Breeding Biology of the Eurasian Nuthatch in Northeastern Siberia

AnsTn.Kr. -The breeding biology of Eurasian Nuthatches (Sitta europaea asiatica) was studied in 1986-1990 in two habitats, riparian and upland forests, in the Magadan region, northeastern Siberia. Clutch sizes and breeding success averaged 6.49 eggs and 57.5%, respectively, and varied among years. Habitat influenced clutch size but not numbers of young fledged from successful nests. Within seasons, date of first egg was correlated negatively with clutch size, while in years in which breeding started later, nuthatches laid significantly larger clutches. Female age had a significant effect on the timing of the start of breeding, whereas neither female nor male age influenced clutch size or number of fledglings. Mass of young at the time of fledging was independent of brood size. The yearly mean brood size correlated positively and significantly with mean yearly nestling growth rate and mean body mass of nestlings at 18 days of age. Received 22 Sept. 1992, accepted 12 Feb. 1993.