Secondary contact and overlap of Parus major and Parus minor populations in the middle Amur River basin

摘要

A revision of situation in the zone of overlapping (OZ) of Parus major and P. minor populations in the middle Amur River basin was performed based on the field studies (1991-1996) and available literature. Dimensions and shape of OZ were determined for the first time. Its total range is about 250 km. Human settlements are typical habitats of P. major, secondary broad-leaved forests in the vicinity of these localities are populated by P. minor. The most sustainable state of interaction between the populations major and minor is their co-existence in human settlements, where local and limited hybridization takes place in a narrow belt of populations' contact. This is true for the central part of OZ. In eastern OZ. where both populations inhabit settlements, mixed populations exist; there is a tendency of displacing minor forms out of human settlements (Birobidzan city). The populations are shown to come in contact 100 years ago as a result of their dispersal due to transformation of the environment because of human activities.