Behavioural ecology of lesser sheathbills Chionis minor at Marion Island

Includes bibliographical references.Adaptations to island life have seldom been studied in birds outside temperate or tropical regions. Lesser Sheathbills Chionis minor (Charadriiformes; Chionididae) were studied at Marion Island (46°54'S, 37°45'E) and the ways in which their feeding ecology, breeding biology and social behaviour were adapted to existence on a sub-Antarctic island were assessed. The birds' reproductive output and post-fledging survival rates were estimated and probable factors limiting the population examined. Seasonal and spatial variations in the diet and foraging habits were related to the quality, availability and distribution of food, and the effects of interspecific competition, the weather and predators. The adaptiveness of the broad trophic niche was investigated. A hypothesis that the variable social behaviour facilitated exploitation of variable food resources to benefit individual birds was examined; particular attention was paid to territoriality among breeding (summer) and non-breeding (winter) adults within penguin colonies and flocking amongst birds foraging on the coastal plain. Time and energy budgets of birds feeding in these habitats were drawn up. Displays by Lesser Sheathbills were described and their functions in territories, flocks, at nest sites and in sexual interactions were quantitatively assessed