noun
tundra swan; Bewick's swan; whistling swan
Refers to the species Cygnus columbianus, a migratory swan seen in Japan in winter. The name コハクチョウ is the standard Japanese common name.
冬になると、コハクチョウが日本に飛来します。
In winter, tundra swans migrate to Japan.
あの湖でコハクチョウの群れを見ました。
I saw a flock of tundra swans at that lake.
オオハクチョウ (whooper swan) is a larger swan species also seen in Japan; コハクチョウ is smaller with a different bill pattern.
Compound of 小 (ko, 'small') + 白鳥 (hakuchō, 'swan'), literally 'small swan', referring to its smaller size compared to the whooper swan.