Plumage

Plumage (from Latin pluma 'feather') is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with sex and age classes. Within a few species, there can be different colour morphs. The placement of feathers on a bird is not haphazard but rather emerges in organised, overlapping rows and groups, and these feather tracts are known by standard names.

Most birds moult twice a year, resulting in a breeding plumage and a non-breeding plumage; one of the moults, usually the one just after breeding, is a complete moult replacing all the feathers; the other, usually the one just before breeding, is often only a partial moult, with new small body feathers but not replacing the larger flight feathers in the wings and tail. Some very large birds, like eagles, replace their flight feathers slowly but continuously throughout the year, to minimise loss of flight efficiency. Many ducks and some other species such as the red junglefowl have males wearing a bright plumage while breeding and a drab eclipse plumage for some months afterward. Many passerine species have only one moult per year, with changes in plumage resulting from the wear of differently-coloured feather tips. Young birds have a juvenile plumage, which is replaced in the months after fledging by the first-winter plumage; in long-lived birds with slow maturation like gulls, this is followed by a succession of second, third, and sometimes fourth year immature plumages.

Plumology (or plumage science) is the name for the science that is associated with the study of feathers.

Many male ducks in the family Anatidae have bright, colourful plumage, exhibiting strong sexual dimorphism. However, they moult into a dull plumage after breeding in mid-summer. This drab, female-like appearance is called eclipse plumage. They shed all their flight feathers simultaneously when in eclipse, becoming flightless for a short period. Some duck species remain in eclipse for one to three months in the late summer to early winter, while others retain the cryptic plumage until the next spring when they undergo another moult to return to their breeding plumage.

Although mainly found in the Anatidae, a few other species, including red junglefowl, most fairywrens^[a] and some sunbirds also have an eclipse plumage. In the superb and splendid fairywrens, very old males (over about four years) may moult from one breeding plumage to another whereas in the red-backed and white-winged fairywrens, males do not acquire breeding plumage until four years old, well after they become sexually mature and indeed longer than the vast majority of individuals live.

In contrast to the ducks, males of hummingbirds and most lek-mating passerines – like the Guianan cock-of-the-rock or birds of paradise – retain their exuberant plumage and sexual dimorphism at all times, moulting as ordinary birds do once annually.

In some birds, including many true owls (Strigidae), some nightjars (Caprimulgidae), some skuas (Stercorariidae), and a few cuckoos (Cuculus and relatives) being widely known examples, there is colour polymorphism in plumage. This means that two or more colour variants occur within their populations during all or at least most seasons and plumages; in the above-mentioned examples a brown (phaeomelanin) and grey (eumelanin) morph exist, termed "hepatic form" particularly in the cuckoos. Other cases of natural polymorphism are of various kinds; many are melanic/nonmelanic (some paradise-flycatchers, Terpsiphone, for example), but more unusual types of polymorphism exist – the face colour of the Gouldian finch (Erythrura gouldiae) or the courtship types of male ruffs (Calidris pugnax).

The Humphrey–Parkes terminology is a naming system developed by a small group of ornithologists in the USA, using its own specialist names for plumages. The annual moult after the breeding season, is known in it as the pre-basic moult. 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 before the breeding season known as the pre-alternate moult, the resulting breeding plumage being known as the alternate or nuptial plumage. The alternate plumage is often brighter than the basic plumage, for sexual display, but may also be cryptic to hide incubating birds that might be vulnerable on the nest.