The structure of nest aggregations of steppe birds in Baikalian Siberia

On the base of different types of nest aggregations was made analysis of spatial and ethological structures of nets aggregations of steppe birds in Baikalian Siberia. 382 nest aggregations 28 species of birds were analyzed. For steppe species all 4 types of nests aggregations are characteristically. The biggest part (13 species, 46.4%) belongs to species with lonely type of nesting. Procolonies were or ganized by 9(32.1%) species, just under half of them seldom nesting by singles pairs. Semicolonies (2 species, 7.1%) and colonies (4 species, 14.3%) had unusual types of nest aggregations for steppe birds. The main factor determinates types of nets aggregations, for small birds and also for big species which couldn’t protect their posterity, is safety condition. For birds of prey which are hunting to vertebrates mammals the serious meaning has fodder conditions. Most passerines characterized by the formation of groups in the form of procolonies, which provides good protection and synchronization of the timing of reproduction. Territoriality of those birds in marriage period and in the early stages of reproduction (prevent newcomers pairs colonization) assists for thinned locations of birds’ nests which increase protection and in the same time saved the visual and acoustic communication between birds in aggregation. Colonial aggregation could make only those species with well protected nests. Besides that species could but not equally collectively defend their settlements. Most species of birds the type of aggregations especially its structure is not determinated and could change in certain limits in depending from specific conditions.