The behaviour, ecology and energetics of the East Canadian High Arctic light-bellied brent goose (Bronto bernicla hrota) was investigated to determine winter feeding Site selection on Strangford Lough, Co Down, Northern Ireland. The seasonal use of mudflats, saltmarsh and improved pasture was assessed to evaluate the role these habitats play in fulfilling the energy requirements of the geese throughout the wintering period. Brent geese began feeding on eelgrasses Zostera spp. on arrival in late August early September. Single adults arrived first and were in poorer physical condition than paired or family adults which arrived later. Differences in distribution of feeding and physical condition suggests that families are more able than paired or single birds to maintain access to a better quality/quantity food supply over the winter. The activity budget and net energy results highlight the importance of Zostera spp. and the energetic constraints faced by brent geese feeding on Zostera spp. over winter. Position-sensitive radio telemetry provided an accurate and effective method for determining the time spent feeding by individual brent geese throughout the 24hour period in late winter early spring. At this time brent geese rely heavily on the contribution from improved pasture in order to meet their daily net energy . requirement prior to spring migration. Brent geese engaged in night time feeding, exclusively on the mudflats. Night-time feeding occurred from October to April, peaking in mid-winter. This activity appears to be a strategy for the geese to meet their energy requirements during shorter, colder winter days. Feeding on saltmarsh vegetation occurs subsequent to the depletion of Zostera spp. and at a critical time in mid winter and is constrained by the availability and quality, rather than quantity, of the food resource. The study's findings would suggest that for the future conservation of the geese the main conservation requirements for the population is the maintenance of intertidal habitat quality together with the creation of inland refuaes in areas where there may be conflict with agricultural interests.