Intraspecific variation in environmental and geographic space use: insights from individual movement data Anne-Sophie, Corinne, Laure, Bonnet-Lebrun St John’s College Evolutionary Ecology Group Department of Zoology University of Cambridge This dissertation is submitted for the degree of Doctor of Philosophy March 2018 1 Author’s Declaration This dissertation is the result of my own work and includes nothing which is the outcome of work done in collaboration except as declared in the Preface and specified in the text. It is not substantially the same as any that I have submitted, or, is being concurrently submitted for a degree or diploma or other qualification at the University of Cambridge or any other University or similar institution except as specified in the text. I further state that no substantial part of my dissertation has already been submitted, or, is being concurrently submitted for any such degree, diploma or other qualification at the University of Cambridge or any other University or similar institution. The main text does not exceed the prescribed word limit for the relevant Degree Committee (School of Biology). 2 Summary Species’ ranges arise from the interplay between environmental preferences, biotic and abiotic environmental conditions, and accessibility. Understanding of – and predictive models on – species distributions often build from the assumption that these factors apply homogenously within each species, but there is growing evidence for individual variation. Here, I use movement data to investigate individual-level decisions and compromises regarding the different costs and benefits influencing individuals’ geographic locations, and the species-level spatial patterns that emerge from these. I first developed a new method that uses tracking data to quantify individual specialisation in geographic space (site fidelity) or in environmental space (environmental specialisation). Applying it to two species of albatrosses, I found evidence of site fidelity but weak environmental specialisation. My results have implications for how limited research efforts are best-targeted: if animals are generalists, effort are best spent by understanding in depth individual patterns, i.e., better to track fewer individuals for long periods of time; whereas if animals tend to be specialists, efforts should be dedicated to tracking as many individuals as possible, even if for shorter periods. I then investigated individual migratory strategies and their drivers in nine North American bird species, using ringing/recovery data. I found latitudinal redistribution of individuals within the breeding and non-breeding ranges that generally did not follow textbook patterns (‘chain migration’ or ‘leapfrog migration’). Migratory individuals tend to trade off the benefits of migration (better tracking of climatic niche; better access to resources) and its costs (increasing with migratory distance). I found that birds are more likely to remain as residents in areas with warmer winter temperatures, higher summer resource surpluses and higher human population densities (presumably because of a buffering effect of urban areas). Overall, my results highlight the importance of considering individual variation to understanding the ecological processes underpinning species’ spatial patterns. 3 Acknowledgements Like the birds in this thesis, I spent my PhD migrating between two seasonal ranges: one in Cambridge, in the Zoology Department and one in Montpellier, at the Centre d’Ecologie Fonctionnelle et Evolutive. My general thanks go to all the people I have met in these two amazing places and who have made this thesis possible and enjoyable. I would like to start by thanking my supervisors, Andrea Manica at the University of Cambridge and Ana Rodrigues at the CEFE. Thank you for your scientific and moral support throughout my PhD. Thank you for everything you taught me, for your patience and for staying enthusiastic even when I was convinced that everything was going wrong. I am also grateful to Richard Phillips, with whom I collaborated on the project which, despite being only one chapter of this thesis, took me most of my PhD time. Thank you for your data, your comments on my drafts and your ecological insights. I would also like to thank my PhD advisors Bill Sutherland and Andrew Balmford for insightful comments on my project, and my PhD examiners Aldina Franco and Nick Davies for their time and insights on my different chapters. Another warm thank to those who have given their time to discuss ideas or read some of my drafts: to Tommy, Ana, Nico, Victor and my migratory companion, Marius – your excitement for science is contagious. An even more special thanks to Rémi for all the drafts you read and all the time you spent listening to me trying to make my mind clear. The journey through this PhD would not have been possible without the financial support of St John’s College, whose Benefactors’ scholarship funded my PhD. It also would not have been possible without those who contributed the data I used for this thesis: the British Antarctic Survey (Chapter 3) and all the employees of the Bird Banding Lab and the many volunteers who collected the ringing data I used in Chapters 4 to 6. This PhD was not only the story of a migration, but also one of a fledging event: for this I have to thank all the additional people who helped me learn how to be a scientist. Thank you to Paulo Catry, Ewan Wakefield and Thierry Boulinier for giving me the chance to do fieldwork and for triggering my curiosity and interest for seabirds. Thank you to Jérémy Tornos for everything you taught me in the field. And because, to me, a good scientist is not only a researcher but also a teacher, I would like to thank all the ones who trusted me in giving me the many teaching opportunities I had in these last years: in particular, Will Cresswell, David Aldridge, Bill Amos and David Labonte. 4 The incredibly stimulating environments I was working in also highly helped me fledge as a scientist. Both the Zoology Department and the CEFE are amazing places to work at: places with opportunities to discuss research – be it the Stats Club in the David Attenborough Building, the Student Conference for Conservation Science in Cambridge (a yearly highlight of my time in Cambridge), the journées DPB, the JCM or the student seminars at the CEFE –, places with very smart people to interact with and exciting seminars to attend. Not only stimulating, my working environment has also been incredibly friendly. For this I would like to thank all the amazing people whose path crossed mine in my two labs in these last years: all the people in the (extended) Evolutionary Ecology group: Marius, Tommy, Ana, Dave, Max, Veronika, Riva, Freddie, Robert, Stephen, Mario, Anahit, Maanasa, Ana… ; all my Happy Hour companions at the Zoology Department; all my colleagues at the CEFE: Ana, Anne, Jean-Louis, Paul, Simon, Simon, Marius, Sophie, Sophie, Louise, Guillaume, Marie, Adrien, Noémie, Eva, Sarah, Fabien, Carole, Fred, Alice, Clémence, Laeti, Olivier, Gilles, Stpéhane, Fede, Hugo, Nico, Rémi, Adrien, Amémé, Manon, Alexis, Giorgia, Pascal, Julie, Camille, Victor, Agathe, Elodie, Lorelei, Thomas, Laure, Soumaya, Aïssa, Mathias, Matthias, Charlotte, Charlotte, Antoine… Thank you all for creating such a lovely place – and for all the “goûters”: like the birds in this thesis, I understood the importance of “resource surpluses”! Finally, because an efficient work and a happy life often go together, I would also like to thank all the people who have made my life easier in both countries: the staff at St John’s who have always been helpful; the lovely people I have lived with in the last years: Nina, Valentina, Thomas, Sixtine, Sylvain… ; all my other friends in Cambridge – Laura, Juan Pablo, Mike, Tim, Matt, Chris, Young Mi, David, Yulia, Ben and Vix… – and in Montpellier – Vincent, Nadine, Ariane, Jose… ; but also all the important people that were present (more or less) along my migratory path: my friends in Paris and elsewhere, and, in particular, my family: thank you for supporting me and for understanding my aspiration to follow a somehow different path (to be forever studying, not to be rushing to get “a proper job” and to do what I enjoy). Although they have been incredibly stimulating, it would probably be lying not to say that these PhD years have also been hard. So I would like to dedicate this PhD to the people who supported me in times of self-doubt and helped me bounce back – there have been many, but I am particularly grateful to Laeti, Nico, Veronika, Elodie, Maanasa and Rémi. Thank you all! 5 Table of contents 1. General introduction ........................................................................................................... 11 1.1. Drivers of species distributions ..................................................................................... 11 1.2. An individual-level perspective .................................................................................... 13 1.3. Objectives ....................................................................................................................... 17 1.4. Thesis outline ................................................................................................................. 17 2. Methods for detecting and quantifying individual specialisation in movement and foraging strategies of marine predators .................................................................................. 19 2.1. Abstract..........................................................................................................................