Friday, April 18, 2008 - by Kyle Waggener, Chattanooga Nature Center
Colors in birds usually come from pigments. Pigments absorb certain colors and reflect others - the reflected colors are what we see. Pigments can be divided into several groups: melanins, carotenoids, porphyrins and psittacins. Some colors are caused by the “nanosturcture” of the feathers and produce an “optical illusion.”
The most common type of pigment is melanin. Most brown, black, gray and some yellow colors are produced by melanin. Melanin is very strong and is made up of chemicals found in the bird’s body. Some birds have black wingtips to prevent wear on their flight feathers.
Carotenoid pigments come from birds’ diets. These pigments reflect red, yellow or orange colors. Male Northern Cardinals’ bright red color comes from eating different seeds and berries (mostly from Flowering Dogwood berries). The carotenoids are stored in the cardinal’s liver and then moves into their bloodstream during their molting process and are deposited in their new feathers as they start to grow. So a bad season of Dogwood berries might mike a male Cardinal less attractive to the ladies next year.
Porphyrins are very rare and are only found in a few groups of birds. This group of pigments gives African birds called turacos their green and red colors. Porphyrins also give owls and nightjars (Whip-poor-wills and Nighthawks) their reddish-brown feathers.
Psittacins are only found in parrots and produce their bright red, yellow and orange colors.
There are no blue pigments in any birds in the world. So why do Eastern bluebirds and Indigo Buntings look so brilliant? The answer is the sub-microscopic structure of the bird’s feathers. There is a central layer of cells with melanin in them surrounded by a “cloudy” layer that scatters the light waves in such a way that they interact with each other in a process called “constructive interference” causing the light to look blue when it reaches our eyes. If you were to look an Indigo Bunting in the shade it looks gray compared to when it’s out in full sunlight. White, most green colors and the throat patch or “gorget” found on hummingbirds also comes from feather structure.
Be on the lookout for many brilliantly colored birds that can be found at the Nature Center especially during the spring migration and mating season.