collective feathered covering of a bird. It provides protection, insulation, and adornment and also helps streamline and soften body contours, reducing friction in air and water. Plumage of the newborn chick is downy, called neossoptile; that which follows is termed teleoptile. Juvenal plumage, frequently distinct from that of the adult bird, is often drab, streaked, or spotted and thus camouflages the young.

Sexual differences are common, the plumage of the male characteristically showing more brilliance and pattern than that of the female. Feathers are normally lost and replaced at least once a year through molt and regrowth. Eclipse plumage, typical of ducks but found in other birds as well, is dull, female-like plumage worn by the male for a month or more in summer after breeding. It “eclipses” his usual bright plumage. He soon molts and is flightless until he grows new wing feathers. Compare pelage.