THE BREEDING PERFORMANCE OF THE GENTOO PENGUIN PYGOSCELIS-PAPUA AT THE NORTHERN EDGE OF ITS RANGE

Gentoo Penguins Pygoscelis papua on the Crozet Islands have a unique timing of breeding, which occurs in winter and is considerably protracted, differing greatly from that of other populations breeding south of the antarctic convergence. Their biology was intensively studied in 1983-1989, involving daily observations in 1983-1985. Winter breeding is associated with an extension of laying, chick rearing, foraging trips and premoult periods, a lower breeding success and a high weight loss. Annual variations in breeding performances were less pronounced than for southern populations. Variations in breeding success were closely associated with variations in feeding frequencies, fledging and breeding weight, and timing of laying. Early breeders were at an advantage over late breeders in terms of breeding success, growth patterns, fledging weight, duration of foraging trips and premoult period. The unusual winter breeding coincides with a time when food is most readily available for chick rearing in restricted foraging conditions at the edge of the species' breeding range.