FORAGING BY MURRES (URIA SPP) AT TIDAL FRONTS SURROUNDING THE PRIBILOF ISLANDS, ALASKA, USA

We investigated the foraging distribution of 2 species of murres (Uria lomvia and U. aalge) in relation to Acoustically Determined Biomass ( ADB) and hydrographic structure surrounding the Pribilof Islands, Beri ng Sea, Alaska, USA. The distribution and abundance of both murre spec ies were similar; therefore, we combined data for thick-billed and com mon murres in the analysis. We found that murre densities were higher in frontal regions than in non-frontal regions. Maximum ADB was also f ound to be elevated in the frontal zone. Within frontal regions, high densities of murres were associated with regions containing relatively high levels of ADB. In contrast, we did not find significant correlat ions between murre density and ADB in the study area as a whole. We po stulate that murres restrict their foraging to the frontal region beca use prey can be located more predictably within this zone than in othe r areas in the vicinity of the Pribilof Islands.