||Corvallis Environmental Research Lab., OR. ;Point Reyes Bird Observatory, Stinson Beach, CA. ;Old Dominion Univ., Norfolk, VA.;National Science Foundation, Arlington, VA.
The report quantitatively assesses seasonal changes in community structure and habitat selection among seabirds in the Scotia-Weddell Confluence region, Antarctica. Discussed are biological and physical factors underlying the patterns. Data were derived from strip-transects on closely-coordinated multidisciplinary cruises that characterized the physics and biology during Spring 1983, autumn 1986 and winter 1988. Described for the first time ever for the Southern Ocean, seasonal changes in seabird communities in terms of composition, using cluster analysis, as well as relative density and diversity among species. Sea-surface temperature, distance to the pack ice edge and ice type, all physical characteristics of habitat, were the most important environmental variables that affected assemblage composition. Three recurrent assemblages of species were identified. One persistent assemblage, present year round, was associated with the pack ice; another was associated with open waters immediately adjacent to the ice; and a third was a far-from-ice assemblage.