MEPS prepress abstract  -  DOI:

Persistent annual migration patterns of a specialist seabird

Rachael A. Orben*, Nobuo Kokubun, Abram B. Fleishman, Alexis Will, Takashi Yamamoto, Scott A. Shaffer, Rosana Paredes, Akinori Takahashi, Alexander S. Kitaysky


ABSTRACT: Specialization can make animals vulnerable to rapid environmental changes. For long-lived seabirds, foraging specialization may make individuals especially sensitive, as climatic changes are currently occurring over the course of one lifetime. The Bering Sea is a dynamic subarctic and arctic ecosystem where windblown sea ice mediates annual productivity and subsequent pathways to upper trophic levels. Red-legged kittiwakes are an endemic surface foraging seabird specializing on myctophid fishes during reproduction. Their degree of specialization outside the breeding season is less understood. Here we examine their non-breeding ecology (migrations, distributions, isotopic niche) during four years with varying sea ice extent. Although we found annual variation in core distributions, diets (as reflected in feather stable isotope signatures) and outbound migratory timing, the winter range of red-legged kittiwakes was restricted to the western regions of the Bering Sea and North Pacific. Contrary to expectations, sea ice did not limit distributions in the Bering Sea in three years: e.g. sea ice associations (<100 km) were infrequent (8.7% per month). Yet, their wintering range often overlapped with areas of seasonal ice cover, suggesting range-wide use of sea ice ecosystems. Stress levels measured by corticosterone in feathers were generally low. However, birds that concentrated in the Bering Sea in February had higher stress levels and fed at a lower trophic level than those in the western Aleutians and western subarctic. As conditions change, this persistence in wintering locations, while incurring differential stress levels, may contribute to rapid population fluctuations as has been observed in the recent past.