Why are flamingos pink?

Source: Petr Kratochvil

Flamingos get their colors from the food they eat. Their diet consists mostly of the crustaceans and blue-green algae. Shrimps and algae contain organic pigments called carotenoids. The birds’ livers secrete enzymes which break down the carotenoids into pink and orange pigments, which are then deposited in the flamingos’ bodies and feathers.

Not all flamingos are pink. Some have very faint coloration and so appear white. The flamingos which eat mostly pigment-rich algae have more intense color than those which eat more shrimps. This is because eating algae directly delivers more pigment than eating shrimps – which themselves eat algae.
Flamingos in the zoos have pigments called canthaxanthin added to their food so that they look like visitors expect them to – pink. The same pigment is fed to farm-raised salmons so that they obtain desired color.