noun
whooper swan
A large migratory swan species (Cygnus cygnus) found in northern Eurasia; winters in Japan. The katakana name is standard in field guides and everyday use.
冬になると、オオハクチョウが日本に飛来する。
In winter, whooper swans migrate to Japan.
あの湖でオオハクチョウの群れを見た。
I saw a flock of whooper swans at that lake.
The tundra swan (Cygnus columbianus), a smaller species with a different bill pattern; also winters in Japan.
From 大 (おお, 'large') + 白鳥 (はくちょう, 'swan'). The katakana spelling follows the convention for Japanese bird names.