noun
brent goose; brant goose
Refers specifically to the species Branta bernicla, a small dark goose. Usually written in katakana as コクガン.
コクガンは冬に日本へ渡ってくる。
Brent geese migrate to Japan in winter.
The name コクガン (黒雁) literally means 'black goose', from 黒 (black) and 雁 (wild goose). The exact historical derivation is uncertain, but the name likely describes the bird's dark plumage.