Does prey preference affect habitat choice in Antarctic seabirds?

Abstract

Diet composition of the members of two seabird species assemblages in the Scotia-Weddell confluence region, Antarctica, was investigated. One assemblage frequented pack ice and the other was present in adjacent open waters; most members of the latter species assemblage vacated the Antarctic during winter. Cluster analysis showed broad overlap in seabird diet regardless of species, habitat (ice/water mass) or year. Seabirds exploited prey largely according to ranked availability, although they appeared to choose larger fish and crustaceans over smaller crustaceans. Mycotophids in particular, but also krill and squid, were the main prey groups. Diets did not separate on the basis of predator/prey size to any appreciable degree even though a 1000-fold difference in predator size existed. Feeding success (fullness of stomach) of the members of the two species assemblages was highest when in their respective usual habitats. Open-water seabirds appear to lack the specialized foraging behaviors required to exploit the pack-ice environment. Open waters during the winter offer much poorer feeding conditions than those of the pack ice. -from Authors