Feeding ecology of Kittlitz's and Marbled murrelets in Prince William Sound, Alaska

We studied the feeding ecology of Kittlitz's (Brachyramphus brevirostris) a nd Marbled (B. marmoratus) murrelets in Prince William Sound, Alaska, durin g 1996-1998 in relation to environmental characteristics and other attribut es (e.g., time of day, season). The proportion of feeding Kittlitz's Murrel ets was significantly affected by survey type season, year, habitat type, i ce cover, distance from shore, water depth, and shoreline substrate. The pr oportion of feeding Marbled Murrelets was significantly affected by survey type, time of day, year, habitat type, ice cover, sea-surface temperature a nd salinity distance from freshwater input, distance from shore, water dept h, and shoreline substrate. Both species primarily ate the common forage fi shes that occurred in these glaciated fjords, except in early summer, when it appears that they forage extensively on pelagic invertebrates. Prey spec ies and mean sizes of fishes eaten, occurrence in mixed-species feeding flo cks, and dive times were similar between species. Thus, the two species exh ibit extensive ecological overlap in feeding during summer.