The distribution and abundance of breeding and foraging seabirds is usually a reflection of the availability of prey in the marine ecosystems on which the birds depend. At the scale of hundreds of km, differences in marine communities may be reflected in variation in the species composition of resident seabirds. At small scales, environmental features such as fronts or ice can influence where birds will aggregate to forage. Features at which prey become concentrated near the surface are of particular importance to bird species dependent upon small planktonic organisms. Concentrations of foraging seabirds frequently indicate the presence of such features, or of areas of unusually high prey biomass. The absence of birds does not mean that concentrations of potential prey are absent. “Assembly rules,” by which one might predict aspects of the marine environment that birds should use in selecting foraging areas are proposed. Copyright © 1991, Wiley Blackwell. All rights reserved

A three year study of Herring Gull (Larus argentatus) reproductive success on four islands in Maine indicated that production of young was controlled by different factors operating on the eggs and chicks. Hatching success was inversely related to the disturbance of colonies by picnickers, which apparently caused the adults to leave their eggs exposed to sufficient solar radiation to addle the eggs. The survival of chicks was lower on islands distant from sources of edible refuse (outer islands) than on islands close to sources of waste (inner islands), regardless of visits by picnickers. The nutrition and growth rates of chicks on inner and outer islands were similar. The attendance of parents on the territories was found to be less on an outer island than on an inner island. It is concluded that differences in parental behavior associated with greater foraging effort were responsible for a higher loss of chicks to predation on the outer islands.

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

In the eastern Bering Sea, the overall distribution of least auklets (Aethia pusilia) reflects the distribution of different water masses and their associated plankton communities. Within these water masses, the foraging distribution of least auklets is influenced by physical processes that result in predictable aggregations of prey, most often because of property or flow gradients with which the plankton interact. Examples include the accumulation of zooplankton at, or above, the pycnocline and near-surface patches of plankton concentrated in downwellings formed at convergences. These small-scale processes influence avian use of the larger-scale features. Breeding colonies of least auklets are located within commuting distance of physical features in the ocean at which appropriate prey are concentrated; where large copepods or physical features to concentrate them are absent, auklets do not breed. Thus, control of the distribution of foraging seabirds and their breeding colonies in the eastern Bering Sea is a multi-scale process.

The eastern Bering Sea and the Barents Sea share a number of common biophysical characteristics. For example, both are seasonally ice-covered, high-latitude, shelf seas, dependent on advection for heat and for replenishment of nutrients on their shelves, and with ecosystems dominated by a single species of gadoid fish. At the same time, they differ in important respects. In the Barents Sea, advection of Atlantic Water is important for zooplankton vital to the Barents Sea productivity. Advection of zooplankton is not as important for the ecosystems of the southeastern Bering Sea, where high levels of diatom production can support production of small, neritic zooplankton. In the Barents Sea, cod are the dominant gadoid, and juvenile and older fish depend on capelin and other forage fish to repackage the energy available in copepods. In contrast, the dominant fish in the eastern Bering Sea is the walleye pollock, juveniles and adults of which consume zooplankton directly. The southeastern Bering Sea supports considerably larger fish stocks than the Barents. In part, this may reflect the greater depth of much of the Barents Sea compared with the shallow shelf of the southeastern Bering. However, walleye pollock is estimated to occupy a trophic level of 3.3 as compared to 4.3 for Barents Sea cod. This difference alone could have a major impact on the abilities of these seas to support a large biomass of gadoids. In both seas, climate-forced variability in advection and sea-ice cover can potentially have major effects on the productivity of these Subarctic seas. In the Bering Sea, the size and location of pools of cold bottom waters on the shelf may influence the likelihood of predation of juvenile pollock. © 2005 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.