ECOLOGICAL SEGREGATION OF MURRES (URIA LOMVIA, URIA AALGE) DURING THE NONBREEDING SEASON IN THE NORTHWEST ATLANTIC OCEAN by © Laura McFarlane Tranquilla A thesis submitted to the School of Graduate Studies in partial fulfillment of the requirements for the degree of Doctor of Philosophy Cognitive and Behavioural Ecology Programme Memorial University of Newfoundland May 2014 St. John’s Newfoundland ABSTRACT When resources are limited and similar species co-occur, ecological segregation is likely to occur year-round, through spatial, temporal, behavioural and/or dietary segregation. This study investigates year-round ecological segregation between partially sympatric, congeneric Thick-billed Murres (Uria lomvia) and Common Murres (Uria aalge). In the Northwest Atlantic, the species exhibit a latitudinal divergence in breeding distributions. However, both winter in Low Arctic regions, where the potential for spatial overlap is greater than during the breeding period. Given the inaccessibility of murres at sea, the inter- and intra-specific interactions of murres wintering in the Northwest Atlantic have not been previously studied. Using tracking devices and isotopic analyses, this study integrates spatial and temporal movements during the nonbreeding period, relative overlap of winter habitat, and trophic positions during the nonbreeding period. Thick-billed and Common Murres remained partially segregated throughout the year, with some overlap among particular colony groups. Thick-billed Murres moved over a broad range of latitudes throughout the year, had varied core wintering locations, encountered variable environmental conditions, made variable seasonal movements, and had broad trophic positioning. In comparison, Common Murres concentrated and converged on more narrow wintering areas, where colonies had high spatial overlap, encountered similar environmental conditions with consistent temporal patterns, and occupied similar trophic positions. Habitat segregation occurred mostly spatially; but where spatial overlap was greater, inter-specific dietary segregation increased. Most individual murres (both species) exhibited consistent wintering strategies across 2-3 years, with a few individuals shifting habitats between years. Variation in winter movement patterns stemmed more from between-individual variation (particularly among Thick-billed Murres) than from annual changes within individuals. Ecological segregation is expressed through more varied movement, habitat use, and diets of Thick-billed Murres, resulting in a wider ecological niche that is related both to the range of available habitat and prey, and to inter-specific competitive interactions with Common Murres. Relative connectivity among species and colonies at wintering sites also has implications for overall population vulnerability to spatially-discrete risks or wintering conditions, which will be greater for the relatively concentrated Common Murres than for more dispersed Thick-billed Murres. ii ACKNOWLEDGEMENTS Funding – This research was funded through support from Natural Sciences and Engineering Research Council (NSERC) Discovery Grant (Dr. W.A. Montevecchi); the Wildlife Habitat Canada and Bird Studies Canada Murre Fund of Newfoundland and Labrador (WAM); the Government of Canada’s International Polar Year (WAM and Dr. A.J. Gaston) and Northern Scientific Training (L. McFarlane Tranquilla) Programs, the Polar Continental Shelf Project of Natural Resources Canada (AJG), an NSERC PGS-D Scholarship (LMT), and by logistical and financial support from Environment Canada. Personal financial support for LMT was also generously granted through the Kathleen and Leonard O’Brien Foundation, the British Columbia Housing Corporation, and the Leslie M. Tuck Avian Ecology Scholarship. Permits and Logistics - Research was carried out under a Government of Nunavut Wildlife Research Permit, Canadian Wildlife Service Migratory Bird banding permits NUN-SCI-08-55 and WAM-10322, and Animal Care Committee Permits 0800AG01 (Environment Canada) and WM-01-11 (Memorial University). Thanks also to Anthony Gaston, Grant Gilchrist, Mark Mallory, and Greg Robertson (Environment Canada) for research project development, and coordinating Arctic field logistics. Rick Armstrong of Nunavut Research Institute, and Christine Eberl and Sabina Wilhelm of Environment Canada, provided communications and logistics support. Newfoundland and Labrador Parks Division granted access to the Provincial Seabird Ecological Reserves at the Gannet Islands, Funk Island, and Witless Bay Islands. People - I owe a huge debt of gratitude for the enthusiasm and hard work of many fieldwork heroes: Chantelle Burke, Dave Fifield, Roz Ford, Alyssa Granter, Amy-Lee Kouwenberg, Noelle Laite, Alain Lusignan, my Uncle Philip Merchant, and Pierre Ryan at the Gannet Islands; Kyle Elliott, Tony Gaston, Mark Mallory, Jennifer Provencher, Paul iii Smith, Steve Smith, Ilya Storm, and Kerry Woo at high Arctic colonies; Chantelle Burke, April Hedd, Paul Regular, and Bill Montevecchi at Funk and Gull Islands. In the lab, Dianna Brooks and Andrew Murphy were very helpful doing tissue sample preparation, thus preserving my sanity. Many thanks to you all. For invaluable technical expertise, geolocator processing advice and programming knowledge, I am especially thankful to Dave Fifield who got me started with BASTrak, Multitrace, ArcGIS, Matlab, and R, and helped whenever I got stuck (often), and to Paul Regular, ever-genial R whiz for complicated statistical analyses and graphics. Also very generous with technical advice and time have been Greg Robertson, Richard Phillips, Emily Connelly, and Paul Smith; and April Hedd has been a wonderful mentor-friend with technical advice on science and kids alike! In addition to the listed co-authors, manuscripts in this thesis have been improved by helpful suggestions from Rodolphe Devillers, Tony Diamond, Ian Fleming, Anders Mosbech, and Carolyn Walsh. For help caring for the Two Small Rascals, I owe a great debt to Emily and Martin Connelly, Sarah Jackman, and especially the amazing staff at the MUN Childcare Centre – Roxanne, Lori, Melody, Luke, Jennifer, Candace, Colette, Deanna - without whose help I would not have survived! Many thanks go to Murray, Dorothy, Ruth, Tony, Gloria, and Jim (my excellent Moms and Dads), for continual support for this long PhD adventure, for calling, visiting, and taking care of the kids. Many parents would just wonder why their (ever-aging) child just doesn’t get a job already!! Your understanding has been a wonderful gift. From the beginning, I have been grateful to find a continuously supportive and critically instructive thesis committee, composed of Rodolphe Devillers, April Hedd, and Greg Robertson. And of course, utmost appreciation goes to my inimitable supervisor, Bill Montevecchi, whose enthusiasm for this project and for my skills has buoyed me through the rough bits and convinced me it has all been worth it! Bill, you have been a great mentor, motivator, focuser, and editor for this PhD work, and I will strive to model your positive and supportive outlook. iv To Elliot and Clara, I owe thanks for perspective – for most of your lives so far, I have been a PhD student, yet being your Mom adds another, very welcome dimension to my life. Even though you may not realize it at such a young age, you are what motivates me to continue on with difficult tasks. Having kids at home at the end of every day has been a bittersweet blessing: a reminder that time is passing, a reminder of what is truly important, a reminder to live in the present. Finally, thank you to my wonderful Jim, for moving to Newfoundland with me lock, stock, and barrel; for continually re-convincing me that doing a PhD was a good idea; for your selfless commitment to my work while also sustaining your own challenges; for delicious meals and for bringing music to my life; for Everything. I am so lucky and so thankful to have your constant support and love. This one is for you. v TABLE OF CONTENTS Abstract ............................................................................................................................ i Acknowledgements ........................................................................................................ iii Table of Contents ............................................................................................................ vi List of Tables ................................................................................................................... xi List of Figures ................................................................................................................. xv List of Appendices ........................................................................................................ xxii Chapter 1 - INTRODUCTION AND OVERVIEW ........................................................... 1.1 1.1 Ecological Segregation ...................................................................................... 1.2 1.2 Segregation in the Marine Environment ........................................................... 1.3 1.3 Seabird Spatial Ecology ..................................................................................... 1.5 1.4 Life at Sea during the Nonbreeding Period ....................................................... 1.6 1.5 Study Speces: The Murres (Uria) ...................................................................... 1.8 1.5.1 Murre Winter Ecology .............................................................................