Dispersal history and current breeding range of the Mute Swan (<i>Cygnus olor</i>, Anatidae, Aves) in northwestern Russia

Throughout the 20th century and the first decades of the current century, the Mute Swan, Cygnus olor, has been growing in numbers and expanding its range both northward and northeastward. The history of the species’ settlement to the Northwest of Russia and the main stages of its expansion, as well as the peculiarities of its spatial distribution in the region are discussed. The Mute Swan started breeding in northwestern Russia in the mid-1980s. The species settled in two landscapes: on shallow eutrophic lakes and on sea moraine and selga islands. To date, the species’ range covers the eastern part of the Gulf of Finland, the west and southwest of the Leningrad Region, the whole Pskov Region, and the westernmost parts of the Novgorod and Tver regions. It is noteworthy noting that at the initial stages of expansion the first breeding pairs appeared throughout most of the above-mentioned territories at once. Subsequently, new nests were recorded mainly within the “occupied zone” delineated by the first newcomers. During more than 30 years of expansion, the range of the species moved eastwards by no more than 88–94 km at different localities, while during the previous 20 years (1960–1980) the Mute Swan’s range in Scandinavia moved up to 998 km. Decreasing rates of range expansion amid a continued development of a warm phase of the climate suggest the presence of some kind of climatic barriers for the species in the region.