Why are flamingos pink?

Flamingos are not born pink. Chicks hatch grey or white and develop color over the first years of life from their diet, which consists largely of algae, diatoms, and small crustaceans such as brine shrimp. Those organisms contain carotenoids, the same family of pigments that make carrots orange and tomatoes red. Enzymes in the flamingo's liver break the carotenoids down into pigments that are deposited in the feathers, beak, and legs. The intensity of the color therefore reports directly on diet quality, and a flamingo deprived of carotenoids gradually fades to white, which occurred routinely in early zoos before the mechanism was understood and keepers began supplementing feed.

Color functions as a signal precisely because it is expensive to produce. Research has found that brighter individuals tend to be healthier and more successful in competing for the best feeding areas, and color intensity peaks around breeding. Flamingos also produce a crop milk to feed chicks that is rich in carotenoids, and parents visibly fade during the feeding period as they transfer pigment to their young, which is among the more striking parental investment signals in birds.

Two other features are frequently asked about together. The distinctive downturned bill is a filter feeder, used upside down with the tongue pumping water through comb-like structures called lamellae that strain out food, a mechanism functionally similar to baleen in whales and evolved independently. And the habit of standing on one leg is not fully settled, but research suggests it requires less muscular effort than standing on two because of a passive locking mechanism in the leg, and it likely also reduces heat loss in the cold water where they feed.