Ecological and geographical structure of bird population on the Onekotan Island (the Northern Kuril Islands)

The ecological and geographical structure of bird population on the Onekotan Island was analyzed using the technique of route count along the transects of unlimited width. The avifauna of the Onekotan Island forms under the system of general zonal-landscape and altitudinal-belt patterns and unites ecological groups of marine and terrestrial species, including mountain ones ( n = 7). The zoogeographic originality of the avifauna is due to a combination of elements of the Pacific, Siberian, Far Eastern island, and Arctic faunistic complexes, as well as Siberian-American and widespread species. The species richness, bird population density, and abundance of most species decrease with altitude. There are 26 species in the avifauna of the forest belt, 17 in the subalpine belt, 14 in the alpine belt, and 29 species in the marine and coastal areas, with population densities of 559, 306, 221, and 129-223 ind./km², respectively. Dominants or subdominants in the population of terrestrial habitats include the Buff-bellied Pipit, Brown-headed Thrush, Siberian Rubythroat, Middendorff’s Warbler, Arctic Warbler, and Pine Grosbeak. Seven species numerically dominate in the population of the marine area, namely Harlequin Duck, Red-faced Cormorant, Slaty-backed Gull, and Pigeon Guillemot (in the coastal part), and Northern Fulmar, Common Guillemot, and Tufted Puffin (at a considerable distance from the coast).