Photo by Robert Hill
Photo by Robert Hill
Above : Red-winged black bird , female . Below : Carolina chickadee . Above : Red-winged black bird , male . Below : Red knots .
Photo by Robert Hill
Photo by Shauneen Hutchinson
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Pigments are responsible for many of the colors on a bird ’ s feathers , bill , legs , and bare skin . Two primary pigments influence the appearance of birds : melanin and carotenoids . Melanin is present in the plumage of almost every bird species and the skin of most birds . Melanin is responsible for producing both blacks and grays and earth tones such as rufous , chestnut , golden , and some yellowish hues . Dense deposits of melanin result in a deep black coloration like the red-winged blackbird ’ s plumage . Melanin deposited in lower concentrations results in lesser shades of black to gray . Just as highly concentrated melanin produces the black head and throat on Carolina chickadees , less concentrated melanin produces the gray in the same chickadee ’ s back . If no melanin is present , the feathers or tissue will be white . One category of melanin , phaeomelanin , often works in tandem with another class , eumelanin , to create every shade of brown from an adult bald eagle ’ s dark chocolate body to the rusty red head and breast of a red knot in May .
Carotenoids are the primary source of the bright reds , oranges , and yellows that we often see in brilliantly colored species . They are responsible for the pink plumage of the roseate spoonbill , the brilliant red of the male Northern cardinal , and the glowing orange body of a Baltimore oriole . Carotenoid pigments are generally only red or yellow in their pure form . Hue , or the shade of yellow , orange , or red , is determined by the mix of red and yellow carotenoids . Color intensity is determined by how densely packed the carotenoid pigments are deposited . For example , vivid reds result from the intense deposition of mostly red carotenoids . Lower concentrations of yellow carotenoids produce drab yellow results . Dense deposits of an equal mix of red and yellow carotenoids bring out the bright oranges .
Birds acquire pigments in two ways . They can create them from simple compounds available in their bodies or obtain them from food . Melanin is built from proteins called amino acids . Birds cannot make carotenoids ; therefore , they must eat a carotenoid-rich diet of fruits , seeds , plants , or animals . The carotenoids are processed in the liver and transported in the blood to a developing feather or tissue .
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