Summary
This paper discusses the ecological factors that affect the populations of the Great tit (Parus major) and Japanese tit (Parus minor) in different parts of their area of sympatry and hybridization in the Amur region. The identified factors exert their effects in different directions and strength in different parts of the vast area of sympatry of these two species. It can be assumed that they have a significant effect on the maintenance of species-specific phenotypes of the great and Japanese tits.