Black and brown colors on feathers come from melanin, the same pigment that’s in human skin. These colors are especially prevalent on birds’ flight feathers—for good reason. Melanin is very strong, and allows the hardest-working feathers to better resist wear and tear.
Warm colors come straight out of the food birds eat. Carotenoids create most of the reds, oranges, and yellows in birds. There are more than 600 types of carotenoids, and they all require photosynthesis to make, so birds have to borrow them from plants and a few types of bacteria and fungi.
Porphyrins create bright reds and greens and can only be found in a scant handful of birds.
Cool colors and iridescence come from crazy micro-structures in feathers. Keratin is a crucial protein in bird feathers. The way it’s structured allows light to twist and turn and separate into a rainbow of iridescence.
photo: Macroscopic Solutions/Flickr CC (CC BY-NC 2.0)