Flamingos are pink or orange or white depending on what they eat. Flamingos eat algae and crustaceans that contain pigments called carotenoids. For the most part, these pigments are found in the brine shrimp and blue-green algae that the birds eat. Enzymes in the liver break down the carotenoids into the pink and orange pigment molecules that are absorbed by fats deposited in the feathers, bill, and legs of the flamingos.
Flamingos that eat mostly algae are more deeply colored than birds that eat the small animals that feed off of algae. So, you typically find deeply-colored pink and orange flamingos in the Caribbean, yet pale pink flamingos in drier habitats, like Lake Nakuru in Kenya.
Captive flamingos are fed a special diet that includes prawns (a pigmented crustacean) or additives such as beta-carotene or canthaxanthin; otherwise, they would be white or pale pink. Young flamingos have gray plumage that changes color according to their diet.
People eat foods containing carotenoids, too. The molecules act as antioxidants and are used to produce vitamin A. Examples of carotenoids humans eat include beta-carotene in carrots and lycopene in watermelon, but most people do not eat enough of these compounds to affect their skin color. People who take canthaxanthin pills for sunless tanning (artificial tans) experience skin color change. Unfortunately for them, the color is more of a bizarre orange than the natural tan from melanin!
- Hill, G. E.; Montgomerie, R.; Inouye, C. Y.; Dale, J. (June 1994). "Influence of Dietary Carotenoids on Plasma and Plumage Colour in the House Finch: Intra- and Intersexual Variation". Functional Ecology. British Ecological Society. 8 (3): 343-350. doi:10.2307/2389827