Biology of the greenish warbler Pylloscopus trochyloides (Passeriformes, Sylvidae) from Karelia [Russian]

摘要

The data on greenish warbler were collected mainly in southern Karelia in 1974-2001. The main nesting area of this bird is Asia and Eastern Europe; in Central and Western Europe it nests rarely. The species has been known within the former Olonets province since 1974, but the author found the first nest in 1974. Since that time, this bird's nests were recorded regularly in this area. The population density varies in different habitats: from 0.7 pairs/km(2) in mature pine forests to 40 pairs/km(2) in middle-aged and maturing mixed ones. Greenish warbler arrives to southern Karelia in May (May 13, 1981-June 2, 1987), the mass arrival takes place within the first ten days of June. Nests are built in different habitats, but places littered with wind-fallen trees and strongly damped are more attractive for the birds. Nests are located at the altitudes of 0-180 cm above soil surface (41.5 +/- 3.3 cm, n = 121). The period of egg laying extends from May 30 to July 12, but in most cases breeding begins in early June. The number of eggs in a clutch is 4-7 (average is 5.8 +/- 0.1, n = 130). Brood size varies from 0 to 7 nestlings (average is 4.9 +/- 0.1, n = 130); 12.4% of the nests are fully lost. The size of clutch and brood decreases by the end of nesting seasons. The survival of brood in greenish warbler is higher than in the related species. On average, it is 83.4 +/- 1.4% (n = 124) for a nesting period. The main cause of egg losses in nesting periods is predators. In northwestern Russia, postjuvenile molt is absent, but postbreeding one is partial. Most adult birds studied begin to molt even during feeding of nestlings. In early August all young and adult birds leave the areas of nesting.