[Classification of the avian summer population of the Western Siberian plain]

The proposed classification system reflects the difference between the three population systems: unbuilt land, built-up land, and aquatic-semiaquatic communities. Two superorder groups--north and median--further divided into types were recognized in each of the systems. Most types are divided into subtypes, classes, and subclasses (and sometimes genera of the population). The estimation of the power and generality of the influence of environmental factors (their variability correlates with heterogeneity of the avian population) has demonstrated that forestation of the territory is most significant in the first half of summer on the western Siberian Plain. The composition of the forest-forming species and zoning are less affected. The influence of moisture and hydration is 2-3 times less significant; mesorelief is 4-5 times less significant; and productivity (feeding capacity) and anthropogenic influence are 7-9 times less significant.