BILT E VAN DER & HELMING B (1978) The winter-ecology of the Brent Goose Branta bernicla on Terschelling. LIMOSA 51 (1): 31-40.

From September 1974 until June 1975 the authors studied several aspects ofthe ecology of the Brent Goose Branta bernicla on Terschelling. During this time they could distinguish three periods. (I) In autumn the Brent Geese foraged mainly on the mud-flats. They fed mainly on Enteromorpha sp. The portion of Eelgrass Zostera noltii in the total food-intake was less than 15% (Braster & Carriere 1976). As the days shorten, the forage-activity Fd increased at the cost of the time spent on resting and preening (Fig. 4). At the end of November the majority of the Brent Geese left Terschelling. A flock of about II ()() geese wintered on the island. (2) The wintering Brent Geese mainly used the grass in the polders for food. The shortening of the days and the fall of temperature forced them to forage most of the day. Between 12 December and 10 January they spent 95% of the forage-day on feeding, watching and walking. At the half of January the Brent Geese were able to spend more time on resting and preening on the mud-flats. Until the middle of March the forage-activity in the polders made about 80% of the total activity (Fig. 6). Because of the more frequent and longer periods of rest, the forage-activity during the day decreased while the length of the day increased. (3) In spring the Brent Geese fed mainly on the tidal marshes (Fig. 2 & 3). The forage-activity during daytime (Fd) was as high as in December/January, about 84% of the total activity. There are however 13 hours instead of 7 in December/January to spend on feeding. The daily food-intake should exceed the metabolic required quantity of food if the foodvalue of the plants taken is about the same as from the plants the geese fed on in winter. During spring the Brent Geese have to build up there fat-supply in order to fly successfully to their arctic breeding grounds. Dark-bellied Brent Goose Branta bernicla

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