ALBERT

Description:    The non-breeding movements of marine birds were poorly known until recently, but this information is essential to understanding the risk to different geographical populations from events on the wintering grounds. We tracked the migration routes and wintering areas of Thick-billed Murre Uria lomvia from two breeding colonies in eastern Canada: Coats Island in northern Hudson Bay and The Minarets, Baffin Island, during the period August 2007–May 2008 using geolocation loggers. Birds from The Minarets moved south rapidly post-breeding and wintered principally off Newfoundland and southern Labrador, or between Newfoundland and southern Greenland, remaining south of 55°N until at least the spring equinox. Those from Coats Island remained in Hudson Bay until at least mid-November, after which they moved rapidly through Hudson Strait to winter in southern Davis Strait and the northern Labrador Sea, mostly north of 55°N. Many individuals stayed throughout the winter in areas of heavy ice cover. Adults from the two colonies appear to be completely segregated in winter and those from Coats Island probably did not enter the area of the winter hunt in Newfoundland. Unexpectedly, some birds from The Minarets wintered in waters beyond the continental slope and outside the distribution of pack ice, demonstrating that particular individuals can be wholly pelagic throughout the winter. Coats Island birds returned through Hudson Strait as soon as open water areas became available in spring. Their sojourn in Hudson Bay coincided very closely with the occurrence of areas with 〈90% ice cover. In spite of the relatively large error in positions obtained from geolocation loggers, our results demonstrated the value of these devices by uncovering a number of previously unknown aspects of Thick-billed Murre non-breeding ecology in the Northwest Atlantic. Comparison of the non-breeding ecology based on SST experienced in winter show that the winter niche is broader than hitherto assumed, demonstrating that separate populations may experience different selection in the face of climate change. Content Type Journal Article Pages 1-13 DOI 10.1007/s00227-011-1704-9 Authors Anthony J. Gaston, Wildlife Research Division, Environment Canada, Carleton University, Ottawa, ON K1A 0H3, Canada Paul A. Smith, Wildlife Research Division, Environment Canada, Carleton University, Ottawa, ON K1A 0H3, Canada Laura McFarlane Tranquilla, Cognitive and Behavioural Ecology Programme, Departments of Psychology and Biology, Memorial University of Newfoundland, St. John’s, NL A1B 3X9, Canada William A. Montevecchi, Cognitive and Behavioural Ecology Programme, Departments of Psychology and Biology, Memorial University of Newfoundland, St. John’s, NL A1B 3X9, Canada David A. Fifield, Wildlife Research Division, Environment Canada, 6 Bruce Street, Mount Pearl, NL A1N 4T3, Canada H. Grant Gilchrist, Wildlife Research Division, Environment Canada, Carleton University, Ottawa, ON K1A 0H3, Canada April Hedd, Cognitive and Behavioural Ecology Programme, Departments of Psychology and Biology, Memorial University of Newfoundland, St. John’s, NL A1B 3X9, Canada Mark L. Mallory, Canadian Wildlife Service, P.O. Box 1714, Iqaluit, NU X0A 0H0, Canada Gregory J. Robertson, Wildlife Research Division, Environment Canada, 6 Bruce Street, Mount Pearl, NL A1N 4T3, Canada Richard A. Phillips, British Antarctic Survey, Natural Environment Research Council, Madingley Road, High Cross, Cambridge, Cambridgeshire CB3 0ET, UK Journal Marine Biology Online ISSN 1432-1793 Print ISSN 0025-3162