Wintering North Pacific black-legged kittiwakes balance spatial flexibility and consistency.
BACKGROUND
Marine environments are inherently dynamic, yet marine predators are often long-lived and employ strategies where consistency, individual specialization, routine migrations, and spatial memory are key components to their foraging and life-history strategies. Intrinsic determinates of animal movements are linked to physiological and life-history traits (e.g. sex, colony, experience), while extrinsic influences occur as the result of an animal's interactions with either other animals or the environment (e.g. prey availability, weather, competition). Knowledge of the factors affecting animal movements is critical to understand energetic bottlenecks and population dynamics. Here, we attempt to understand the interaction of some of these factors on the winter distributions of a surface-feeding seabird in the North Pacific. Between 2008 and 2011, we tracked 99 black-legged kittiwakes breeding at St. Paul and St. George in the Pribilof Islands, Alaska using geolocation loggers. We tested for colony and sex differences in winter distributions, and individual spatial fidelity over two consecutive winters of 17 individuals. Then we linked tracking data to associated environmental conditions as proxies of prey availability (e.g. sea surface temperature, mesoscale eddies, chlorophyll a, and wind) to understand their influence on kittiwake space use at an ocean basin scale.


RESULTS
Black-legged kittiwakes from both Pribilof Islands primarily wintered in pelagic sub-arctic waters, however, distributions spanned seven ecoregions of the North Pacific. There was a high degree of similarity in area use of birds from the two closely situated colonies and between sexes. Birds tracked for two consecutive years showed higher fidelity to wintering areas than occurred at random. Annual changes were apparent, as distributions were further north in 2009/10 than 2008/09 or 2010/11. This occurred because 70 % of birds remained in the Bering Sea in the fall of 2009, which corresponded with lower October sea surface temperatures than the other two years.


CONCLUSIONS
Although individuals returned to wintering areas in consecutive years, our results suggest that under current conditions individual black-legged kittiwakes have a high capacity to alter winter distributions.
Department of Ocean Sciences, Long Marine Lab, University of California Santa Cruz, Santa Cruz, CA 95060 USA ; Department of Fisheries and Wildlife, Oregon State University, Hatfield Marine Science Center, 2030 SE Marine Science Dr., Newport, OR 97365 USA.
Rachael A
0000-0002-0802-407X
RA
Orben
Department of Fisheries and Wildlife, 104 Nash Hall, Oregon State University, Corvallis, OR 97331-3803 USA.
Rosana
R
Paredes
US Geological Survey-Oregon Cooperative Fish and Wildlife Research Unit, Oregon State University, 104 Nash Hall, Corvallis, OR 97331-3803 USA.
Daniel D
DD
Roby
U.S. Fish and Wildlife Service, 1011 East Tudor Road, MS 341, Anchorage, AK 99503 USA.
David B
DB
Irons
Department of Biological Sciences, San Jose State University, One Washington Square, San Jose, CA 95192-0100 USA ; Institute of Marine Sciences, Long Marine Lab, University of California Santa Cruz, California, 95060 USA.
Scott A
SA
Shaffer
Bering Sea; Black-legged kittiwake; Colony; Fidelity; Geolocation; Non-breeding; Oceanographic habitats; Rissa tridactyla; Sex