POPULATION DEVELOPMENT AND CHANGES IN WINTER SITE USE BY THE SVALBARDLIGHT-BELLIED BRENT GOOSE, BRANTA-BERNICLA HROTA 1980-1994

The Svalbard breeding population of light-bellied brent goose Branta b ernicla hrota, wintering ill 4-5 sites in Denmark and at Lindisfarne i n north-east England, increased from c. 3500-4000 in the early 1980s t o 4000-5800 in the early 1990s. The increase was mainly due to years w ith good breeding success, but probably also to improved survival in m ild winters. Thus, in cold winters it was observed that mortality, of at least first-winter birds, increased. Major changes ill winter site use were observed during the 1980s; the use of the Danish Wadden Sea d ecreased, and in consequence, the brent geese arrived earlier at Lindi sfarne and at the main winter site, Mariager-Randers Fjords. In the co urse of winter the population now disperses to more sites and new wint ering sites have been established; in spring the majority of the popul ation is concentrated in two sites in north-west Jutland in Denmark. T he changed pattern of movement reflects decreases in distribution of Z ostera food resources and depletion of the remaining resources due to waterfowl grazing, which may negatively affect condition of the geese in winter and ultimately survival. On the other hand, the population i s now more dispersed during winter and hence less vulnerable to local environmental pertubations. The wider dispersal and changed phenology have several implications for management of the population which are d isclosed. (C) 1998 Elsevier Science Ltd. All rights reserved.