Age of First Pairing and Breeding among Greenland White-Fronted Geese

Abstract

The Greenland White-fronted Goose (Anser albifrons flavirostris) breeds in west Greenland and winters in Britain and Ireland (Salomonsen 1950). The population fell from 17,500-23,000 in the 1950s to 14,30016,600 by the late 1970s (Ruttledge and Ogilvie 1979) and is currently estimated to be 26,700 as of November 1989 (Warren 1990). Due to its scattered wintering distribution and low productivity, this sub-species remains threatened in western Europe and there is a need to model population processes in order to provide a firm basis for conservation management. Fundamental to our understanding of the population processes amongst such long lived individuals are data relating to age-specific breeding success and survival (Owen 1980, Raveling 1981). Age of first pairing and breeding is likely to be one of the most important determinants of goose population productivity (Boyd 1956). The proportion of young in the Greenland Whitefronted Goose population each winter is low when compared with other races ofAnser albifrons, although clutch size and consequently brood size tend to be greater (Owen 1980, Fox and Stroud 1988). Egg predation appears to be a major factor influencing nesting success (Fox and Stroud 1988). Hence, the population seems to be characterized by relatively few pairs returning to the wintering grounds with young each year. Using a population of individually marked birds, we attempted to assess whether the low proportion of successfully breeding pairs of Greenland White-fronted Geese is due to deferred breeding.