The Brent Goose (Branta bernicla) is a goose of the genus Branta, known in North America as Brant. The spelling “Brant” is the original one, with “Brent” being a later folk-etymological idea that it was derived from a classical Greek waterbird name brenthos. It is in fact onomatopoeic, derived from the guttural call note of the species.
This small goose measures about 60 cm long and sports a short, stubby bill. The short tail (the shortest of any goose) is pure white underneath and black on top.
It used to be a strictly coastal bird in winter, seldom leaving tidal estuaries, where it fed on eel-grass (Zostera marina) and a type of seaweed, sea lettuce (Ulva). In recent decades, it has started using agricultural land a short distance inland whre they feed extensively on grass and winter-sown cereals. This may be behavior learned by following other species of geese. Food resources pressure may also be important in forcing this change, as the world population has risen over ten-fold to 400-500,000 by the mid 1980s, possibly reaching the carrying capacity of the estuaries.
During the breeding season, it can be found in low-lying wet coastal tundra. The bowl-shaped nest is constructed in and elevated location, such as small ponds and is lined with grass and down.
Brent Goose has three subspecies:
- Dark-bellied Brent Goose Branta bernicla bernicla
- Pale-bellied Brent Goose Branta bernicla hrota (sometimes also known as Light-bellied Brent Goose in Europe, and Atlantic Brant in North America)
- Black Brant Branta bernicla nigricans
Some DNA evidence suggests that these forms are genetically distinct; while a split into three separate species has been proposed, it is not widely accepted, with other evidence upholding their maintenance as a single species.
The body of the Dark-bellied form is mostly dark grey-brown all over, the flanks and belly slightly paler than the back. The head and neck are black, with a small white patch on either side of the neck. It breeds along the Arctic coasts of central and western Siberia and winters in western Europe, with over half the population in southern England, the rest between northern Germany and northern France.
The Pale-bellied Brent Goose appears blackish-brown and light grey in color. The body is varying shades of grey-brown all over. The flanks and belly are significantly paler than the back and present a marked contrast. The head and neck are black, with a small white patch on either side of the neck. It breeds in Franz Josef Land, Svalbard, Greenland and northeastern Canada, wintering in Denmark, northeast England, Ireland and the Atlantic coast of the U.S. from Maine to Georgia.
The Black Brant is blackish-brown and white in color. This form is a highly contrasted black and white bird with a uniformly dark sooty-brown back, similarly-colored underparts (with the dark color extending furthest back of the three forms) and a prominent white flank patch. It also has larger white neck patches which form a near-complete collar. It breeds in northwestern Canada, Alaska and eastern Siberia, and wintering mostly on the west coast of North America from southern Alaska to California, but also some in east Asia, mainly Japan.
The Asian Black Brant populations had previously been thought to be a separate subspecies, orientalis, based on supposed paler upperparts coloration; however, it is generally now believed not that this is not correct.
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 yet, for a population of birds breeding in central arctic Canada (mainly Melville Island), and wintering in the 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 Brent, having brown upperparts and grey underparts which give less of a contrast with the white flank patch. Given that this population exhibits mixed characters, it has also been proposed that, rather than being a separate subspecies, it is actually a result of interbreeding between these two forms.