Breeding Biology of the Pigeon Guillemot in the Chukotka Peninsula, Russia

Abstract

-The breeding biology of the Pigeon Guillemot (Cepphus columba) was studied at Cape Ulyakhpen, the Chukotka Peninsula, Russia, in 1988-1990. In 1989 the bulk of Pigeon Guillemot population arrived in the vicinity of the colonies on the south coast of the peninsula in late April. In 1989 and 1990, the median dates of laying, hatching and fledging were 23 and 20 June; 20 and 17 July; 25 and 19 August, respectively. The average clutch size was 1.77 ? 0.42 eggs, with the average egg dimensions, 61.2 ? 2.1 mm and 41.1 ? 1.3 mm. Replacement clutches were initiated on average 12.3 ? 0.8 days after losing the first clutch. During incubation eggs lost on average 15.2 ? 0.4 per cent of their initial mass. Chicks averaged 39.2 ? 3.7g at hatching and 402.4 ? 40.9 g. at fledgling (87.2% of adult mass). Chicks left their nests at the age of 36.3 ? 2.8 days. Chick mass at fledging showed no significant intraand interannual variation. Received 14January 1998, provisionally accepted 13 March 1998, accepted 20June 2000.