Behavioural ecology of the red-capped robin (photo: Tobias Sahlman) Submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy Damian Kimon Dowling May 2004 Department of Zoology University of Melbourne Abstract In this thesis, I describe aspects of the behavioural ecology of the red-capped robin Petroica goodenovii (Petroicidae), relating to its mating system and breeding biology, based on field research during two breeding seasons (2000/01 and 2001/02) in Terrick Terrick National Park (northern Victoria, Australia). Breeding traits of the red-capped robin were typical of many other Australian passerines and included small clutches, long breeding seasons and multiple broods. A comparative analysis within the Petroicidae (members of which are distributed throughout Australasia) revealed that species endemic to Australia had shorter incubation periods, and species from semi-arid and dry woodlands had comparatively longer incubation periods. Red-capped robin abundances within white cypress-pine woodlands of Terrick Terrick National Park were higher than those of nearby eucalypt woodlands, suggesting such pine woodlands provide high quality habitat for red-capped robins. The study site was saturated with robin breeding territories and few territory vacancies were available at any given time. Nestlings that were relatively heavier were more likely to reach independence and disperse. However, rates of juvenile recruitment into the study population were low. Juveniles may be forced to disperse far from their natal territories to establish breeding territories. To investigate the role of sexually dichromatic plumage in the mating system of the red- capped robin, I isolated and characterised seven hypervariable microsatellite loci from the red-capped robin for use in paternity analyses. Five loci showed no evidence of null alleles, and together with two loci gained by cross-amplification, were suitably polymorphic for paternity analysis (exclusion probability for seven unlinked loci = 0.9760). Extra-pair matings comprised 23% of fertilisations in this population. Males with the highest reproductive success in 2000/01 moulted into the most colourful plumage at the i conclusion of this season, suggesting red plumage may be a condition-dependent signal of quality. These males were in better body condition than other males during the study. Males with the most colourful forehead caps paired with the highest quality females, but the most colourful males did not gain increased reproductive success (within- or extra- pair) during the season they possessed their colourful plumage (2001/02). Instead, male reproductive success correlated with body condition, age, and the age of his social partner. When females gained extra-pair fertilisations, extra-pair males were more heterozygous and tended to be more distantly related to the social female than their within-pair counterparts. In females, the length of the rufous forehead patch was related to reproductive success; females with longer caps initiated breeding earlier in the season and produced more offspring than smaller-capped females. Multiple factors were correlated with nestling sex. Extra-pair chicks tended to be sons more often than daughters, and yearling males (which possess female-like plumage) were more likely to sire sons than adult males in bright plumage. Adult females and yearling females in high body condition produced more sons than yearling females in poor condition. Sons were more likely to survive to nutritional independence than daughters when produced by adult females, but less likely when produced by yearling females. Sex allocation in this species may be maintained by differing production costs for each sex, and genetic benefits to females of producing sons when fertilised by males of high genetic quality. ii This is to certify that (i) the thesis comprises only my original work except where indicated in the preface, (ii) due acknowledgement has been made in the text to all other material used, (iii) the thesis is less than 100,000 words in length, exclusive of tables, maps, bibliographies and appendices. Damian K. Dowling May 2004 iii Preface The research reported in this thesis was conducted with approval from the Faculty of Science Animal Experimentation Ethics Sub-committee at the University of Melbourne (reg. No. 99127) under Department of Natural Resources and Environment (now Department of Sustainability and Environment) permit numbers 10001446 and 10001853 and Australian Bird and Bat Banding Scheme authority number 2432. Some fieldwork was conducted with the assistance of volunteers, working under my supervision. In particular, these assistants contributed to the collection of plumage colour measurements (reflectance spectrophotometry) in which accurate data collection required two people (Chapter 5). They also assisted with bird capture and measurement by helping set-up mist-nets and recording data, and assisted with nestling measurement by helping set-up climbing equipment and recording data (Chapters 2, 3, 5, 6). Assistants also scanned areas outside the immediate study site for colour-banded juveniles that had dispersed from their natal territories (Chapter 3) and searched for nests outside of my study site (as part of an experiment not included in this thesis). All field assistants are mentioned in the acknowledgements section. This thesis is a series of five papers (Chapters 2-6), preceded by a chapter of aims (Chapter 1) and conclusions (Chapter 7). This approach has led to some repetition in the methods sections. Chapter 2 is published in Australian Journal of Zoology (2003) 51, 533-549. Chapter 3 is published in Emu (2003) 103, 199-205, co-authored by Mark Antos and Tobias Sahlman. Mark conducted the population abundance transects and produced figure 3 and located the colour-banded robin in Gunbower State Forest. Tobias helped locate juveniles following natal dispersal in areas surrounding the study site. Chapter 4 is published in Molecular Ecology Notes (2003) 3, 517-519, co-authored by Greg Adcock and Raoul Mulder. Greg taught me the molecular techniques required to develop microsatellite markers. I conducted the lab work and analysis myself. In addition to Chapter 4, Raoul will co-author Chapters 5 and 6 when published. On these papers, Raoul provided detailed advice and feedback. I am the principal contributor to all chapters in this thesis, and the primary author on all publications arising from this thesis. iv Acknowledgements I am greatly indebted to Raoul Mulder for his fantastic supervision and input throughout this PhD. Since first meeting Raoul, he has been continually enthusiastic and accessible, always generous with support, assistance, drafting and advice; and a friend. Thanks for giving me this fulfilling opportunity to follow my interests in behavioural ecology. I am very thankful to everyone that volunteered in assisting me at my field-site, who in doing so made the work much more manageable and enjoyable. In particular, thanks to Tobias, who came to Australia and devoted two months to fieldwork on the robins. Deborah, Sophie and Michelle provided invaluable assistance for a few weeks. Jessica, Nina and Thijs all provided invaluable assistance for shorter periods. I am very fortunate to have so many friends that were willing to come to my field-site to help me. I would like to thank Anne for her help. Wouter, Amy, Dave, Grainne, Robert and Tania all made fieldwork much more fun in the early days. Sorry for only providing you with the peanut butter sandwiches, but I thought you would all love them. I also thank Mark Antos. My field site doubled as one of his, and our sporadic, unplanned meetings sparked a collaboration. I will always be indebted to Barry and Lois Schramm for their willingness to have me stay with them and their unending hospitality and kindness to both myself and my field assistants, during my stays in Mitiamo. Thanks to Wouter for taking me through the basics in the molecular lab. I am very grateful to Greg for teaching me techniques required for microsatellite isolation and characterisation, and his assistance. I thank Iain for help in the lab and for helpful discussions. There are many people within the Zoology Department that I am grateful to. Mark Elgar gave me much valuable advice and assistance over these years. I thank Michael Magrath v for reading drafts of my manuscripts, many helpful discussions and statistical advice. Thanks to David Morgan, Ken Kraaijeveld and Ellen van Wilgenburg for reading drafts of chapters and for helpful discussions. Thanks to Mick Keough, Steve Swearer and Therésa Jones for discussions regarding statistical analysis. I thank David Paul for advice with preparing posters for conferences, and for help in preparing figure 1, Chapter 3. Thanks to Marilyn Renfree and David Macmillan, who as Heads of the Department, and to Mick Keough and Mary Familari, who as post-graduate coordinators, saw to all of my immediate requirements. I am very thankful to the department for awarding me the funds that enabled me to complete the project, and for the Drummond Awards that enabled me to attend ISBE 2002 (thanks!) and to visit Staffan Andersson and his lab group in Göteborg, Sweden. I am very grateful to Josie, Sharon, Terry, Peter, Diana and Barb for their fantastic administrative help that made my life a lot easier, to Viv and Jo for help with organising field equipment and Bruce Abaloz for advice regarding avian haematology. I thank everybody in our ‘evolutionary ecology’ lab group for providing a great weekly forum to discuss current research and ideas. I am very grateful to Graham Hepworth from the Statistics Consulting Unit, at the University of Melbourne, for many hours of advice regarding generalised linear modelling and mixed modelling. I sincerely thank the Holsworth Wildlife Research Fund and Birds Australia, who through the Stuart Leslie Bird Research Award and VicGroup Research Grant, generously funded my research. I thank Staffan Andersson and Anette Johansson for analysing the red-capped robin feather samples for carotenoid content, and Staffan for hosting me in Göteborg and for fantastic feedback and advice on the project.