Lough Foyle, Strangford Lough, Tralee Bay and Castlemaine Harbour. The black brant B. b. nigricans appears blackish-brown and white in colour. This form is a very contrastingly black and white bird, with a uniformly dark sooty-brown back, similarly coloured underparts (with the dark colour extending furthest back of the three forms) and a prominent white flank patch; it also has larger white neck patches, forming a near-complete collar. The population of about 125000 breeds in northwestern Canada, Alaska and eastern Siberia, and winters mostly on the west coast of North America from southern Alaska to California, but also some in east Asia, mainly Japan, also Korea and China. The population has been as high as 200,000 in 1981, and as low as 100,000 in 1987. The Asian populations of the black brant populations had previously been regarded as a separate subspecies B. b. orientalis based on purported paler upperparts coloration; however, it is generally now believed that this is not correct, and they are assigned to B. b. nigricans. A fourth form (known variously as gray brant, intermediate brant, or grey-bellied brent goose) has been proposed, although no formal subspecies description has been made as yet, for a population of birds breeding in central Arctic Canada (mainly Melville Island), and wintering on Puget Sound on the American west coast around the U.S./Canada border. These birds are intermediate in appearance between black brant and pale-bellied brant, having brown upperparts and grey underparts which give less of a contrast with the white flank patch. It has also been proposed that, rather than being a separate subspecies, it is actually a result of interbreeding between these two forms, given that this population exhibits mixed characters. Individual birds when wintering generally remain in loose family-groups, together with others of the same sub-species, but there is overlap in some areas (for example Western Europe, see above); and this is also true in the breeding colonies. Outside the breeding season, individuals with characteristics of any subspecies may occasionally turn up with regular migrants, and there has been debate as to whether this is related to migration routing accidents, or to breeding range overlap, or even interbreeding. Habitat The brant goose was strictly coastal bird in winter, rarely leaving tidal estuaries, where it feeds on eelgrass (Zostera marina) and the seaweed, sea lettuce (Ulva). On the east coast of North America, the inclusion of sea lettuce is