Crest (feathers)

The crest is a prominent feature exhibited by several bird species on their heads. It is distinct from features such as casques and cockscombs - sometimes erroneously referred to as "crests", which are bony and fleshy structures respectively.

The crest is made up of semiplume feathers: a long rachis with barbs on either side. These are plumulaceous feathers, meaning that they are soft and bendable. In birds, these semiplumes are common along the head, neck, and upper back, and may be used for buoyancy and sensing vibrations.

Crests on birds are generally used for display purposes. Cockatoos (a family that also includes corellas and the cockatiel) are part of the parrot family Cacatuidae found in Australia, the Bismarck Archipelago and the Philippines, and are probably the most recognizable birds to feature crests.^[1]Cockatoos and cockatiels possess crests which may be raised or lowered at will. Their crests are used to communicate with fellow members of their species, or as a form of defense to frighten away other species that approach too closely, making the bird appear larger when the crest is suddenly and unexpectedly raised.^[2]

Crests can be recumbent or recursive, depending on the species.^[3] The recumbent crest has feathers that are straight and lie down essentially flat on the head until the bird fans them out to where they stand up. The white cockatoo, for example, possesses a recumbent crest.^[3] The recursive crest is noticeable even when it is not fanned out because it features feathers, that, when lying down, curve upward at the tips, and when standing up, often bend slightly forward toward the front of the head. Many recursive crests also feature brilliant colors. The sulphur-crested cockatoo has a recursive crest, and the Major Mitchell's cockatoo (also known as the Leadbeater's cockatoo) possesses a prominent recursive crest.^[2] Some birds, like the galah, or rose-breasted cockatoo, have modified crests, which has features of both recumbent and recursive types.^[2]

多くの家禽類は冠羽を持っています。^{[ 4 ]}これらの構造には、選択育種または突然変異という2つの起源があることが知られています。家禽類の冠羽は、種によって形態に幅広いバリエーションがあります。家禽類の冠羽形成に関わる分子および遺伝的メカニズムは十分に解明されていません。そのため、冠羽は形態学的研究やその他の関連する生物学的分野、特に家禽類に関して広く研究されています。^{[ 5 ]}

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  キバタン（Cacatua citrinocristata）の冠羽（1cm グリッド上）
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  ミッチェルオウム( Cacatua leadbeateri )
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  冠羽を立てたオウム（Cacatua alba）
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  冠羽を立てたメスのモモイロインコ（Eolophus roseicapilla）
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  オカメインコ( Nymphicus hollandicus )
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  ビクトリア冠鳩（Goura victoria）
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  インドクジャク（Pavo cristatus）
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  タゲリ（Vanellus vanellus）
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  マカロニペンギン（Eudyptes chrysolophus）
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  オスのオシドリ（Aix galericulata）
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  ヤツガシラ( Upupa epops )

冬から夏へ

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  冬期のコサギ（Egretta garzetta ）、冠羽なし
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  夏期のコサギ（冠羽あり）
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  冬期のカンムリカイツブリ（Podiceps cristatus ）、冠羽は小さくなっている。
• 
  夏期のカンムリカイツブリ、完全な冠羽を持つ

• 櫛（解剖学）
• 冠ペンギン
• スヌード（解剖学）
• ワトル（解剖学）