Forest biogeocenosis is a necessary environment for the normal existence of many species of wild animals, including birds. Recently, however, a gradual decrease in their numbers is observed in most forest areas of the Forest-Steppe zone. This indicator is one of the most important criteria for estimation of the general condition of this or that ecosystem. In this regard, specialists-zoologists, ornithologists, etc. pay great attention to the study of this issue (Koval' N.F. 1982). Currently, there is a quite extensive and often conflicting material regarding the number of birds. The most fundamental is the book by D. Lack, “The number of animals and its regulation in nature” (1957), which shows the influence of the food supply, the number of nesting places, “shelters”, and enemies on the reproductive ability, survival and general dynamics of the number of many bird species. Determining the breeding intensity of specific species populations of bird, we proposed to use the so-called productivity coefficient, which allows us to compare both the degree of biomass stability over the breeding period during a number of years and its geographical differences. The total number of birds on nesting can be different in various parts of the range under the influence of environmental conditions. The number of birds nesting on the ground and in the underwood has recently decreased significantly due to the large recreational burden of forest cenoses. Consideration of the dynamics of the number of daytime predatory birds and owls is of special attention. Their numbers have recently stabilized, although it continues to decline in some regions according to the available literary data. Ornithologists consider this mainly as a consequence of environmental pollution, killing of birds by humans, destruction of their habitats. The number of animal populations, for example, can vary significantly during the year or on average over the years. It is determined by the breeding rate and mortality of individuals. The breeding rate of birds is directly dependent on the size of egg laying, the success of eggs brooding and the percentage of flying out of viable young animals, which in total determines the success of breeding.