Flamingos Aren't Born Pink

Feed the Reader

1 day ago

5 min read

Picture a flamingo and you picture pink. Not just a bit pink. Lawn-ornament pink, the most committed pink in the animal kingdom.

So it can come as a surprise to see a flamingo chick. It's a small, fluffy, grey-white thing, with a straight little beak. No pink at all.

That isn't a phase the chick grows out of, exactly. The pink isn't waiting inside it, ready to come through. A flamingo has to eat its way to pink. And if it stops eating the right things, the pink fades away.

Pigments from the bottom of the lake

The colour comes from a family of natural pigments called carotenoids. They're the red, orange and yellow pigments made by plants and algae, and they're the same ones that colour carrots and tomatoes.

Flamingos are filter feeders. They wade through shallow water and sieve out their food: algae, small seeds, fly larvae, and tiny crustaceans such as brine shrimp. The algae are packed with carotenoids. The shrimp eat the algae, and take on their pigments too. So a flamingo gets a double dose: carotenoids straight from the algae, and more from the shrimp that ate them.

From stomach to feather

Eating the pigment is only the first step. A flamingo also has to process it.

The bird's digestive system breaks the carotenoids down, and the liver turns them into pigment molecules the body can use. These are carried in fats and laid down in the parts of the bird that are still growing: new feathers, and the skin of the bill and legs.

That last part matters. Feathers don't keep growing, so a flamingo's colour gets built up slowly, as the bird moults and grows new feathers to replace the old ones.

That's why chicks take so long to change. They start with grey-white down, and even their first proper feathers are pale. Pink creeps in moult by moult, and according to zoo keepers it takes a good couple of years, often two or three, for a young flamingo to reach its full adult colour.

Why zoos colour the food

Here's where it gets counterintuitive. If a flamingo's pink comes from its diet, then a flamingo on the wrong diet loses its pink.

Zoos can't easily give captive flamingos a lake full of algae and brine shrimp. So instead, many feed them specially made pellets with a carotenoid added during manufacturing. Often it's one called canthaxanthin. It's listed right there on the ingredients of one widely sold flamingo diet, which says it's added "to maintain the birds' vibrant plumage color". Zoos including ZSL London Zoo and Whipsnade, and Odense Zoo in Denmark, say they add it for exactly that reason.

How much does it matter? In 1992, when a European rule threatened to ban canthaxanthin in flamingo feed, Newsweek reported that it could "turn the birds gray". Without it, as old feathers drop out, new ones would grow in pale.

You might wonder whether this means you could feed a flamingo any colour you like. Sadly not. A zoo diet manager has explained that dyes which aren't carotenoids don't end up in the feathers. The bird simply breaks them down and gets rid of them. No blue flamingos, then.

Shades of pink

Not all flamingos are the same pink, and diet is a big reason why.

There are six species of flamingo, spread across wetlands in the Americas, Europe, Asia and Africa, and their colour varies from pale pink to much deeper shades. Partly that's down to what's available to eat in each place. Partly it's down to the birds themselves: research has found that the six species differ in their blood chemistry and seek out different carotenoids, which helps explain the range of hues.

Colour may also carry a message. According to BBC Wildlife, the brightest birds may rank highest, since keeping up a strong colour could mean being good at finding food. Some researchers think that may make colour a signal to potential mates.

There's even evidence that some flamingos touch up their colour. A study of greater flamingos in Spain found that the birds take carotenoid-rich oil from a gland near the base of the tail and rub it onto their neck, breast and back feathers, a bit like applying make-up. They did it most during the season of group courtship displays. The researchers suggested it may be related to mate choice, although, as with many ideas about animal signals, that's a suggestion rather than a settled fact.

Parenthood fades you out

There's one more twist, and it's rather touching.

Flamingo parents feed their chicks a liquid called crop milk, made in part of the throat and brought up through the mouth. Both parents can make it. It's rich in fat, and it's also full of carotenoids, so rich that it's bright red.

Those pigments have to come from somewhere, and they come from the parents. As the breeding season goes on, the adults pour so much colour into their chicks that their own feathers fade. By the end of the season, many parents look washed-out, almost white.

The chicks, meanwhile, are slowly getting their first taste of pink.

What diet doesn't explain

It's worth being careful not to make this sound simpler than it is. Diet supplies the pigment, but it isn't the whole story.

The bird's own biology decides how well it absorbs and processes carotenoids, which differs between species. Moult sets the pace, because pigment from the diet goes into new feathers as they grow. Breeding drains colour away. And outside the courtship season, the extra colour some birds apply fades too. A flamingo's colour is a running balance between what comes in and what gets used up.

A colour on loan

So a flamingo isn't simply born pink, and it doesn't stay pink by default. Its colour is borrowed from the algae at the bottom of the food chain, carried up through the shrimp, processed in the liver and laid down, feather by feather, over months and years.

In a sense, every flamingo is wearing a record of what it has eaten. Feed it well, and the record is bright. Stop, and it slowly fades back towards that grey little chick.