Reproductive parameters of four thrush species of Central Siberia

In a stable population, the productivity of reproduction (the number of offspring a pair produces per season) compensates for the annual death rate, which depends on the conditions in both the nesting habitat and the wintering sites. Adaptations of species for survival during the entire yearly cycle determine not only the general result of reproduction but also the various ways of achieving it. Populations of four thrush (Turdus, Zoothera) species are compared in this study. Their differences in the size of the clutch, success of nesting, duration of the season and of the nesting cycle, and thus, their contribution to the general result of reproduction over the season were discussed.