noun
Refers specifically to the bird species Cygnus atratus. Used in both everyday and scientific contexts.
公園の池に黒鳥が一羽いる。
There is a black swan in the park pond.
黒鳥はオーストラリア原産の鳥です。
The black swan is a bird native to Australia.
白鳥 means 'swan' in general, typically a white swan, while 黒鳥 specifically refers to the black swan species.
Compound of 黒 (black) and 鳥 (bird). The reading こくちょう is the on'yomi of the kanji.