Associations between seabirds and water-masses in the northern Pacific Ocean in summer |
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| Authors: | T. R. Wahl D. G. Ainley A. H. Benedict A. R. DeGange |
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| Affiliation: | (1) Department of Biology, Western Washington University, 98225 Bellingham, Washington, USA;(2) Point Reyes Bird Observatory, 94970 Stinson Beach, California, USA;(3) NOAA/HAZMAT Office, 98115 Seattle, Washington, USA;(4) US Fish and Wildlife Service, 99503 Anchorage, Alaska, USA;(5) Present address: 3041 Eldridge, 98225 Bellingham, Washington, USA |
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| Abstract: | Seabirds were systematically censused during more than 6 000 transect counts from research vessels in the North Pacific Ocean and Bering Sea during the summers of 1975 to 1984. Density indices were calculated for 1o latitude-longitude blocks for 71 species. Blocks were assigned to oceanographic regions (current systems and domains) on the bases of geography, sea surface temperature and salinity. Bird abundances across regions were patchy; concentrations occurred at boundaries. Regional avifaunas overlapped as a function of three factors: similarity of water-types, geographic adjacency, and proximity to nesting areas. Four major avifaunas were apparent: the Bering Sea (and adjacent regions), the Subarctic Current System/Transition Domain (and adjacent regions), Upwelling Domain, and North Pacific Central Water. The subarctic boundary sharply separated different avifaunas. Ocean productivity may be the factor that ultimately affects avifaunal composition. |
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