Ecological structure of a pelagic seabird community in the Southern Ocean

Summary The pelagic avifauna (excluding penguins) of the African sector (30°S–70°S, 20°W–40°E) of the Southern Ocean is described quantitatively, based on 3,005 10-min observation of seabirds during seven oceanic cruises in April 1979 – April 1980. The avifauna is characterized according to species richness, diversity, abundance and biomass. These indices are correlated with groups of birds ordered into principal diet and feeding-method classes. Birds eating either plankton, cephalopods or a mixed diet accounted for 51, 23 and 22% of the total avifaunal abundance and 22, 49 and 25% of the total biomass, respectively. Piscivores were represented poorly. Planktivores were especially abundant south of the Antarctic Convergence and, to a lesser extent, at the sub-Tropical Convergence. Cephalopod-eaters were most abundant north of the sub-Tropical Convergence. The greatest abundance of omnivores occurred where planktivores and cephalopod-eaters were least abundant. The distribution of the planktivores and cephalopodeaters is related tentatively to the availability of the birds' principal prey.