Decadal-scale seabird assemblages in Prydz Bay, East Antarctica

Abstract

A total of 26 species/taxa make up the seabird community of Prydz Bay, East Antarctica, of which 9 are resident breeding species. Analyses of almost 32 000 at-sea observations over 20 yr (1980/81 to 2001/02) identified 3 assemblages. Observations of Assemblage 1, which included the 9 resident species, were consistent with the influx, presence and departure of breeding birds to their colonies around Prydz Bay. Assemblage 2 was comprised of all seabird species/taxa reported from Prydz Bay and represented an overlap (in time and space) assemblage, being observed in late summer in central Prydz Bay. Assemblage 3 consisted principally of the non-resident species/taxa that visit Prydz Bay every summer from sub-Antarctic and temperate breeding localities. This assemblage was observed most frequently in mid to late summer and well offshore. Two species were found to be indicator species of all 3 assemblages; this is proposed to be a result of their Antarctic and sub-Antarctic breeding distributions that in turn produce broad ranges in their at-sea distributions in the Southern Ocean. Assemblage 1 is similar to the pack-ice associated seabird assemblage identified elsewhere around the Antarctic, differing only in species composition due to species' breeding distributions at regional scales. Analyses at finer temporal scales (decadal and semi-decadal) identified the same assemblages, indicating the stability of seabird assemblages over the 1980/81 to 2001/02 period within Prydz Bay.