Flamingo

Flamingos are distinctive enough to be instantly recognized worldwide, yet almost everything about their biology is surprising. Their pink color is dietary. Their one-legged stance is thermodynamics. Their beak is upside down. And they're significantly older as a species than most people imagine — flamingo-like birds appear in the fossil record over 30 million years ago.

Facts you didn't know

• 1

  Flamingos are white without their diet. The pink color comes from carotenoid pigments in the algae and crustaceans they eat — captive flamingos fed a white diet become white. Zoos must supplement their food with carotenoids to maintain their color.

• 2

  A flamingo's beak is upside down relative to other birds. The upper mandible is the movable one (usually it's the lower), and the beak is held inverted in the water to filter food — the flamingo feeds with its head upside down.

• 3

  Flamingos stand on one leg to conserve heat — the single-leg posture reduces the amount of body surface exposed to cold water. A mechanical study found the posture also requires almost no active muscular effort, as the joints lock in place.

• 4

  Flamingo parents feed their chicks 'crop milk' — a red secretion produced in the crop that contains fat, protein, and, unusually, carotenoid pigments. The milk is red, and feeding it depletes the parents' color temporarily.

• 5

  Flamingos are highly social and won't breed in small groups — they require a minimum colony size (usually several hundred birds) to trigger breeding behavior. Zoos have used mirrors to convince small groups they're in a larger colony.