天鹅：修订间差异

天鹅属的鸟雌雄同色，雌性略小于雄性。<ref name=wildfowl/>天鹅的体形较大且脖颈修长，不同种喙的颜色有明显的差异，疣鼻天鹅和黑颈天鹅的[[鳥喙|喙]]基部有明显的突起。<ref name=ani-black/><ref name=bto-mute/><ref name=ani-black-neck>{{Cite web|last=Urdarevik|first=Dragana|title=Cygnus melancoryphus (black-necked swan)|url=https://animaldiversity.org/accounts/Cygnus_melancoryphus/|access-date=2023-09-11|website=Animal Diversity Web|language=en|archive-date=2023-12-09|archive-url=https://web.archive.org/web/20231209072736/https://animaldiversity.org/accounts/Cygnus_melancoryphus/|dead-url=no}}</ref>大天鹅、小天鹅喙上的黄色与黑色在不同的年龄也会有变化。<ref name=ani-whooper/>天鹅的身体呈两头尖的[[椭圆形]]，腿较短，脚黑色。<ref name=bto-mute/>本属的鸟颜色特征明显，北半球的天鹅物种羽毛纯白色，但南半球的物种则黑白相间。<ref name=ani-black/><ref name=ani-black-neck/>澳大利亚的[[黑天鹅]]（''Cygnus atratus''）除了翅膀上的白色的初级飞羽外，全身都是黑色的；黑天鹅的幼雏是浅灰色的。<ref name=ani-black/>南美洲的[[黑颈天鹅]]有着白色的身体和黑色的脖子。<ref name=ani-black-neck/>亚成体的羽色黯淡，且嘴的颜色不像成鸟的那么鲜艳。<ref name=ani-black-neck/>幼鸟体羽多灰褐色，俗称丑小鸭。<ref name="Madge">{{Cite book |last1=Madge |first1=Steve |last2=Burn |first2=Hilary |title=Waterfowl: An Identification Guide to the Ducks, Geese, and Swans of the World |publisher=Houghton Mifflin |year=1988 |location=Boston |isbn=978-0-395-46727-5 |url-access=registration |url=https://archive.org/details/waterfowl00stev |language=en}}</ref>