nuptial plumage

…In birds, the males often wear very flamboyant feathers during the molting process before the breeding season. This is also a type of nuptial coloration, but since it is not simply skin coloration, it is specifically called nuptial plumage. It has been experimentally confirmed that the testes develop and mature with the onset of the breeding season, which results in increased secretion of male hormones, resulting in changes in pigmentation and feather formation, resulting in the development of nuptial coloration and nuptial plumage.

*Some of the terminology that mentions "nuptial plumage" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…鳥類では，繁殖期に入る前の換羽によって，雄がしばしばきわめてはでな羽毛をまとうものが多い。これも婚姻色の一種であるが，単なる皮膚の着色ではないためとくに婚衣nuptial plumageとよばれる。　繁殖期の到来に伴って精巣が発達，成熟し，その結果雄性ホルモン分泌がさかんとなって，色素形成，羽毛形成に変化が起こり，婚姻色や婚衣が生ずることは，実験的にもたしかめられている。…

※「nuptial plumage」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報