deeming, 2002a; Turner, 2002). The

energetic costs of incubation have been generally overlooked because they are thought to be far

lower than the more obvious costs of feeding young. Recent studies, however, suggest that

incubation is energetically costly (Williams, 1996; Thomson et al., 1998; Tinbergen and

Williams, 2002) and that incubation behavior influences the probability of predators finding the

nest (Martin et al., 2000; Muchai and Plessis, 2005; Rastogi et al., 2006). Because time and

energy invested in incubation means less time and energy for energy intake (foraging) and self

maintenance, incubating birds face a trade-off between parental and self care (Williams, 1996;

Tinbergen and Williams, 2002; Turner, 2002).

Elucidating this life history trade-off requires understanding what influences incubation

rhythms (Martin, 2004), defined as the length and temporal pattern of incubation bouts. Two

factors that play important roles in incubation rhythms are ambient temperature and food

availability (Skutch, 1962; Lack, 1968; Grant, 1982; Martin, 1987; Weathers and Sullivan, 1989;

Conway and Martin, 2000a; Conway and Martin, 2000b; Deeming, 2002b; Eikenaar et al., 2003;

Lloyd and Martin, 2004; Martin, 2004; Nagy and Holmes, 2005; Zimmerling and Ankney,

2005). Ambient temperature influences energy expenditure during incubation and embryonic

growth during recesses from incubation (Baernand, 1959; Weeden, 1966; Drent, 1970; Vleck,

1981a; Zebra and Morton, 1983; Reid et al., 1999; Conway and Martin, 2000a; Tinbergen and

Williams, 2002; Cresswell et al., 2004). In contrast, food availability controls the rate of energy

acquisition and hence the times off the nest and the time available for other self-maintenance

activities (Skutch, 1962; Martin, 1987; Weathers and Sullivan, 1989; Nilsson, 1994; Sanz, 1996;









Cucco and Malacarne, 1997; Eikenaar et al., 2003; Zimmerling and Ankney, 2005; Rastogi et al.,

2006; Chalfoun and Martin, 2007). Conway and Martin (2000a) concluded that incubation

rhythm depended on ambient temperature rather than food. The effects of temperature, however,

were non-linear and explained only a small proportion of variation in incubation rhythm among

species. The same authors proposed that food does not explain variation in incubation rhythm, at

least among species (Conway and Martin, 2000b). Within species, however, food can affect

incubation rhythm (Conway and Martin, 2000a; Zimmerling and Ankney, 2005; Rastogi et al.,

2006). Therefore, there are contradictory results and no general agreement about the relative

contributions of food and temperature on avian incubation behavior.

We suggest that much of the confusion about the roles of food and temperature stems from

the assumption that these two factors act independently or the belief that one factor overwhelms

the effects of the other. Yet the relative importance and potential interaction of food and

temperature are impossible to judge in the absence of experiments that manipulate both factors

simultaneously (Martin, 1987; Conway and Martin, 2000a; Wiebe and Martin, 2000; Martin,

2004). We are not aware of any studies designed in such a way. Also, most studies of incubation

focus on quantifying when birds are on or off the nest and generally do not attempt to describe

behaviors when off the nest. Because behaviors that occur off the nest likely influence behaviors

on the nest, both should be considered part of incubation behavior -- both can have a strong

influence on nest survival and adult fitness (Franks, 1967; Vleck, 1981a; Davis et al., 1984;

Cucco and Malacarne, 1997; Nagy and Holmes, 2005; Zimmerling and Ankney, 2005).

Our primary objective was to evaluate experimentally the interaction and relative

importance of food availability and temperature on avian behavior during incubation. We

hypothesized that both food and temperature affect incubation behavior. We tested three









predictions: Prediction 1: Females on territories with high food availability will spend more

time on the nest and more time doing other potentially fitness-enhancing behaviors such as

preening or defending the nest because hunger levels and foraging times will be reduced.

Prediction 2: Females on nests in hotter microclimates will decrease time on nest and increase

the total number of trips to the nest per day because metabolic needs increase at high

temperatures, as predicted by Conway and Martin (2000a). Furthermore, females in hotter

microclimates, when on the nest, should spend more time regulating nest temperature through

behavioral responses such as panting or egg shading (Franks, 1967; Vleck, 1981a; Davis et al.,

1984). Prediction 3: Females that experience both hot microclimates and high food abundance

should spend an intermediate amount of time on the nest. The reasoning behind this last

prediction is that food and heat influence time on the nest in opposite directions (predictions 1

and 2), with food increasing time on the nest (Zimmerling and Ankney, 2005; Rastogi et al.,

2006) and heat (high temperatures) increasing on and off-bouts, which decreases time on the nest

(Conway and Martin, 2000a).

We tested these predictions by experimentally manipulating food availability and nest

microclimate of Northern Mockingbirds (Mimuspolyglottos), a species in which only females

incubate and males do not provide food to incubating females.









CHAPTER 2
STUDY SITE AND METHODS

This study was conducted between April 1 and July 15 in 2005 and 2006 on the University

of Florida campus in Gainesville, Florida (N290 38' 267"; W 082 21' 984"). The campus has

ideal mockingbird habitat: large expanses of mowed grass for foraging and scattered shrubs for

nesting.

The study area was divided in six sections and, once per week, all shrubs and trees within

each section were searched for nests. Each new nest, either under construction or with an

incomplete clutch (1-2 eggs), was randomly assigned to one of four experimental treatments in a

2 x 2 factorial design: Food increase (food+), heat increase (heat+), food and heat increase

(food+/heat+), and neither food nor heat increase (control). Food+ nests had a feeder placed

within 2 to 5 m. Feeders consisted of a plastic food storage container mounted 1.5 m above the

ground on a PVC pipe. They were placed when nests were first found and supplied daily with

mealworms (Tenibrio molitor). Based on preliminary observations of the number of mealworms

consumed by a pair of mockingbirds, we placed 160 mealworms (approximately 17g) in each

feeder every day. Mealworms have an energetic value of 11.6 kJ/g and birds can metabolize a

minimum of 71% of the energy available in an average insect (Bell 1990); our provision of 160

mealworms therefore would provide the mockingbird pair with about 5.83 kJ/h of additional

energy. Female mockingbirds consumed 7.50.68 (se) mealworms per hour.We calculated the

BMR (basal metabolic rate) for an insectivorous bird of 48g (eq. 6; McNab, 2005) to be 1.83

kJ/h. Thus, assuming that energetic requirements during incubation are three times higher than

the BMR (Williams, 1993; Piersma and Morrison, 1994), we estimated that female mockingbirds

spent 5.49 Kj/h during the incubation period. So, mealworms provided approximately 53% of the

daily energy expended by the female during incubation.









Feeders were used exclusively by the pair of mockingbirds at the nearest nest, except in a

few cases when juveniles from a pair's previous clutch also used the feeder. In those cases, an

extra 8g of mealworms were placed in the feeder. Because high temperatures can kill

mealworms in the feeders and because mockingbirds usually do not eat dead mealworms, half of

the mealworms were placed in the feeders before sunrise and the remaining half were placed in

the early afternoon. Typically, most or all of the mealworms had been consumed by the time

more were added.

Heat+ nests received an 18 watt bulb in a 47 x 32.2mm (length x diameter) cylindrical

aluminum tube on the day the third egg was laid, when the likelihood of nest abandonment was

low. The bulb and cylinder were placed directly under the nest, touching nest material,

approximately 30mm from the eggs. After the clutch was complete and incubation had started,

the bulb was turned on shortly before sunrise (0600) and remained on until the battery was

drained, approximately 8 hours later. When the bulb was on, the nest chamber experienced a

temperature of approximately 35C, which corresponds to the daytime high temperature at the

study site in late summer, when most mockingbirds stop breeding. Ambient temperature ranged

from 17.0 to 37.1 C (average: 26.6; Std. Dev. = 1.2) during the study period. Nests that did not

receive a heater (food+, and control nests) received a sham heater. Food+/Heat+ nests received

both a feeder and a heater; control nests received neither.

All nests had two thermal sensors (39.5x7.1mm), one internal and one external, connected

to a H8 4-Channel Hobo data logger (Onset Computer Corporation). Sensors were placed in

nests the day the third egg was laid and recorded temperature every minute. The internal sensor

was attached to the nest wall just above the eggs. It provided two types of information:

incubation temperature and the time at which the incubating bird left or returned to the next, as









detected by rapid temperature shifts of at least 1.50C (see below). The external sensor was

attached to the outside nest wall at the same height as the internal sensor, and shielded from the

heater. It provided data on ambient temperature in the immediate vicinity of the nest.

All treatments lasted ten days, when all eggs were collected for examination of embryo

development (see below). All nesting pairs of mockingbirds were used only once and for a single

treatment. Due to predation events and data logger malfunction, the number of nests per

treatment varied among treatments: n = 11 for food+, n = 18 for heat+, n = 10 for food+/heat+,

and n = 12 for control.

Only female mockingbirds incubate. Between days four and nine of treatments, we

observed each female for a total of eight hours, distributed in two-hour blocks between sunrise

and 14:00 over four days. During these two-hour blocks, we continuously recorded the time

spent doing the following behaviors: incubating, foraging, preening, being still, panting on the

nest (cooling the eggs) and "other" (singing, territorial defense, flying, etc.). Most behaviors

were mutually exclusive birds could not engage in two simultaneously. Panting and incubation

were exceptions, because incubating birds often panted. In that situation, we recorded the exact

time intervals during which females panted. Females spent all night on the nests, arriving at

sunset and departing at sunrise. Therefore, any differences in incubation among treatments are

due to differences in incubation behavior during the day. Behavioral observation were conducted

on 65 nests (food+ = 16; food+/heat+ = 14; heat+ = 19; control = 16).

On day ten of the incubation period, we captured as many females as possible (food+ = 9

females; food+/heat+ = 8; heat+ = 16; control = 12) and weighed them to the nearest gram.

For each treatment, we recorded the day on which any nest was lost to predation before the

completion of the experiment (ten days). We used two metrics of nest predation for each









treatment: the total number of nests lost to predation and the average daily survival rate. For this

analysis we used 80 nests, 17 in food+, 21 in control, 18 in food+/heat+ and 24 in heat+.

On day ten after sunset, we collected the eggs from all nests to measure treatment effects

on embryonic development. Egg mass was measured to the nearest 0.05g and egg length and

width were measured to the nearest 0.lmm. We opened each egg, removed all membranes,

weighed the embryo to the nearest 0.05g, and recorded the length and width to the nearest

0. mm. We also quantified the number of non-developed embryos, which we define as eggs that

contained minute embryos that were too small to weigh or remove from the yolk without

damage. We measured 111 embryos from 42 nests: 38 embryos from 13 control nests; 27

embryos from 10 food+ nests; 19 embryos from 7 food+/heat+ nests, and 27 embryos from 12

heat+ nests.

In 2006, we collected ectoparasites by the "dust-ruffling" technique (Jackson, 1985;

Walther and Clayton, 1997). Females were lightly dusted with pyrethrin powder, except for the

head. We worked the pyrethrum into the feathers with fingers, waited 5 minutes, and ruffled the

feathers over a tray lined with colored paper, against which the ectoparasites were easily visible.

We placed ectoparasites in micro-centrifuge tubes with 99% ethanol. Because the dust-ruffling

technique works best for lice (Walther and Clayton, 1997), we only quantified the number of

feather lice, which we counted under a stereo microscope. We sampled a total of 28 females; five

from control nests, six from food+ nests, six from food+/heat+ nests, and 11 from heat+ nests.

The temporal pattern of incubation for each nest was obtained from temperature

fluctuations detected by each nest's internal sensor and analyzed following the protocol

suggested by Cooper and Mills (2005). In brief, temperature readings from the data loggers were

converted into a text file, which was then transformed into a sound file, using Rhythm software









(Cooper and Mills, 2005). An algorithm detected all intervals in which temperatures decreased

monotonically and retrieved three quantities for each such interval: duration, total drop in

temperature, and initial rate of temperature decrease. Based on preliminary analyses coupled

with direct observations of when females arrived and left nests, detection of an off-bout (end of

an incubation period) was triggered when nest temperature decreased monotonically for at least 1

min and dropped at least 20C at an initial rate of at least 0.5C/min. Detection of an on-bout

(beginning of an incubation period), was triggered when temperature increased monotonically

for at least 1 min at an initial rate of at least 0.5C/min.

Data on incubation behavior were analyzed with a repeated-measures ANOVA (General

Linear Model procedure of SAS, version 9.1), with food, heat, year, and all two-way interactions

included in the model. Response variables, each analyzed separately, were total minutes of

incubation time during daylight for each of the ten days of a treatment (i.e., sum of all on-bout

times for each day), number of trips from the nest for each day (i.e., total number of off-bouts),

and total duration of trips from the nest for each day. Differences in female and embryo mass

were analyzed with a two-way ANOVA, with mass as a dependent variable, food and heat as

fixed factors and nest as a random factor. The numbers of nests lost to predation in each

treatment were compared with a chi-square test. We also estimated daily predation rates among

categories, using Shaffer's logistic regression model (Shaffer, 2004; SAS, 9.1). For post hoc tests

we used the Tukey-Kramer honestly significant difference (Tukey-Kramer HSD), which is

relatively unlikely to result in a Type 1 error (Hilton and Armstrong, 2006).









CHAPTER 3
RESULTS

Inner nest temperatures were always hotter than ambient temperatures, with differences

fluctuating between 3 and 7C depending on the treatment. By day, when heaters were turned on,

nest temperatures differed significantly among treatments (F 3,407 = 27.37, p < 0.001). Nests in

both heat treatments (heat+ and food+/heat+) had higher temperatures (2-3C; p's < 0.001), than

non-heated treatments (food+ and control). Nest temperatures did not differ significantly among

heat treatments (p's = 0.97). In contrast, daily nest temperatures differed between food+ and

control treatments (p's < 0.007), with higher nest temperatures (0.9C) in food+ treatments.

Incubation time. Females in the four groups spent from 52.2% (heat+) to 64.4% (food+) of

daylight hours incubating. There was no year effect on total daily incubation time (F1,45 = 0.00,

p = 0.98). Food+ and heat+ treatments affected total incubation time, although their influences

were only marginally significant (F 1,45 = 4.1, p = 0.04; F1,45 = 3.9, p = 0.05, food+ and heat+,

respectively). All interaction terms were non-significant. Total incubation time for females over

the entire 10-day period on food+ nests was 12.2% greater than those on heat+ nests (p's < 0.04,

Tukey's; Fig. 1). Total incubation time on control and food+/heat+ was intermediate (56.1-

56.6%, respectively), and not significantly different from food+ or heat+ nests (p's = 0.31 and

0.45, Tukey's, respectively; Fig. 1). The average number of trips off the nest each hour was

significantly affected by heat+ (F 1,45 = 5.56, p = 0.02), with females on heat+ nests averaging

21.9%, 18.8%, and 13.9% more trips per hour than on food+, control, and food+/heat+ nests,

respectively (Fig. 2a). There were marginally significant differences in number of trips per hour

on food+ and heat+ nests (p's = 0.06, Tukey's). Trip length (Fig. 2b) was not significantly

affected by food+ (F1,45 = 2.65, p = 0.11) or heat+ treatments (F1,45 = 2.67, p = 0.11). Females in

the food+ treatment tended to make shorter trips, approximately 21% less than females in the









other treatments, but no pair-wise posthoc comparisons were significant (0.08
Tukey's, Fig. 2b). During incubation, females differed in the percentage of time spent panting

(F3,64 = 4.86, p = 0.04), with females on heat+ and food+/heat+ nests spending 19% and 17%

(respectively) of incubation time panting, compared to 3% of time for females on both food+ and

control nests.

Behaviors: Female behavior off the nest differed among treatments (Fig. 3). Foraging

behavior was significantly influenced by food+ (F1,64 = 148.23, p <0.0001) and not by heat+

(F1,64 = 0.24, p = 0.20). Time spent preening was greatly influenced by additional food (food+;

F1,64 = 60.12, p <0.0001) but not by additional heat (heat+; F1,64 = 0.002, p = 0.967). Time spent

being still was affected by food+ (F, 64 = 4.04, p = 0.04) and not by heat+ (F1,64 = 1.68, p = 0.20).

Time spent on "other" activities was not influenced by either food+ (F1,64 = 2.63, p = 0.11) or

heat+ (F1,64= 0.001, p = 0.976) treatments.

Other measurements: Body mass on the last day of trials (day ten) was not affected either

by food (F1,46 = 0.68,p = 0.42) or heat (F1,46 = 0.97, p = 0.33). The total number of nests lost to

predators did not differ among groups (X20.05 = 0.43, df = 3, p = 0.94 ). Daily nest survival rates

ranged from 97.8% and 98.2% and did not differ among treatments. Frequency of ectoparasites

was very low. We found lice on only two of 45 females that were examined. One was in the

heat+ treatment and the other was from the control group.

Embryo mass was significantly affected by our treatments (Fi, 40 = 6.44, p < 0.001, Fig. 4).

Embryo mass in the heat+ treatment was between 26% and 28% lighter than any other treatment.

Embryo mass was similar among control, food+ and food+/heat+ treatments. There were no

difference in the number of undeveloped embryos among treatments (X20.05 = 5.15, df = 3,p =

0.16).











4600
a

4400


S4200 -
4-1
(D ab

a 4000
C
o 3800 ab

S+ b
3600 -
1- 13
I- i
3400 1l

18
3200 I
Food+ Control Food+/Heat+ Heat+

Treatments

Figure 3-1. Mean incubation times during ten days of the different experimental females.













3.6 -


3.4 -

3.2

o 3.0 -
J--

2 2.8
"4-

S 2.6
I-

2.4

2.2

2.0

11.5


11.0 -


S10.5
C

E 10.0 -


S9.5
4-J
03

ci 9.0


8.5


8.0
Food+ Control Food+/Heat+ Heat+

Treatments


Figure 3-2. Mean number of trips and trip length during ten continuous day of incubation among
treatments.


















a
a








b





Feather care


Foraging


SControl
7:I1 Food +
E7 Food+/Heat+
I Heat+


Being still


100 -



80 -



60 -



40 -



20 -


Behaviors


Figure 3-3. Average female time spent during incubation recesses,
observation among treatments on different behaviors.


throughout eight hours of


120 -


Others













1.7


1.6 -


1.5 -


1.4 -
LO
U/)

E 1.3 -
0

E 1.2-
IiJ
b
1.1


1.0


0.9 ,
Control Food Food/Heat Heat

Treatments


Figure 3-4. Embryo mass among treatments after ten days of continuous incubation.









CHAPTER 4
DISCUSSION

Results showed that both food availability and temperature influence the pattern of

incubation. Increasing food availability enabled females to spend more time on the nest, and

more time in self-maintenance activities when off the nest. Increasing heat caused females to

spend less time on the nest and to make more trips to and from the nest. When both food and

temperature were increased, their effects on incubation time offset each other. Thus our results

provide support for our predictions. Changes in incubation patterns had little effect on fitness.

Embryonic mass was reduced in the heat+ treatment, but this may simply reflect heat stress,

which incubating females sometimes had to offset by panting. None of the other measurement of

fitness (ectoparasite loads, adult mass, nest predation) differed among treatments

Perhaps the reason why temperature only explained 17-47% of the variation in incubation

patterns (Conway and Martin, 2000a) is that the two factors, food and temperature, offset each

other in complex ways that could obscure their effects on incubation behavior. In the remainder

of this section, we first look at how each factor affects incubation separately, and then explore

ways in which the two factors interact.

Incubation Time

Effects of supplement food: As predicted, supplemental food increased time on the nest

(Eikenaar et al., 2003; Zimmerling and Ankney, 2005; Rastogi et al, 2006; Chalfoun and Martin,

2007). Females increased their time on the nest by reducing the average duration of trips off the

nest, rather than by reducing the number of trips. Shorter trips not only assure longer times of

appropriate thermal condition for adequate embryo development, they also reduce the cost of re-

warming eggs, which do not cool down as much during short off bouts (Vleck, 1981 a; Vleck,









198 lb; Tinbergen and Williams, 2002). Shorter trips off the nest were likely made possible by

faster acquisition of energy in food+ territories (see below).

Effects of supplement heat: As predicted by Conway and Martin (2000a), females with

supplemental heat increased the number of trips without increasing the length of these trips. The

result was a reduction in nest attentiveness. Temperatures outside the thermal neutral zone

(region of physical regulation), such as those experienced by our heat+ females on the nest, can

increase adult metabolic rate (McNab, 2002), which would in turn require an increase in food

intake (McWilliams et al.,1999; Dykstra and Karasov, 1992). Moreover, adult thermoregulation

during incubation can be costly and can account for 31% of daily energy expenditure (Piersma

and Morrison, 1994). Thus, foraging activity might be predicted to increase among birds that

incubate in high ambient temperatures (Bergstrom, 1989; Conway and Martin, 2000a; Conway

and Martin, 2000b). We did not, however, find that females increased their foraging time in

supplemental heat treatments. The lack of increase in food intake at high temperatures suggests

that behavioral responses maybe more important in regulating body temperatures at high

temperatures, above the thermal neutral zone (Ricklefs, 1987). Alternatively, we may not have

increased temperatures enough to cause significant energetic stress in the adults.

Interactions food and temperature: As we predicted, females on control and food+/heat+

territories spent an intermediate amount of time on the nest, not significantly different than either

heat+ or food+ females. These results suggest that increases in food availability compensate for

the high energy expenditure of cooling eggs in hot conditions, by allowing females to reduce the

number of trips off the nest and thereby better regulating egg temperature. This difference in

incubation patterns may explain why embryo mass was significantly reduced in heat+ treatments,









but not in food+/heat+ treatments. We do not yet know how the extra food may enable females

to provide better conditions for embryonic development.

Our results may shed light on why neither food nor temperature explained much of the

variance in incubation patterns in Conway and Martin's (2000b) interspecific analysis. Birds

living in food-rich environments may be able to compensate for temperature-induced stresses

(McWilliams, et al., 1999; Dykstra and Karasov, 1992). Conversely, birds living in colder

climates may benefit more from increasing temperatures than did our mockingbirds, which breed

mainly in warmer, south temperature climates. Thus, the interactions of food and temperature

can offset each other and likely vary greatly among environments that differ in ambient

temperature and food availability.

Behaviors during Recess from Incubation

The time freed from foraging by food+ females was allocated to maintenance behaviors.

Maintenance behaviors have been shown to influence nest survival and fitness (Cucco and

Malacarne, 1997; Nagy and Holmes, 2005; Rastogi et al., 2006), but we found no evidence for

reduced nest predation or adult condition. The lack of difference in body mass suggests that

females with supplemental food did not store extra energy; rather they invested it in the current

nesting attempt. Although our urban mockingbird population had few ectoparasites, reduction

and removal of parasites by preening could result in higher fitness (Casida et al., 1995).

Time allocated to other behaviors (e.g., territorial defense, intra-specific interactions) was

not consistent among treatments. Consequently, these behaviors were not influenced by either

food+ or heat+. One possible explanation for this can be the lack of direct effects of these

behaviors on current reproduction and adult survival. Cucco and Malacarne (1997) showed that

individuals in territories with extra, supplemented food increased the time allocated to nest









defense. However, female Mockingbirds with high food availability did not increase territorial

defense, probably because in this species, males do most territorial defense, but do not incubate.

Nest predation Despite significant differences in trips per hour among the four treatment

groups, we found no differences in the number of nests lost to predators or in the average

survival time of eggs in nests. This result contradicts those of several previous studies that found

a positive association between trip number and nest predation (Martin et al., 2000; Muchai and

Plessis, 2005; Rastrogi et al., 2006). However, this association is clearly not universal; our

results agree with those of Hans-Christian (2005). Possibly, a 20% increase in trips per hour may

not be enough to significantly affect nest predation rates. Alternatively, differences in nest

predation observed among studies may be driven by factors correlated with visit frequency but

not directly examined in any of the studies. In mockingbirds, nest predation rates may be

constrained by the behavior of males, which actively defend nests against predators (Derrickson

and Breitwisch, 1992).

Conclusions: For birds, incubation may be costly because eggs develop externally and

often in environments with large fluctuations in temperature. To keep temperatures in the

optimal range for development, birds can vary the frequency and duration of incubating sessions

and modify their behavior while incubating and while off the nest. But, this involves life-history

tradeoffs. Increasing the duration and frequency of incubation sessions requires less time spent

on other fitness-enhancing activities such as foraging and self-maintenance. Consequently,

temperature and food have long been hypothesized to be the primary constraints on the ability of

birds to provide optimal conditions for incubating eggs. Several recent papers (reviewed in

Conway and Martin, 2000a) have argued that temperature is a more important determinant of

incubation behavior than food availability. Our results, however, point to the importance of both









food and ambient temperature. Increasing food availability enabled birds to spend more time

keeping eggs at optimal temperatures and more time in self-maintenance activities, which may

substantially reduce the costs of incubating for the adults themselves. Increasing temperatures,

on the other hand, mainly influenced the frequency of visits to the nest except at very high

temperatures when the birds were apparently forced to spend energy cooling their eggs to avoid

potentially lethal effects. Thus, our experiment shows that food and temperature both affect

avian incubation behavior, but that different tradeoffs apply to each environmental factor.









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availability on incubation attendance and hatching asynchrony in the Australian reed
warbler Acrocephalus australis. Journal of avian biology 34:419-427.

Franks 1967, The responses of incubating Ringed Turtle Dove (Streptopelza rzsorza) to
manipulate egg temperatures. Condor 69:268-276.

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hypoleuca). Auk 113:249-253.

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size. Biological Review 73:293-304.

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Behaviour, Environment, and Evolution (Deeming, DC, ed). Oxford University Press, New
York; 299-313.

Turner JS, 2002. Maintenance of egg temperature. In: Avian incubation Behaviour,
Environment, and Evolution (Deeming, DC, ed). Oxford University Press, New York; 119-
142.

Vleck CM, 1981 a. Energetic cost of incubation in the Zebra finch. Condor 83:229-237.

Vleck CM, 1981b. Hummingbird incubation- female attentiveness and egg temperature.
Oecologia 51:199-205.

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loads of live birds. Journal of Field Ornithology 68:509-518.









Weathers WW, and Sullivan KA, 1989. Nest attentiveness and egg temperature in the yellow-eye
junco. Condor 91:628-633.

Weeden JS, 1966. Diurnal rhythm of attentiveness of incubation female tree swallows (Spizella
arborca) at a northern latitude. Auk 83:368-388.

Wiebe KL, and Martin K, 2000. The use of incubation behavior to adjust avian reproductive cost
after egg laying. Behavioral Ecology and Sociobiology 48:463-470.

Williams JB, 1993. Energetics of incubation in free-living Orange-breasted sunbirds in South
Africa. Condor 95:115-126.

Williams JB, 1996. Energetics of avian incubation. In: avian energetic and nutrition ecology
(Carey C, ed). New York: Chapman & Hall; 375-416.

Zebra E, and Morton ML, 1983. Dynamics of incubation in Mt. White-crowned sparrows.
Condor 85:1-11.

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Blackbirds nesting at lagoons and pounds in eastern Ontario. Wilson Bulletin 117:280-290.









BIOGRAPHICAL SKETCH

Gustavo Adolfo Londofio was born in 1976 in Cali, Colombia. The older of two

children, he grew up mostly in Cali, Colombia, graduating from Gimnasio la Colina High School

in 1993. After his high school graduation, he spent 1 year in Morton, Illinois, as an exchange

student. In fall 1994 he enrolled the Universidad de los Andes, Bogota, Colombia, where he

started his biology bachelor's degree. During his undergrad career Gustavo was involved in

many field research programs that principally involved birds. After finishing his B.S. in biology

in 2000, Gustavo was involved in bird field projects in different countries, Canada, Costa Rica,

Peri and Colombia. In 2003 he participates in the Organization for Tropical Ecology field course

in ecology and conservation in Costa Rica. Gustavo work with Wildlife Conservation Society

Colombia program from 2002-2004, gathering data to develop conservation strategies for some

endanger Andean birds in Colombia that affect incubation behavior of the Northern Mockingbird.

Upon completion of his master's program, Gustavo will begin working toward his Ph.D.

At the Zoology Department, University of Florida under the advice of Douglas Levey and Scott

Robinson where he will study factors that affect incubation behavior of high elevation tropical

birds.





PAGE 1

1 EFFECTS OF TEMPERATURE AND F OOD ON AVIAN INCUBATION BEHAVIOR By GUSTAVO ADOLFO LONDOO A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2007

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2 2007 Gustavo Adolfo Londoo

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3 ACKNOWLEDGMENTS I thank S. Robinson and D. Levey for their suppo rt and advice. I also thank J. Gillooly for suggestions to improve earlier versions of this thesis. Field work data collection was possible thanks to the help of J. Ungvari-Martin, M. R. Hiersoux, A. Savage, M. Phillips, and D. DeSantis. Financial support was provided by the Ordway laboratory, the Zoology Department, Animal Behavior Society, and Brian Riewald and John Paul Olowo Memorial Fund research grants.

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4 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................3 LIST OF FIGURES................................................................................................................ .........5 ABSTRACT....................................................................................................................... ..............6 CHAPTER 1 INTRODUCTION................................................................................................................. ...7 2 STUDY SITE AND METHODS............................................................................................10 3 RESULTS...................................................................................................................... .........15 Incubation Time......................................................................................................................15 Behaviors...................................................................................................................... ..........16 Other M easurements............................................................................................................. ..16 4 DISCUSSION................................................................................................................... ......21 Incubation Time................................................................................................................ ......21 Effects of Supplement Food.............................................................................................21 Effects of Supplement Heat.............................................................................................22 Interactions Food and Temperature.................................................................................22 Behaviors during Recess from Incubation..............................................................................23 Nest Predation..................................................................................................................24 Conclusions.................................................................................................................... .24 REFERENCES..................................................................................................................... .........26 BIOGRAPHICAL SKETCH.........................................................................................................30

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5 LIST OF FIGURES Figure page 3-1 Mean incubation times during ten days of the different experimental females.................17 3-2 Mean number of trips and trip length during ten continuous day of incubation among treatments..................................................................................................................... ......18 3-3 Average female time spent during inc ubation recesses, thro ughout eight hours of observation among treatments on different behaviors.......................................................19 3-4 Embryo mass among treatments after te n days of continuous incubation.........................20

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6 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science EFFECTS OF TEMPERATURE AND F OOD ON AVIAN INCUBATION BEHAVIOR By Gustavo Adolfo Londoo August 2007 Chair: Scott Robinson Cochair: Douglas Levey Major: Zoology Avian incubation behavior is thought to be in fluenced mainly by ambient temperature and food availability. Field studies, however, have generated contradictory results and no general agreement about the relative impor tance of food and temperature influence and on how different components of incubation behavior are affected by each. Therefore, we experimentally increased both food availability and ambient temperature during incubation in the Northern Mockingbird ( Mimus polyglottos ). Our results demonstrated that bot h food availability and temperature influence incubation behavior. Increasing food ava ilability enabled females to spend more time on the nest and in self-maintenance activities when off the nest. Increasing heat caused females to spend less time on the nest and to make more trips to and from the nest. When both food and temperature were increased, their effects on incuba tion time offset each other. These changes in incubation patterns had little eff ect on fitness, although embryo mass was lowest in the treatment in which only heat was increased, suggesting that heat may stress embryos, but not when extra food is also provided. Perhaps the reason why prev ious studies present co ntradictory results is because food and temperature offset each other in complex ways that could obscure their effects on incubation behavior.

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7 CHAPTER 1 INTRODUCTION Embryonic development in birds is unique amo ng vertebrates because it typically requires direct transfer of body heat from incuba ting adults (Deeming, 2002a; Turner, 2002). The energetic costs of incubation have been genera lly overlooked because they are thought to be far lower than the more obvious costs of feed ing young. Recent studies, however, suggest that incubation is energetically costly (Williams, 1996; Thoms on et al., 1998; Tinbergen and Williams, 2002) and that incubati on behavior influences the proba bility of predators finding the nest (Martin et al., 2000; Muchai and Plessis, 2005; Rastogi et al., 2006). Because time and energy invested in incubation means less time a nd energy for energy intake (foraging) and self maintenance, incubating birds face a trade-off between parental and self care (Williams, 1996; Tinbergen and Williams, 2002; Turner, 2002). Elucidating this life history trade-off requires understandi ng what influences incubation rhythms (Martin, 2004), defined as the length and temporal patte rn of incubation bouts. Two factors that play important roles in incubation rhythms ar e ambient temperature and food availability (Skutch, 1962; Lack, 1968; Grant, 1982; Martin, 1987; Weathe rs and Sullivan, 1989; Conway and Martin, 2000a; Conway and Mart in, 2000b; Deeming, 2002b; Ei kenaar et al., 2003; Lloyd and Martin, 2004; Martin, 2004; Na gy and Holmes, 2005; Zimmerling and Ankney, 2005). Ambient temperature influences energy expenditure during in cubation and embryonic growth during recesses from incubation (Baer nand, 1959; Weeden, 1966; Drent, 1970; Vleck, 1981a; Zebra and Morton, 1983; Reid et al., 1999; Conway and Martin, 2000a; Tinbergen and Williams, 2002; Cresswell et al., 2004). In contrast food availability contro ls the rate of energy acquisition and hence the times off the nest a nd the time available for other self-maintenance activities (Skutch, 1962; Martin, 1987; Weathers and Sullivan, 1989; Nilsson, 1994; Sanz, 1996;

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8 Cucco and Malacarne, 1997; Eikenaar et al., 20 03; Zimmerling and Ankne y, 2005; Rastogi et al., 2006; Chalfoun and Martin, 2007). Conway and Ma rtin (2000a) conclu ded that incubation rhythm depended on ambient temperature rather th an food. The effects of temperature, however, were non-linear and explained only a small proportion of varia tion in incubation rhythm among species. The same authors proposed that food does not explain variation in incubation rhythm, at least among species (Conway a nd Martin, 2000b). Within speci es, however, food can affect incubation rhythm (Conway and Martin, 2000a; Zimmerling and Ankney, 2005; Rastogi et al., 2006). Therefore, there are contradictory result s and no general agreem ent about the relative contributions of food and temperat ure on avian incubation behavior. We suggest that much of the confusion about the roles of food and temperature stems from the assumption that these two factors act independ ently or the belief that one factor overwhelms the effects of the other. Yet the relative importance and potential in teraction of food and temperature are impossible to judge in the abse nce of experiments that manipulate both factors simultaneously (Martin, 1987; Conway and Ma rtin, 2000a; Wiebe and Martin, 2000; Martin, 2004). We are not aware of any studies designed in such a way. Also, most studies of incubation focus on quantifying when birds are on or off the nest and generally do not attempt to describe behaviors when off the nest. Because behaviors th at occur off the nest likely influence behaviors on the nest, both should be consid ered part of incubation behavi or -both can have a strong influence on nest survival and adult fitne ss (Franks, 1967; Vleck, 1981a; Davis et al., 1984; Cucco and Malacarne, 1997; Nagy and Ho lmes, 2005; Zimmerling and Ankney, 2005). Our primary objective was to evaluate expe rimentally the interaction and relative importance of food availability and temperat ure on avian behavior during incubation. We hypothesized that both food and temperature a ffect incubation behavior. We tested three

PAGE 9

9 predictions: Prediction 1: Females on territories with high food availability will spend more time on the nest and more time doing other pote ntially fitness-enhanci ng behaviors such as preening or defending the nest because hunger levels and foraging times will be reduced. Prediction 2: Females on nests in hotter microclimates will decrease time on nest and increase the total number of trips to the nest per day because metabolic needs increase at high temperatures, as predicted by Conway and Mart in (2000a). Furthermore, females in hotter microclimates, when on the nest, should spend more time regulating ne st temperature through behavioral responses such as panting or e gg shading (Franks, 1967; Vleck, 1981a; Davis et al., 1984). Prediction 3: Females that experience both hot microclimates and high food abundance should spend an intermediate amount of time on the nest. The reasoning behind this last prediction is that food an d heat influence time on the nest in opposite directions (predictions 1 and 2), with food increasing time on the nest (Zimmerling and Ankney, 2005; Rastogi et al., 2006) and heat (high temperatures) increasing on and off-bouts, wh ich decreases time on the nest (Conway and Martin, 2000a). We tested these predictions by experimenta lly manipulating food availability and nest microclimate of Northern Mockingbirds ( Mimus polyglottos ), a species in which only females incubate and males do not provide food to incubating females.

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10 CHAPTER 2 STUDY SITE AND METHODS This study was conducted between April 1 and July 15 in 2005 and 2006 on the University of Florida campus in Gainesville, Florida (N29 38' 267"; W 082 21' 984"). The campus has ideal mockingbird habitat: large expanses of mo wed grass for foraging and scattered shrubs for nesting. The study area was divided in six sections and, once per week, all shrubs and trees within each section were searched for nests. Each ne w nest, either under construction or with an incomplete clutch (1-2 eggs), was randomly assigne d to one of four experimental treatments in a 2 x 2 factorial design: Food increase (food+), heat increase (heat+), food and heat increase (food+/heat+), and neither food nor heat increase (control). Food+ nests had a feeder placed within 2 to 5 m. Feeders consisted of a plastic food storage container mounted 1.5 m above the ground on a PVC pipe. They were placed when ne sts were first found and supplied daily with mealworms ( Tenibrio molitor ). Based on preliminary observations of the number of mealworms consumed by a pair of mockingbirds, we placed 160 mealworms (approximately 17g) in each feeder every day. Mealworms have an energetic value of 11.6 kJ/g and birds can metabolize a minimum of 71% of the energy available in an average insect (Bell 1990 ); our provision of 160 mealworms therefore would provide the mockingb ird pair with about 5.83 kJ/h of additional energy. Female mockingbirds consumed 7.5.68 (se) mealworms per hour.We calculated the BMR (basal metabolic rate) for an insectivor ous bird of 48g (eq. 6; McNab, 2005) to be 1.83 kJ/h. Thus, assuming that energetic requirements during incubation are three times higher than the BMR (Williams, 1993; Piersma and Morrison, 1994) we estimated that female mockingbirds spent 5.49 Kj/h during the incubation period. So, mealworms provided approximately 53% of the daily energy expended by th e female during incubation.

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11 Feeders were used exclusively by the pair of mockingbirds at the near est nest, except in a few cases when juveniles from a pairs previous cl utch also used the feeder. In those cases, an extra 8g of mealworms were placed in the feeder. Because high temperatures can kill mealworms in the feeders and because mockingbirds usually do not eat dead mealworms, half of the mealworms were placed in the feeders before sunrise and the remaining half were placed in the early afternoon. Typically, most or all of the mealworms had been consumed by the time more were added. Heat+ nests received an 18 watt bulb in a 47 x 32.2mm (length x diameter) cylindrical aluminum tube on the day the third egg was lai d, when the likelihood of nest abandonment was low. The bulb and cylinder were placed direc tly under the nest, touching nest material, approximately 30mm from the eggs. After the cl utch was complete and incubation had started, the bulb was turned on shortly before sunrise (0600) and remained on until the battery was drained, approximately 8 hours later. When th e bulb was on, the nest chamber experienced a temperature of approximately 35oC, which corresponds to the daytime high temperature at the study site in late summer, when most mocki ngbirds stop breeding. Ambient temperature ranged from 17.0 to 37.1 oC (average: 26.6; Std. Dev. = 1.2) during the study period. Nests that did not receive a heater (food+, and contro l nests) received a sham heat er. Food+/Heat+ nests received both a feeder and a heater; co ntrol nests received neither. All nests had two thermal sensors (39.5x7.1mm), one internal and one external, connected to a H8 4-Channel Hobo data logger (Onset Co mputer Corporation). Sensors were placed in nests the day the third egg was la id and recorded temperature every minute. The internal sensor was attached to the nest wall just above the eggs. It provided two types of information: incubation temperature and the time at which the in cubating bird left or returned to the next, as

PAGE 12

12 detected by rapid temperatur e shifts of at least 1.5oC (see below). The external sensor was attached to the outside nest wall at the same hei ght as the internal sensor and shielded from the heater. It provided data on ambient temperatur e in the immediate vicinity of the nest. All treatments lasted ten days, when all eggs were collected for examination of embryo development (see below). All nesting pairs of mo ckingbirds were used only once and for a single treatment. Due to predation events and data logger malfunction, the number of nests per treatment varied among treatments: n = 11 for food+, n = 18 for heat+, n = 10 for food+/heat+, and n = 12 for control. Only female mockingbirds incubate. Between days four and nine of treatments, we observed each female for a total of eight hours, distributed in two-hour blocks between sunrise and 14:00 over four days. During these two-hou r blocks, we continuously recorded the time spent doing the following behaviors: incubating, foraging, preening, being still, panting on the nest (cooling the eggs) and oth er (singing, territorial defense, flying, etc.). Most behaviors were mutually exclusive birds could not enga ge in two simultaneously. Panting and incubation were exceptions, because incubating birds often pant ed. In that situation, we recorded the exact time intervals during which females panted. Fema les spent all night on th e nests, arriving at sunset and departing at sunris e. Therefore, any differences in incubation among treatments are due to differences in incubation behavior durin g the day. Behavioral obs ervation were conducted on 65 nests (food+ = 16; food+/heat+ = 14; heat+ = 19; control = 16). On day ten of the incubation period, we cap tured as many females as possible (food+ = 9 females; food+/heat+ = 8; heat+ = 16; control = 12) and weighed them to the nearest gram. For each treatment, we recorded the day on which any nest was lost to predation before the completion of the experiment (ten days). We used two metrics of nest predation for each

PAGE 13

13 treatment: the total number of nests lost to predati on and the average daily su rvival rate. For this analysis we used 80 nests, 17 in food+, 21 in control, 18 in food+/heat+ and 24 in heat+. On day ten after sunset, we collected the eggs from all nests to measure treatment effects on embryonic development. Egg mass was meas ured to the nearest 0.05g and egg length and width were measured to the nearest 0.1mm. We opened each egg, removed all membranes, weighed the embryo to the nearest 0.05g, and reco rded the length and width to the nearest 0.1mm. We also quantified the num ber of non-developed embryos, which we define as eggs that contained minute embryos that were too small to weigh or remove from the yolk without damage. We measured 111 embryos from 42 ne sts: 38 embryos from 13 control nests; 27 embryos from 10 food+ nests; 19 embryos from 7 food+/heat+ nests, and 27 embryos from 12 heat+ nests. In 2006, we collected ectoparasites by th e dust-ruffling technique (Jackson, 1985; Walther and Clayton, 1997). Females were lightly dusted with pyrethrin powder, except for the head. We worked the pyrethrum into the feathers with fingers, waited 5 minutes, and ruffled the feathers over a tray lined with colored paper, against which the ectoparasites were easily visible. We placed ectoparasites in micro-centrifuge tu bes with 99% ethanol. Because the dust-ruffling technique works best for lice (Walther and Cl ayton, 1997), we only quant ified the number of feather lice, which we counted under a stereo micr oscope. We sampled a total of 28 females; five from control nests, six from food+ nests, six from food+/heat+ nests, and 11 from heat+ nests. The temporal pattern of incubation for each nest was obtained from temperature fluctuations detected by each nests internal sensor and analyzed following the protocol suggested by Cooper and Mills (2005). In brief, te mperature readings from the data loggers were converted into a text file, which was then tran sformed into a sound file, using Rhythm software

PAGE 14

14 (Cooper and Mills, 2005). An algorithm detected all intervals in which temperatures decreased monotonically and retrieve d three quantities for each such interval: duration, total drop in temperature, and initial rate of temperature decrease. Based on preliminary analyses coupled with direct observations of when females arrived and left nests, detection of an off-bout (end of an incubation period) was triggered when nest te mperature decreased monotonically for at least 1 min and dropped at least 2oC at an initial rate of at least 0.5oC/min. Detection of an on-bout (beginning of an incubation period), was trigge red when temperature increased monotonically for at least 1 min at an initial rate of at least 0.5oC/min. Data on incubation behavior were analyzed with a repeated-measures ANOVA (General Linear Model procedure of SAS, version 9.1), with food, heat, year, and a ll two-way interactions included in the model. Response variables, each analyzed separately, were total minutes of incubation time during daylight for each of the te n days of a treatment (i.e., sum of all on-bout times for each day), number of trips from the ne st for each day (i.e., total number of off-bouts), and total duration of trips from the nest for each day. Differences in female and embryo mass were analyzed with a two-way ANOVA, with ma ss as a dependent variable, food and heat as fixed factors and nest as a ra ndom factor. The numbers of nest s lost to predation in each treatment were compared with a chi-square test We also estimated daily predation rates among categories, using Shaffers logistic regression model (Shaffer, 2004; SAS, 9.1). For post hoc tests we used the Tukey-Kramer honestly significan t difference (Tukey-Kramer HSD), which is relatively unlikely to result in a Type 1 error (Hilton and Armstrong, 2006).

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15 CHAPTER 3 RESULTS Inner nest temperatures were always hotter than ambient temperatures, with differences fluctuating between 3 and 7C de pending on the treatment. By day, when heaters were turned on, nest temperatures differed si gnificantly among treatments (F 3,407 = 27.37, p < 0.001). Nests in both heat treatments (heat+ and food+/h eat+) had higher temperatures (2-3C; p s < 0.001), than non-heated treatments (food+ and control). Nest temperatures did not differ significantly among heat treatments ( p s = 0.97). In contrast, daily nest te mperatures differed between food+ and control treatments ( p s < 0.007), with higher nest temperatur es (0.9C) in food+ treatments. Incubation time Females in the four groups spent fr om 52.2% (heat+) to 64.4% (food+) of daylight hours incubating. There was no year effect on total daily incubation time (F1,45 = 0.00, p = 0.98). Food+ and heat+ treatments affected total incubation time, a lthough their influences were only marginally significant (F 1,45 = 4.1, p = 0.04; F1,45 = 3.9, p = 0.05, food+ and heat+, respectively). All interaction terms were non-sign ificant. Total incubati on time for females over the entire 10-day period on food+ nests was 12.2 % greater than those on heat+ nests (ps < 0.04, Tukeys; Fig. 1). Total incubation time on c ontrol and food+/heat+ was intermediate (56.156.6%, respectively), and not significantly different from fo od+ or heat+ nests (ps = 0.31 and 0.45, Tukeys, respectively; Fig. 1). The average nu mber of trips off the nest each hour was significantly affected by heat+ (F 1,45 = 5.56, p = 0.02), with females on heat+ nests averaging 21.9%, 18.8%, and 13.9% more trips per hour than on food+, contro l, and food+/heat+ nests, respectively (Fig. 2a). There were marginally significant differen ces in number of trips per hour on food+ and heat+ nests (ps = 0.06, Tukeys). Trip length (Fig. 2b) was not significantly affected by food+ (F1,45 = 2.65, p = 0.11) or heat+ treatments (F1,45 = 2.67, p = 0.11). Females in the food+ treatment tended to make shorter trip s, approximately 21% less than females in the

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16 other treatments, but no pa ir-wise posthoc comparisons were significant (0.08 < p s < 0.15 Tukeys, Fig. 2b). During incubation, females di ffered in the percentage of time spent panting (F3,64 = 4.86, p = 0.04), with females on heat+ a nd food+/heat+ nests spending 19% and 17% (respectively) of incubation time panting, compared to 3% of time for females on both food+ and control nests. Behaviors: Female behavior off the nest differed among treatments (Fig. 3). Foraging behavior was significantly influenced by food+ (F1,64 = 148.23, p <0.0001) and not by heat+ (F1,64 = 0.24, p = 0.20). Time spent preening was greatly influenced by additional food (food+; F1,64 = 60.12, p <0.0001) but not by additional heat (heat+; F1,64 = 0.002, p = 0.967). Time spent being still was affected by food+ (F1, 64 = 4.04, p = 0.04) and not by heat+ (F1,64 = 1.68, p = 0.20). Time spent on other activities was not influenced by either food+ (F1,64 = 2.63, p = 0.11) or heat+ (F1,64 = 0.001, p = 0.976) treatments. Other measurements: Body mass on the last day of trials (d ay ten) was not affected either by food (F1,46 = 0.68, p = 0.42) or heat (F1,46 = 0.97, p = 0.33). The total number of nests lost to predators did not differ among groups ( X2 0.05 = 0.43, df = 3, p = 0.94 ). Daily nest survival rates ranged from 97.8% and 98.2% and did not differ among treatments. Frequency of ectoparasites was very low. We found lice on only two of 45 females that were examined. One was in the heat+ treatment and the othe r was from the control group. Embryo mass was significantly affected by our treatments (F1, 40 = 6.44, p < 0.001, Fig. 4). Embryo mass in the heat+ treatmen t was between 26% and 28% lighter than any other treatment. Embryo mass was similar among control, food+ and food+/heat+ treatments. There were no difference in the number of undeveloped embryos among treatments ( X2 0.05 = 5.15, df = 3, p = 0.16).

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17 Figure 3-1. Mean incubation times during ten days of the different experimental females.

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18 Figure 3-2. Mean number of trip s and trip length during ten c ontinuous day of incubation among treatments.

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19 Figure 3-3. Average female time spent during in cubation recesses, thro ughout eight hours of observation among treatments on different behaviors.

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20 Figure 3-4. Embryo mass among treatments afte r ten days of continuous incubation.

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21 CHAPTER 4 DISCUSSION Results showed that both food availability and temperature influence the pattern of incubation. Increasing food availability enabled females to spend more time on the nest, and more time in self-maintenance activities when of f the nest. Increasing heat caused females to spend less time on the nest and to make more trips to and from the nest. When both food and temperature were increased, their effects on incuba tion time offset each other. Thus our results provide support for our predictions Changes in incubation patterns ha d little effect on fitness. Embryonic mass was reduced in the heat+ treatment, but this may simply reflect heat stress, which incubating females sometimes had to offset by panting. None of the other measurement of fitness (ectoparasite loads, adult mass, nest predation) differed among treatments Perhaps the reason why temperature only explai ned 17-47% of the variation in incubation patterns (Conway and Martin, 2000a) is that the tw o factors, food and temperature, offset each other in complex ways that coul d obscure their effect s on incubation behavior. In the remainder of this section, we first look at how each factor affects incuba tion separately, and then explore ways in which the two factors interact. Incubation Time Effects of supplement food: As predicted, supplemental food increased time on the nest (Eikenaar et al., 2003; Zimmerling and Ankney, 2005; Rastogi et al, 2006; Chalfoun and Martin, 2007). Females increased their time on the nest by reducing the average duration of trips off the nest, rather than by reducing the number of trip s. Shorter trips not only assure longer times of appropriate thermal condition for adequate embryo de velopment, they also reduce the cost of rewarming eggs, which do not cool down as mu ch during short off bout s (Vleck, 1981a; Vleck,

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22 1981b; Tinbergen and Williams, 2002). Shorter trip s off the nest were likely made possible by faster acquisition of energy in food+ territories (see below). Effects of supplement heat: As predicted by Conway and Martin (2000a), females with supplemental heat increased the num ber of trips without increasing the length of these trips. The result was a reduction in nest attentiveness. Temperatures outside the thermal neutral zone (region of physical regulation), such as those ex perienced by our heat+ females on the nest, can increase adult metabolic rate (McNab, 2002), which would in turn require an increase in food intake (McWilliams et al.,1999; Dykstra and Ka rasov, 1992). Moreover, adult thermoregulation during incubation can be costly and can account for 31% of daily energy expenditure (Piersma and Morrison, 1994). Thus, foraging activity might be predicted to increase among birds that incubate in high ambient temperatures (Ber gstrom, 1989; Conway and Martin, 2000a; Conway and Martin, 2000b). We did not, however, find that females increased their foraging time in supplemental heat treatments. The lack of increas e in food intake at hi gh temperatures suggests that behavioral responses maybe more importa nt in regulating body temperatures at high temperatures, above the thermal neutral zone (R icklefs, 1987). Alternativ ely, we may not have increased temperatures enough to cause signi ficant energetic stre ss in the adults. Interactions food and temperature: As we predicted, females on control and food+/heat+ territories spent an intermediate amount of time on the nest, not signi ficantly different than either heat+ or food+ females. These results suggest that increases in food availability compensate for the high energy expenditure of cooling eggs in hot conditions, by allowing females to reduce the number of trips off the nest and thereby better regulating egg temperature. This difference in incubation patterns may explain why embryo mass wa s significantly reduced in heat+ treatments,

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23 but not in food+/heat+ treatments. We do not yet know how the extra food may enable females to provide better conditions for embryonic development. Our results may shed light on why neither f ood nor temperature explained much of the variance in incubation patterns in Conway and Martins (2000b) interspecific analysis. Birds living in food-rich environments may be able to compensate for temperature-induced stresses (McWilliams, et al., 1999; Dykstra and Karas ov, 1992). Conversely, birds living in colder climates may benefit more from increasing temper atures than did our mockingbirds, which breed mainly in warmer, south temperature climates. Thus, the interactions of food and temperature can offset each other and likely vary greatly among environments that differ in ambient temperature and food availability. Behaviors during Recess from Incubation The time freed from foraging by food+ females was allocated to maintenance behaviors. Maintenance behaviors have been shown to infl uence nest survival and fitness (Cucco and Malacarne, 1997; Nagy and Holmes, 2005; Rastogi et al., 2006), but we found no evidence for reduced nest predation or adu lt condition. The lack of difference in body mass suggests that females with supplemental food did not store extra energy; rather they inve sted it in the current nesting attempt. Although our urban mockingbird population ha d few ectoparasites, reduction and removal of parasites by preening could re sult in higher fitness (Casida et al., 1995). Time allocated to other behavi ors (e.g., territoral defense, in tra-specific in teractions) was not consistent among treatments. Consequently, th ese behaviors were not influenced by either food+ or heat+. One possible explanation for this can be the lack of di rect effects of these behaviors on current reproduction and adult surv ival. Cucco and Malacarne (1997) showed that individuals in territories with extra, supplemented food increa sed the time allocated to nest

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24 defense. However, female Mockingbirds with hi gh food availability did not increase territorial defense, probably because in this species, males do most territorial defense, but do not incubate. Nest predation Despite significant differences in trip s per hour among the four treatment groups, we found no differences in the number of nests lost to predator s or in the average survival time of eggs in nests. This result cont radicts those of several pr evious studies that found a positive association between tr ip number and nest predation (Martin et al., 2000; Muchai and Plessis, 2005; Rastrogi et al., 2006). However, this associatio n is clearly not universal; our results agree with those of Hans-Christian (2005 ). Possibly, a 20% increase in trips per hour may not be enough to significantly a ffect nest predation rates. Alte rnatively, differences in nest predation observed among studies may be driven by factors correlated with visit frequency but not directly examined in any of the studies. In mockingbirds, nest predation rates may be constrained by the behavior of males, which act ively defend nests against predators (Derrickson and Breitwisch, 1992). Conclusions: For birds, incubation may be costly because eggs develop externally and often in environments with large fluctuations in temperature. To keep temperatures in the optimal range for development, birds can vary the frequency and duratio n of incubating sessions and modify their behavior while incubating and while off the nest. But, this involves life-history tradeoffs. Increasing the duration and frequency of incubation sessi ons requires less time spent on other fitness-enhancing activ ities such as foraging and se lf-maintenance. Consequently, temperature and food have long b een hypothesized to be the primary constraints on the ability of birds to provide optimal conditions for incuba ting eggs. Several recent papers (reviewed in Conway and Martin, 2000a) have argued that te mperature is a more important determinant of incubation behavior than food availability. Our results, however, point to the importance of both

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25 food and ambient temperature. In creasing food availability enab led birds to spend more time keeping eggs at optimal temperatures and more time in self-maintenance activities, which may substantially reduce the costs of incubating for the adults them selves. Increasing temperatures, on the other hand, mainly influenced the frequenc y of visits to the nest except at very high temperatures when the birds were apparently forced to spend energy cooling their eggs to avoid potentially lethal effects. Thus, our experime nt shows that food and temperature both affect avian incubation behavior, but that different tradeoffs apply to each environmental factor.

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26 REFERENCES Baernand GP, 1959. The ethological analysis of incubation behavior. Ibis 101:357-368. Bell GP, 1990. Birds and mammals on an insect diet : a primer on diet composition analysis in relation to ecological energetics Studies in Avian Biology 13:416. Bergstrom PW, 1989. Incubation temperatures of Wilsons Polvers and Killdeers. Condor 91:634-641. Casida JE, Clayton DH, and Thompkins DM, 1995. Comparative effects of mites and lice on the reproductive success of rock dove ( Columba livia ). Parasitol 110:195-206. Chalfoun AD, and Martin TE, 2007. Latitudinal varia tion in avian incubation attentiveness and a test of the food limitation hypothesi s. Animal Behaviour 73:579-585. Conway CJ, and Martin TE, 2000a. Effects of ambient temperature on avian incubation behavior. Behavior al Ecology 11:178-188. Conway CJ, and Martin TE, 2000b. Evolution of passerine incubation behavior: influence of food, temperature, and nest predation. Evolution 54:670-685. Cooper CB, and Miles H, 2005. New software fo r quantifying incubation behavior from timeseries recordings. Journal Field of Ornithology 76:352. Cresswell WS, Holt JM, Reid DP, Withfield RJ Mellanby, Norton D, and Waldron S, 2004. The energetic costs of egg heating constraint incubation attendan ce but do not determine daily energy expenditure in the pectoral sandpiper. Behavior al Ecology 15:498-507. Cucco M, and Malacarne G, 1997. The effects of food supplementation on time budget and body condition in the Black Redstart Phoenicurus ochruros Ardea 85:211-221. Davis SD, Williams JB, Adams WJ, and Brown SL, 1984. The effects of egg temperature on attentiveness in the Beldings savannah sparrow. Auk 101:556-566. Deeming DC, 2002a. Embryonic development and u tilization of egg components. In: Avian incubation Behaviour, Environmen t, and Evolution (Deeming, DC, ed). Oxford University Press, New York; 43-53. Deeming DC, 2002b. Behavioral patterns during incubation. In: Avian incubation Behaviour, Environment, and Evolution (Deeming, DC, ed). Oxford University Press, New York; 6386. Derrickson KC, and Breitwisch R, 1992.Northern mockingbird. In: the birds of North America, No. 7 (Poole A, Stettenheim P, and Gill F, eds). Philadelphia: the academy of natural sciences; The American Ornithol ogists Union, Washington, DC. Drent RH, 1970. Functional aspects of incubation in herring gull. Behaviour 17(suppl.):1-132.

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27 Dykstra CR, and Karasov WH, 1992. Changes in gut structure and function of house wrens (Troglodytes aedon ) in response to increased ener gy demands. Physiological Zoology 65:422-442. Eikenaar C, Berg ML, and Komdeur J, 2003. Expe rimental evidence for the influence of food availability on incubation attendance and hatching asynchrony in the Australian reed warbler Acrocephalus australis Journal of avian biology 34:419-427. Franks 1967, The responses of incubating Ringe d Turtle Dove (Strep topelza rzsorza) to manipulate egg temperatures. Condor 69:268-276. Grant GS, 1982. Avian incubation: egg temper ature, nest humidity, and behavioral thermoregulation in a hot environment. Ornithological monograph No. 30. American Ornithologists Union, Washington, DC. Hans-Christian S, Eshiamwata GW, Munyekeny e FB, Griebeler EM, and Bhning-Gaese K, 2005. Nest predation is little affected by parent al behaviour and nest site in two African Sylvia warblers. Journal of Ornithology 146:167-175. Hilton A, and Armstrong R, 2006. Post hoc ANOVA tests. Microbiologist 7:34-36. Jackson JA, 1985. On the control of parasites in nest boxes and the us e of pesticides near birds. Sialia 7:17-25. Lloyd JD, and Martin TE, 2004. Nest-site preferen ce and maternal effects on offspring growth. Behavioral Ecology 15:816-823. Martin TE, 1987. Food as a limit on breeding birds: A life-history perspectiv e. Annual Review of Ecology and Systematic 18:453-487. Martin TE, Scott J, and Menge C, 2000. Nest predation increase with parental activity: separating nest site and parent al activity effects. Proceed ings Royal Society of London. Series B 267:2287-2293. Martin TE, 2004. Avian life-history evolution has an eminent past: does it have a bright future? Auk 121:289-301. McWilliams SR, Caviedes-Vidal E, and Kara sov WH, 1999. Digestive adjustments in Cedar Waxwings to high feeding rate. Jour nal of experimental zoology 283:394-407. McNab BK, 2002. The physiological ecology of verteb rates. Cornell University press, Ithaca, New York. McNab BK, 2005. Food habits and the evolution of energetics in birds of paradise (Paradisaeidae). Journal of comparative physiology B 175:117-132. Muchai M, and Plessis, MA, 2005. Nest predation of grassland bird species increases with parental activity at the nest Journal of avian biology 36:110-116.

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28 Nagy LR, and Holmes RT, 2005. Food limits annual fecundity of a migratory songbird: an experimental study. Ecology 86:675-681. Nilsson J 1994. Energetic bottle-necks dur ing breeding and the reprod uctive cost of being too early. Journal of Animal Ecology 63:641-647. Piersma T, and Morrison RIG, 1994. Energy expend iture and water turnover of incubating ruddy turnstones: high costs under high ar tic climatic conditions. Auk 111:366-376. Rastrogi A, Zanette DL, and Clinchy M, 2006. Food availability a ffects diurnal nest predation and adult antipredator beha vior in song sparrows, Melospiza melodia Animal behavior 72:933-940. Reid, JM, Monaghan P, and Ruxton GD, 1999. The e ffects of clutch cool ing rate on starling, Sturnus vulgaris incubation strategy. Animal Behaviour 58:1161-1167. Ricklefs RE, 1987. Comparative analysis of the avian embryonic growth. In: Development of the avian embryo (Metcalfe J, Stock MK, and I ngermann RL, eds). Alan R Liss, Inc., New York; 309-324. Sanz JJ, 1996. Effects of food availability on incubation period in the pied flycatcher ( Ficedula hypoleuca ). Auk 113:249-253. SAS institute, 2003. SAS/STAT Users Guide, version 9.1. SAS Institute, Cary, North Carolina. Shaffer TS, 2004. A unified approach to analyzing nest success. Auk 121:526-540. Skutch AF, 1962. The constancy of incubation. Wilson Bulletin 74:115-152. Thomson DL, Monaghan P, and Furness RW, 1998. The demand of incubation and avian clutch size. Biological Review 73:293-304. Tinbergen JM, and JB, Williams, 2002. Energetics of incubation. In: Avian incubation Behaviour, Environment, and Evolution (Deemi ng, DC, ed). Oxford University Press, New York; 299-313. Turner JS, 2002. Maintenance of egg temp erature. In: Avian incubation Behaviour, Environment, and Evolution (Deeming, DC, ed). Oxford University Press, New York; 119142. Vleck CM, 1981a. Energetic cost of incuba tion in the Zebra finch. Condor 83:229-237. Vleck CM, 1981b. Hummingbird incubationfema le attentiveness and egg temperature. Oecologia 51:199-205. Walther BA, and Clayton DH, 1997. Dust-ruffling: A simple method for quantifying ectoparasite loads of live birds. Journal of Field Ornithology 68:509-518.

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29 Weathers WW, and Sullivan KA, 1989. Nest atten tiveness and egg temperat ure in the yellow-eye junco. Condor 91:628-633. Weeden JS, 1966. Diurnal rhythm of attentiven ess of incubation female tree swallows ( Spizella arborca ) at a northern latitude. Auk 83:368-388. Wiebe KL, and Martin K, 2000. The use of incubati on behavior to adjust avian reproductive cost after egg laying. Behavioral Ecology and Sociobiology 48:463-470. Williams JB, 1993. Energetics of incubation in fr ee-living Orange-breasted sunbirds in South Africa. Condor 95:115-126. Williams JB, 1996. Energetics of avian incubatio n. In: avian energetic s and nutrition ecology (Carey C, ed). New York: Chapman & Hall; 375-416. Zebra E, and Morton ML, 1983. Dynamics of in cubation in Mt. White-crowned sparrows. Condor 85:1-11. Zimmerling R, and Ankney CD 2005. Variation in incubati on patterns of Red-winged Blackbirds nesting at lagoons and pounds in eastern Ontario. Wilson Bulletin 117:280-290.

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30 BIOGRAPHICAL SKETCH Gustavo Adolfo Londoo was born in 1 976 in Cali, Colombia. The older of two children, he grew up mostly in Cali, Colombia, graduating from Gimnasio la Colina High School in 1993. After his high school graduation, he spent 1 year in Morton, Illinois, as an exchange student. In fall 1994 he enrolled the Universida d de los Andes, Bogota, Colombia, where he started his biology bachelors degree. During his undergrad career Gu stavo was involved in many field research programs that principally involved birds. Af ter finishing his B.S. in biology in 2000, Gustavo was involved in bird field projec ts in different countries, Canada, Costa Rica, Per and Colombia. In 2003 he participates in the Organization for Tropi cal Ecology field course in ecology and conservation in Costa Rica. Gust avo work with Wildlif e Conservation Society Colombia program from 2002-2004, ga thering data to develop cons ervation strategies for some endanger Andean birds in Colombia that affect incuba tion behavior of the Northern Mockingbird. Upon completion of his masters program, Gu stavo will begin working toward his Ph.D. At the Zoology Department, University of Flor ida under the advice of Douglas Levey and Scott Robinson where he will study factor s that affect incubation behavi or of high elevation tropical birds.