Landscape and Ecological Differentiation of the Fauna and Bird Population of Urup Island (Big Kuril Ridge)

Ecological regularities of the Urup Island landscape differentiation of avifauna and bird population are analyzed. The data were obtained in a 2019 expedition during a survey of the southern part of the Great Kuril ridge. The research was conducted in the vicinity of Novokurilskaya Bay in the northeast of Urup Island and in the vicinity of Shchukin Bay on the Van der Lind Peninsula in the southwest of the island by route accounting on transects of unlimited width at altitudes of 0–200 m above sea level. The commonality of the taxonomic structure and species composition of the avifauna on Urup Island is high; in 2019, 90 bird species were recorded there: 59 on the northeast and 56 on the southwest of the island. The similarity coefficient of local avifauna of the surveyed points (n = 2), which was obtained by the Sørensen formula, is 68%. In all, 38% of species are widespread, 41% are local, and 21% are in isolated foci. Six species were recorded on Urup Island for the first time. The taxonomic structure of the Urup avifauna, formed by species of 12 orders, corresponds to the zonal and landscape features of island territories located near northeastern Eurasia. Passeriformes (39%), Charadriiformes (28%), and Anseriformes (10%), which are characteristic of the Boreal and Hypo-Arctic zones of the Palearctic, dominate. The zoogeographic originality of the local avifauna is due to the combination of elements of the Far Eastern–island, Pacifical, Siberian, and Chinese faunal complexes; Siberian–American and widespread species; and Japanese island endemics. The avifauna of Urup Island is formed in the system of general zonal-landscape and altitude-belt patterns combining ecological groups of marine, land, and mountain species. Mountain specifics of the avifauna are defined by the species (n = 9), which are ecologically closely related to land or water–near-water elements of the alpine landscape over the entire area of their range or a significant part of it. The bird population density of land habitats is 323‒609 sp/km² (on average 466 sp/km²); on the coast and nearby sea area, it is 774–2050 sp/km² (on average 1412 sp/km²). The similarity coefficients of bird populations are 20% in land-based habitats and 17% in the coastal-marine habitats. The population of forest and bush habitats is dominated by the Pacific swift, buff-bellied pipit, Arctic warbler, Eurasian nutcracker, and gray bunting. The population in the coast and the adjacent sea area is dominated by the harlequin duck, glaucous-winged gull, black-legged kittiwake, Pacific swift, buff-bellied pipit, and black-backed (White) wagtail. In open sea areas, the most common species are the black-footed albatross and Laysan albatross, northern fulmar, short-tailed shearwater, common murre, and tufted puffin.