Beak - Color

Color

The color of a bird's beak results from concentrations of pigments—primarily melanins and carotenoids—in the epidermal layers, including the rhamphotheca. Eumelanin, which is found in the bare parts of many bird species, is responsible for all shades of gray and black; the denser the deposits of pigment found in the epidermis, the darker the resulting color. Phaeomelanin produces "earth tones" ranging from gold and rufous to various shades of brown. Although it is thought to occur in combination with eumelanin in beaks which are buff, tan, or horn-colored, researchers have yet to isolate phaeomelanin from any beak structure. More than a dozen types of carotenoids are responsible for the coloration of most red, orange, and yellow beaks. The hue of the color is determined by the precise mix of red and yellow pigments, while the saturation is determined by the density of the deposited pigments. For example, bright red is created by dense deposits of mostly red pigments, while dull yellow is created by diffuse deposits of mostly yellow pigments. Bright orange is created by dense deposits of both red and yellow pigments, in roughly equal concentrations. Beak coloration helps to make displays using those beaks more obvious.

Birds are capable of seeing colors in the ultraviolet range, and some species are known to have ultraviolet peaks of reflectance (indicating the presence of ultraviolet color) on their beaks. The presence and intensity of these peaks may indicate a bird's fitness, sexual maturity or pair bond status. King and Emperor Penguins, for example, show spots of ultraviolet reflectance only as adults. These spots are brighter on paired birds than on courting birds. The position of such spots on the beak may be important in allowing birds to identify conspecifics. For instance, the very similarly-plumaged King and Emperor Penguins have UV-reflective spots in different positions on their beaks.

In general, beak color depends on a combination of the bird's hormonal state and diet. Colors are typically brightest as the breeding season approaches, and palest after breeding.