UC Irvine

In the Antarctic, seabird species distributions are annular or latitudinal, with strong similarities in species composition of seabird communities in all ocean basins at a given latitude. In the Arctic, communities are arranged meridionally, and show strong differences between ocean basins and, at a given latitude, between sides of ocean basins. In the Antarctic, much seabird foraging is over deep water, and within-season, small-scale patchiness in prey abundance and availability in ice-free waters is likely to be controlled primarily by the behavior of the prey, rather than by physical features. Thus, prey availability may be unpredictable in time and space. In the Northern Hemisphere, most seabird foraging is concentrated over shallow continental shelves, where currents interact with bathymetry to produce predictable physical features capable of concentrating prey or making prey more easily harvested by seabirds. Ice cover appears to be the most important physical feature in the Antarctic. An entire community of birds is specialized to use prey taken near the ice edge. The open-water portion of the marginal ice zone is also an important foraging habitat. In the Arctic, a food web based on underice algae is used by marine birds, but few data exist on avian use of the open water segment of the marginal ice zone. Only rarely does the small-scale abundance of birds match that of their prey; correlations between predators and prey are generally stronger at larger scales. In the Antarctic, largest aggregations of krill may be disproportionately important to foraging seabirds. -from Author