Seabird distribution, abundance and diets in the eastern and central Aleutian Islands

We examined the hypothesis that seabird distribution, abundance and diets differ among the eastern and central Aleutian Islands in response to distinct marine environments and energy pathways in each region. Research cruises were conducted in June 2001 and May-June 2002. We determined the distribution, abundance, diet and prey consumption of seabirds, and related these to zooplankton abundance and water masses that possess different physical properties. We found that distribution, abundance and diets of seabirds could be partitioned into two regions that correspond to marine environments determined by the extent of the Alaska Coastal Current along the eastern and central Aleutian Islands. Short-tailed shearwaters (Puffinus tenuirostris) were the most abundant seabird in the coastal waters of the eastern Aleutian Islands, and northern fulmars (Fulmarus glacialis) were the most abundant seabird in the oceanic waters of the central Aleutian Islands. Seabird communities in the central and eastern Aleutian Islands were likely associated with different food webs. In the central Aleutian Islands, short-tailed shearwaters and northern fulmars consumed shelf-break species of euphausiids (Thyssanoesa longipes) and oceanic copepods (Neocalanus cristatus), respectively; in the eastern Aleutian Islands, both short-tailed shearwaters and northern fulmars consumed shelf species of euphausiids (T. inermis). Carbon transport to seabirds was highest in Unimak and Akutan Passes where shearwaters removed large quantities of shelf euphausiids, followed by Samalga and Seguam Passes where northern fulmars removed large amounts of oceanic copepods.