Plumage

Plumage is the collective set of feathers that covers a bird’s body. Feathers are keratinous structures grown from follicles; a feather includes a calamus (the shaft embedded in the skin), a rachis, barbs, and barbules that interlock to form the vane. The colors and patterns of plumage arise from pigments and from microstructures that produce structural coloration.

Pigments such as melanin produce blacks, grays, and browns; carotenoids (obtained through diet) yield reds, oranges, and yellows; and pteridines can add additional hues. Many birds also display iridescent or ultraviolet colors produced by nanoscale structures within the feather barbules, which interact with light in ways visible to birds and, in some cases, to humans.

Plumage varies with age, season, and molt. Many species have juvenile or immature plumage distinct from the adult. Plumage is regularly replaced through molting: prebasic molts produce the basic (often nonbreeding) plumage, while prealternate molts yield brighter breeding plumage in some species. Some ducks and related birds exhibit an eclipse phase during which breeding plumage is temporarily replaced by a dull, nonbreeding appearance.

Functions of plumage include camouflage, signaling and mate choice, species recognition, and social signaling. Plumage also contributes to insulation and waterproofing, and ultraviolet reflectance can convey information about health or quality to conspecifics. Sexual dimorphism is common, with males often displaying more elaborate or vivid plumage for displays and competition, while females tend toward cryptic coloration to aid nesting. Plumage patterns frequently reflect ecological factors such as habitat and foraging style. In ornithology, plumage is a key trait for identification, taxonomy, and studies of behavior and evolution.