Ecological and Geographical Analysis of the Ornithocomplexes of the Tobol-Irtysh Forest Steppe and the Steppe of Western Siberia and Northern Kazakhstan in the Winter

According to the results of winter bird counts conducted in 70 habitats over 12 years, in the period from 1982 to 2002, a hierarchical classification and a structural similarity graph of ornithocomplexes in the southwestern plains of Western Siberia and Northern Kazakhstan have been compiled. The hierarchical classification contains three types and nine subtypes of the ornithocomplex. The similarity graph (the spatial-typological structure of the ornithocomplex) is built at the level of subtypes and is represented by three rows (trends). The first and most significant of these series is determined by the influence of urbanization; forest cover; and, in part, by the development of the reed layer. The second series of territorial changes in ornithocomplexes is associated with changes in the built-up area and anthropogenic fodder in residential habitats. The third row is formed under the influence of afforestation and overgrowth. The characteristics of ornithocomplex subtypes are compared which contain information on the three most numerous bird species (leaders in abundance), their share in the community, population density, and background species richness. Based on the assessment of the degree of coincidence of the similarity of ornithocomplexes and environmental factors, a hierarchy of the influence of the main anthropogenic and natural factors that determine the formation of the winter population of birds has been established. The regional specifics and seasonal changes in the significance of environmental factors in the formation of winter bird communities of the Tobol-Irtysh forest steppe and steppe have been established.