Flamingos are born grey; their food turns them pink.
Chicks hatch with grey or white feathers. The pink and orange colours come from carotenoid pigments in the algae and small crustaceans that flamingos filter out of the water.
Why is this true?
The pigments are broken down in the liver and deposited in feathers, skin and beak. Zoo flamingos fed a diet without carotenoids gradually fade back to pale.
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More about animals
Animals are the easiest place to find facts that sound invented. Three hearts, blue blood, cube-shaped droppings, a punch fast enough to boil water for an instant — every one of these is ordinary biology to the animal doing it. The collection here leans on well-documented behaviour and anatomy rather than folklore, so each entry comes with a short explanation of why the trick actually works and a source you can read next.