Parrot plumage has exclusive pigmentation.

The spectacular red feathers of certain parrots owe their vibrancy to a rare set of pigments found nowhere else in nature, a new study suggests.

Kevin McGraw of Arizona State University in Tempe and Mary Nogare, a parrot enthusiast in Snoqualmie, Wash., analyzed feathers from 44 species of parrots mainly from pet stores, owners' homes, and zoos.

The researchers extracted and characterized the pigments. They found that all the birds' red feathers contained a set of five pigments called polyenal lipochromes.

In other birds, a class of pigments called carotenoids, which are absent in parrot feathers, produces red coloration. Unlike carotenoids, which birds obtain from their diets, lipochromes appear to be synthesized within the follicles of maturing parrot feathers, says McGraw.

The researchers assert that the ubiquity of the lipochromes in parrot species indicates that these pigments, which cost the birds energy to produce, play an important role in the birds' survival. Given that both male and female parrots produce the same set of five pigments, McGraw says that the colors must not be important to mate choice. Instead, he hypothesizes that the pigments are necessary for distinguishing individuals of one species from another or that they may be important for camouflage.

The researchers describe their findings in an upcoming Biology Letters.