It used to be a strictly coastal bird in winter, seldom leaving tidal estuaries, where it feeds on eel-grass (Zostera marina) and the seaweed, sea lettuce (Ulva). In recent decades, it has started using agricultural land a short distance inland, feeding extensively on grass and winter-sown cereals. This may be behaviour learnt by following other species of geese. Food resource pressure may also be important in forcing this change, as the world population has risen over tenfold to 400,000-500,000 by the mid 1980s, possibly reaching the carrying capacity of the estuaries. In the breeding season, it uses low-lying wet coastal tundra for both breeding and feeding. The nest is bowl-shaped, lined with grass and down, in an elevated location, often in a small pond.
The Brant Goose is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.