There have been a couple of questions recently about how color is controlled in bird feathers, so I thought I would explain that with some examples from some of my bird photos. One excellent explanation of coloration in bird feathers can be found at the Cornell Lab of Ornithology’s website: http://www.birds.cornell.edu/allaboutbirds/studying/feathers/color/document_view
To summarize their information, the color of bird feathers is formed in three ways: by pigmentation of the feather, by structural properties of the feather, or a combination of both. This post is about just the pigment part of color production.
There are three basic contributors to feather pigmentation: melanin, carotenoids, and porphyrins.
Melanin pigments give feathers a yellow-brown to black appearance, the density of color depending on the amount of melanin present. The presence of the melanin or any pigment actually strengthens the feather, and so we often see birds with white wings and black wing tips (e.g., gulls, terns, and white pelicans). However, melanin also makes the feather more susceptible to bacterial degradation, leading to frayed wing tips which are not good for the long distance flyers or aerial maneuvers.
White Pelican from Lac Qui Parle dam, Minnesota.
Carotenoids may be derived from plant compounds like the xanthophylls we see in yellow, orange, or red leaves in the fall or carotene we see in carrots. They must be eaten by the birds as the feathers are growing in during a molt, and some are modified by the bird to produce a specific color. Examples are the yellow of Goldfinches or the yellow and orange colors in some tropical tanagers and spring warblers.
Flame-colored Tanager in Boquete, Panama
Porphyrins are metalo-proteins synthesized from amino acids, like the heme protein in the hemoglobin of our red blood cells. These pigments produce pink to red colors, and in combination with melanin pigments produce the rich reds, brown, and greens of some tropical bird species, as well as owls, pheasants, turkeys, and other fowl.
Male Quetzal in Bouquete, Panama.
What pigments produced the color in this Keel-billed Toucan?