The differences in plumage of a Blue Grosbeak, from top to bottom, between a breeding male (alternate plumage) a non-breeding male (basic plumage), a female and a related Indigo Bunting

Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. Blue Grosbeak ( Passerina caerulea, formerly Guiraca caerulea)* is a medium-sized Seed -eating Bird in the same family as the Northern The Indigo Bunting, Passerina cyanea, is a small Seed -eating Bird in the family Cardinalidae Feathers are one of the epidermal growths that form the distinctive outer covering or Plumage, on Birds They are considered the most complex integumentary structures Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a number of different colour morphs. Differences in plumage are used by ornithologists and birdwatchers in order to distinguish between species and collect other species specific information. Ornithology (from Greek ὄρνις ὄρνιθος ornis, ornithos, "bird" and λόγος logos, "knowledge" is the branch of Birdwatching or birding is the observation and study of Birds with the naked eye or through a visual enhancement device like Binoculars.

Basic and alternate plumage

Almost all species of birds moult at least annually, usually after the breeding season. In Biology, moulting (or molting, also known as shedding or for some species Ecdysis) signifies the manner in which an animal routinely This resulting covering of feathers, which will last either until the next breeding season or until the next annual moult, is known as the basic plumage. Many species undertake another moult prior to the breeding season known as the pre-alternate moult, the resulting breeding plumage being known as the alternate plumage. The alternate plumage is often brighter than the basic plumage, for the purposes of sexual display, but may also be cryptic in order to hide incubating birds that might be vulnerable on the nest. ^[1] Many ducks have bright, colorful plumage, exhibiting strong sexual dimorphism to attract the females. Sexual dimorphism is the systematic difference in form between individuals of different Sex in the same Species. However, they moult into a dull plumage in the non-breeding season. This drab female-like appearance is the eclipse plumage. When they shed feathers to go into eclipse, the ducks become flightless for a short period of time. Some duck species remain in eclipse for one to three months in the summer, while other would retain the cryptic plumage until the next spring when they undergo another moult to return to their fancy breeding garb.

Abnormal plumage

There are hereditary as well as non-hereditary variations in plumage that are rare and termed as abnormal plumages. These include excessive dark pigmentation or melanism, lack of pigmentation ranging from leucism to albinism, presence of excessive red or yellow pigmentation leading to, respectively, erythrism or xanthochroism. There can also be polymorphism in some birds particularly the owls and cuckoos where certain colour variations are more widespread and examples of these include the hepatic forms of cuckoos. The Owls are an order of birds of prey. Most are Solitary, and nocturnal, with some exceptions (e The cuckoos are a family Cuculidae, of Near passerine Birds The order Cuculiformes, in addition to the cuckoos also includes the

Such abnormalities can be present throughout the bird or restricted to specific feather tracts.

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