Body Color Expression in Birds

Birds display various body colors and patterns; some of them exhibit very beautiful colors and complex patterns. The main part in birds that shows body color is feathers. There are three known systems for the expression of plumage colors: (1) eumelanin and pheomelanin produced by integumental melanocytes, (2) accumulation of dietary pigments such as carotenoids, pterin, and psittacofulvins, from foods; and (3) structural colors as a result of fine structure of feathers and without special pigments. The pigment cell type in the trunk region of birds is the only melanocyte that produces melanin (eumelanin and pheomelanin), which is the same as in mammals. Since birds have additional two mechanisms (2 and 3) as noted above, they exhibit colorful body colors that are not shown in mammals. Based on the contents and ratio of eumelanin and pheomelanin, the feathers exhibit white, orange, yellow, brown, gray, or black colors. Other colors such as bright yellow, red, or glossy metallic colors of red, blue, green, or purple, are derived by the second and third mechanisms. The body and feather color patterns and color combinations are determined in the feather root, during the feather developmental process. Body colors and patterns in birds often exhibit differences in body parts, age, sex, and season. Although during evolution, birds lost the colorful erythrophore, xanthophore, and iridophores found in lower vertebrates, they obtain dietary pigments from foods and show structural color due to the fine structure of feathers. With these colorations, feathers in birds often show amazing complex patterns. The diversity of body colors and patterns in birds are very important for their survival strategy.