AN ABSTRACT OF THE DISSERTATION OF Suzanne H. Austin-Bythell for the degree of Doctor of Philosophy in Wildlife Science presented on March 5, 2013. Title: Life History and Environmental Influences on Avian Incubation and Parental Care in Songbirds Abstract approved: __________________________________________________________________ William Douglas Robinson Patterns of nest attendance behavior by breeding birds represent a parent-offspring trade-off in which adults balance self-maintenance with parental care decisions. Incubation, in particular, is of interest because adults must provide an environment suitable for embryonic development through nest-building and contact-incubation. We evaluated how adult incubation constancy and nest visitation rates varied with life and natural history traits of temperate and tropical bird species. We found that constancy did not differ by latitude or with nest survival rate. A strong negative correlation between incubation constancy and egg mass relative to adult body mass was present. Birds with low constancy tended to have larger relative egg masses and higher basal metabolic rate. Because adult incubation constancy is relatively plastic (i.e., varies with ambient temperature), birds with larger relative eggs may respond to lower cooling rates rather than direct selection for higher or lower constancy. We then assessed if rates of nest visitation (trips to nests by adults during incubation and nestling phases) followed the predictions of the Skutch hypothesis. Skutch suggested that birds nesting in environments with high levels of nest predation would reduce numbers of trips to their nests so as to minimize the risk of visual detection by nest predators. We found support for the basic pattern predicted by Skutch. We also extended his hypothesis to predict other behavior associated with nesting, such as responses of parents to intruders at the nest. Despite apparently early departure from the nest site, adults with higher visitation rates remained conspicuous around the nest site. Thus, while the flight initiation distance from the human observer was earlier than expected, conspicuousness of behavior was associated with nest visitation rate. Finally, we assessed how an environmental variable, photoperiod, might influence rate of embryonic development in a wild songbird, Sylvia atricapilla. We exposed eggs throughout the incubation period to daily photoperiods consisting of 4 hours of light and 20 hours of dark (4L), 12 hours light and 12 hours dark (12L), 20 hours light and 4 hours dark (20L) and a skeleton photoperiod with two 1-hour pulses of light that framed a 20-hour day. We found that the skeleton treatment group differed significantly from our 4L and 12L, but not the 20L treatment groups. The skeleton photoperiod accelerated embryonic development. We suggest that photoperiod may influence incubation period in wild birds and could account for some portion of the widely observed latitudinal variation in incubation period of songbirds. We encourage others to assess how photoperiod interacts with parental attendance patterns to affect embryonic development. ©Copyright by Suzanne H. Austin-Bythell March 5, 2013 All Rights Reserved Life History and Environmental Influences on Avian Incubation and Parental Care in Songbirds by Suzanne H. Austin-Bythell A DISSERTATION submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Presented March 5, 2013 Commencement June 2013 Doctor of Philosophy dissertation of Suzanne H. Austin-Bythell presented on March 5, 2013 APPROVED: __________________________________________________________________ Major Professor, representing Wildlife Science __________________________________________________________________ Head of the Department of Fisheries and Wildlife __________________________________________________________________ Dean of the Graduate School I understand that my dissertation will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my dissertation to any reader upon request. __________________________________________________________________ Suzanne H. Austin-Bythell, Author ACKNOWLEDGEMENTS I am very grateful to Dr. W. Douglas Robinson for his continued guidance and support. I cannot sufficiently express my appreciation for all of the wonderful advice and encouragement that he's provided along the way. Dr. Michaela Hau, too, has been amazingly helpful in this process. She has served as wonderful role model to me and many other female graduate students. Thanks to my committee, Dr. Tiffany Garcia, Dr. James Hermes, Dr. John Bailey and Dr. Thomas Savage for their input and assistance in moulding my dissertation. Dr. Bob Ricklefs has continued to provide guidance in my work on avian life histories for which I am grateful. Love and thanks to Dr. Tara Robinson for her continued support and making me feel like a member of her family (and for letting me be aunt to the boys, Natchez and Rowdy). I appreciate the logistical support that we received from the staff at Kellogg Biological Station (Michigan State University), Smithsonian Tropical Research Institute (Panama), and Max Planck Institute for Ornithology (MPI; Germany). This work could not have been completed without the help of our field crews including: Ruby Zambrano, Neil Chartier, David Bradley, Lisa Miller, Rebecca Gamboa, Noah Stryker, Jessica Adkins, Jennifer Bruce, and Betzi Perez. Your dedication during long field days has made this work possible. I'm also grateful to the very helpful field technicians and support staff at Radolfzell, in particular Elke Henkenhaf, Antje Weber, Karl-Heinz Siebenrock, Tanja Vogler, and Heidi Schmidt for assistance during my time at MPI. Many thanks to the Robinson and Hau labs for lively discussions and good times, particularly Jenny Ouyang, Maria Echeverry-Galvis, and Tim Grieves. I'm grateful to the wonderful community at MPI for making me feel so welcome during my two field seasons in Radolfzell. Jenny Ouyang and Maria Echeverry- Galvis made my field season evenings more entertaining. Jenny was my field buddy for two years, albeit on a different project, but I can safely say that ticks, fleas and nettles were more interesting having faced them with you (and I don't think I've had a weirder first meeting– there's nothing like spending an hour picking a decapitated tick out of someone's abdomen to get to know a person). Thanks to Caleb Spiegel, my awesome roommate, for the good times in South town. I'm grateful to Barbara for helping me through the rough times. Finally, my family has provided immeasurable support during this time. My mom, Marjean Austin, has always been there when I needed her. My wonderful husband has been my rock throughout this process. He has supported me through all of the tribulations that come with graduate work in addition to the challenges of living apart during field seasons and for the last three years of my degree. He is my partner and my reluctant birding buddy. I would not have made it this far without him. CONTRIBUTION OF AUTHORS Dr. W. Douglas Robinson contributed to all aspects of this dissertation. Dr. Michaela Hau assisted with the study design and writing of chapter 3. Dr. R.E. Ricklefs provided funding for the data presented in chapters 2 and 3, assisted in the study design, and provided comments on drafts of chapter 2. TABLE OF CONTENTS Page CHAPTER 1 – General Introduction: Life history and environmental influences on adult attendance and incubation periods in songbirds.........…………..........1 LITERATURE CITED…………………………….………………............4 CHAPTER 2 – Nest attendance strategies of avian parents during incubation.…...6 ABSTRACT……………………………………………………………......7 INTRODUCTION……………………………………………………….....7 METHODS……………………………………………………………….11 Study areas...………………………………………………...........11 Data collection..…………………………...……………………...11 Constancy............................................................................12 Egg mass, clutch mass, and clutch size...............................12 Incubation period................................................................13 Adult mass and BMR..........................................................13 Cumulative nest survival rate..............................................13 Categorical variables...........................................................13 Summary statistics of continuous variables........................13 ANALYSES………………………………………………………............14 Incubation age category..................................................................14 Multivariate statistics..…………………………………......……..14 Multiple linear regression and model averaging……….................15 RESULTS………………………………………………………………...16 Incubation stages.......……………………………..……………....16 Nonmetric multidimensional scaling…………………………......16 Model selection and model averaging.............................................17 DISCUSSION………………………………………….................………18 ACKNOWLEDGMENTS…………………………….…………..............22 LITERATURE CITED………………………………………...................23 TABLES…………………………………………….……………….........28 FIGURES………………………………………………………………....30 CHAPTER 3 –Life history correlates of adult visitation rate in temperate and tropical birds………………………………............................................................34 ABSTRACT……………………………………….……………………...35 INTRODUCTION……………………………….………………………..35 METHODS……………………………………………………………….38 Visitation rate....…………………………...……………………...38 TABLE OF CONTENTS