Ecological and Geographical Differentiation of the Winter Fauna of Birds and Mammals in the Seas of Northeastern Russia

The ecological and geographical regularities of the spatial differentiation of the fauna of birds and mammals in the seas of northeastern Russia were studied at the end of the winter period of 1987–1988. The aerial surveys covered the Bering, Chukchi, and East Siberian Seas and the eastern part of the Laptev Sea. Mammals are ecologically associated with open sea areas, sea ice, continental and island coasts, and mainland tundra. Wintering flocks of birds are formed by species of inland mountain streams; species that are common circumpolarly in the Holarctic tundra; and marine species of the continental and island coasts of the North Pacific and the Arctic Ocean, including high-latitude endemics. Seven species of mammals and 23 species of birds have been recorded. There are 22 bird species recorded exclusively in the Bering Sea (24% of the marine avifauna of the Russian Far East). In terms of the number of species represented ( n = 9), the prevalence is held by auks, which are very characteristic of the avifauna of the subpolar marine areas of the Palaearctic. Mammals have been regularly recorded in both the Arctic Ocean and the Pacific research sector. The winter fauna of mammals in the seas of northeastern Russia, which is dominated in terms of the number of species by pinnipeds and cetaceans, makes up 23% of the total mammalian fauna of this region. In the Bering Sea, three areas of concentration of wintering birds have been identified: in the southeast of Chukotka, southeast of Cape Navarin, and south of the Island of St. Lawrence. The maximum density of the bird population (21.8 ind./km 2 ) is in young ice and ice of primary formation—where there are many forage polynyas. The bird population of all types of ice is numerically dominated by fulmar and thin-billed and thick-billed guillemots. Most of the marine mammals are observed on the openings in the contact zones of different types of ice or in the ice openings of autumn formation. Clusters are formed by polar bears near the Wrangel Island, by beluga whales to the east and northeast of Cape Navarin, and by walruses to the south of it. The stability of winter spatial groups of walrus and polar bears in the Arctic Ocean, which annually demonstrated similar levels of abundance, has been established. Winter aerial surveys show that beluga whales and humpback whales are not found north of the Bering Strait, and polar bears are almost never found outside the Arctic Basin.