Analyses of the avifauna and bird populations of the island of Onekotan, Great Kuril Islands

Ecological patterns of the formation of bird populations on the Onekotan Island are analyzed. Route counts were used along transects of unlimited width. As many as 53 bird species were registered, including 28% revealed as ubiquitous, another 30% local, and further 32% highly local. 38 species were shown to nest. The taxonomic structure of the avifauna, represented by species from 10 orders, corresponded to the zonal and landscape features of the island’s territories located at the eastern margins of northern Eurasia. Passeriformes (38%), Charadriiformes (24%), Procellariiformes (9%) prevailed. The zoogeographic peculiarity of the avifauna was a composition of elements of the Pacific, Siberian, Far Eastern islands and Arctic faunistic complexes, combined with Siberian-American and widespread species. The avifauna of Onekotan Island, formed by a system of general zonal-landscape and altitudinal-belt patterns, unites ecological groups of marine and land species, including montane ones (n = 7). With altitude, the species richness, the bird population density, and the abundance of most species decrease. There are 26 species in the avifauna of the forest belt, 17 species in the subalpine belt, 14 species in the alpine belt, 29 species in the oceanic waters and coast, with population densities of 559, 306, 221, and 129–223 individuals/km², respectively. The similarity coefficient of the avifauna of oceanic areas is 47%, vs about 60%. of terrestrial habitats. In the population of terrestrial habitats, the dominants and subdominants include the Buff-bellied Pipit, the Brown-headed Thrush, the Siberian Rubythroat, Middendorff’s Grasshopper Warbler, the Arctic Warbler, and the Pine Grosbeak. In the population of the oceanic waters, 7 species dominate in avundance: in its coastal part, the Harlequin Duck, the Red-faced Cormorant, the Slaty-backed Gull, and the Pigeon Guillemot, vs the Northern Fulmar, the Common Guillemot, and the Tufted Puffin at a considerable distance from the coast.