A Preliminary Comparison of Marine Bird Biomass and Food Consumption Between the Southeastern Bering Sea and Parts of the Southern Ocean

Abstract

Seabird density, biomass and C demand were compared in open waters of the southeastern Bering Sea shelf and the Argentine shelf at comparable latitudes and seasons; comparisons were also made for waters near Bering Sea colonies and near the South Orkney Islands. Away from colonies, seabird densities were generally higher in the Bering Sea than off southeastern Argentina, but the biomass of seabirds was similar. However, since the mean weight of birds in the Bering Sea was less than that off Argentina, C demand was higher in the Bering Sea as a consequence of the allo-metric nature of the metabolic equations. Similarly, limited sampling near the South Orkney Islands encountered a lower density of birds than sampling near islands at comparable latitudes in the Bering Sea. Again, the biomass of birds near the South Orkney Islands was similar to that found near the Bering Sea colonies due to the larger mean size of the southern hemisphere birds, but overall C demand of seabirds was similar or somewhat greater in the Bering Sea. Seabird use of the waters near the South Orkney Islands may have been under-estimated due to the departure of birds for moulting.