We will compare seabird foraging location and trip duration for Black-legged Kittiwakes and Thick-billed Murres nesting on two geographically associated islands in the Pribilof group, St. Paul and St. George.
The maximum edge of the winter ice on the Bering Sea shelf is generally nearer to St. Paul than to St. George. St. George is nearer the productive edge of the Bering Sea shelf. To the extent that the influence of ice is greater in the vicinity of St. Paul, seabirds nesting on that island might be differentially affected by the loss of that influence if future warming reduces the incidence of ice in the area.
This study will allow us to confirm where birds from each island forage, and to look at foraging location and trip duration variability among years of differing sea ice extent. This study will work closely with the seabird colony study to determine the effects of foraging behavior on diets, reproductive success and adult survival.
We will examine the relation of seabird distribution to oceanographic and biological features of the eastern Bering Sea. Size, location, and composition of seabird foraging flocks at sea and diet composition can change when prey distribution or abundance changes.
This broad-scale component is closely coordinated with the colony-based seabird projects. At-sea observations will provide data on seabird abundance, distribution, and diet. We will determine seabird responses to changes in oceanographic properties of water masses and to prey type and distribution, and will contrast the patterns of central place foragers (breeding kittiwakes and murres) to that of non-breeding birds (such as shearwaters and albatrosses).
Data collected for this project will also be used to examine seabird and cetacean foraging response to prey persistence, and to retrospectively analyze trophic interactions among fish, birds, and mammals.
These studies focus on response variables for surface-feeding Black-legged Kittiwake and deep diving Thick-billed Murre at breeding colonies on St. Paul and St. George Islands in the Pribilof Islands. We will collect data on seabird reproductive parameters, (clutch size, hatching success, fledgling success, reproductive success, growth rates), timing of nesting events, diets, stress level (part of patch dynamics study B67), annual adult survival, condition of adults (based on body size) and population trends at each island.
We will measure these variables to evaluate inter-annual responses to environmental conditions and prey patch dynamics at breeding colonies on each island. Population indices will be obtained in 2008 and 2011 to provide current data points to assess trends.