Seabird diet at a front near the Pribilof Islands, Alaska
Schneider, D.C., Harrison, N.M. & Hunt, G.L.Jr (1990) Stud Avian Biol 14:61-60
Large concentrations of murres (Uria aalge and U. lomvia) have been reported on the water at sites where bathymetry generates flow gradients near breeding colonies in North America. One such site was located in August 1982, by following streams of murres flying away from the colony on St. George Island, Alaska. We found a well-defined tidal front where murres were diving and feeding on euphausiids on the mixed (landward) side of the front, an area of subsurface convergence. Surtaceforaging birds (Black-legged Kittiwakes Rissa tridactyla and Red Phalaropes Phalaropus fulicaria) were feeding on euphausiids at the surface convergence seaward of the murre aggregation. The feeding success of surface foragers was attributed to surface convergence acting on weakly swimming (injured) euphausiids; that of murres to subsurface convergence acting on negatively phototactic euphausiids. Successful foraging at spatially predictable locations around colonies has important implications for population monitoring, impact assessment, and theoretical treatments of the foraging distribution of colonial seabirds.
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