DEMOGRAPHY OF FICEDULA-HYPOLEUCA (PASSERIFORMES, MUSCICAPIDAE) IN SOUTHERN PART OF ITS RANGE

Demography of the pied flycatcher (Ficedula hypoleuca) was studied in southern Karelia in 1979-1996. The age structure of this population di d not differ from that in other parts of the range. Mortality was 47% in adults and 80% in young birds. The average expected duration of lif e is 1.6 years. There is no selection of partners by age. 9% of the bi rds kept the former partner during two seasons. Bigamy is registered i n 5.8% of males (from 2 to 17% in a year). The hypothesis of the best genetic qualities of bigamous males is denied. Two-year-old females la y their eggs earlier and have greater clutches than one-year-old ones. Pairs with two-year-old males start reproduction earlier than ones wi th one-year-old males. Despite the birds of different age have no gain in the numbers of fledglings. In Karelia age differences in reproduct ion are displayed only in seasons with early warm springs. The equatio n of regression describing with sufficient accuracy (p = 0.01) the dyn amics of bird numbers in the controlled area (y): y = 1.18x(1) + 0.09x (2), where x(1) - number of coming back males (%), x(2) - maximum numb ers in autumn of the previous season. Significant annual fluctuations in the population numbers are mainly related to the level of bird mort ality beyond the reproduction period.