Broadscale density and aggregation of pelagic birds from circumnavigational survey of the Antarctic Ocean

• Main Authors: Veit, Richard R., Hunt, George L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Ornithologists Union 1991
• Subjects: Antarctic; Antarctic Ocean; The Antarctic; Antarc*; Antarctica; Iceberg*
• Online Access: https://oceanrep.geomar.de/id/eprint/52331/; https://oceanrep.geomar.de/id/eprint/52331/1/3251.pdf

We analyzed the spatial distribution and habitat relationships of pelagic birds on a circumnavigational cruise of Antarctica. Our analysis focused on two issues. First, we present a quantitative description of the structure of Antarctic seabird assemblages. This descriptive information benefits from a much more longitudinally extensive data set than previously available. Second, we used 18 crossings of the edge of the pack ice and 15 crossings of the continental slope to clarify the spatial relationship between aggregations of pelagic birds and these physical features. Our analysis corroborates the uniformity of bird species composition over the longitudinal range we covered. We found that the habitats with light (2/10 to 6/10 coverage) pack-ice cover had the lowest density and biomass of birds of the four ice habitats (open water, icebergs only, light pack ice, heavy pack ice) surveyed. Even though overall bird abundance was not concentrated at the ice edge, aggregations of individual species were statistically likely to appear there. We found only a slight (34%) elevation in bird biomass over the continental slope, despite repeated previous findings of bird aggregations associated with the Antarctic slope front. Finally, 45% of the seabirds we observed were in three large aggregations. We suggest this concentration demonstrates the importance of localized patches of prey to foraging seabirds in the Antarctic.