Why Are Flamingos Pink? Food, Pigments and Feather Make-Up

A flock of flamingos on a lake looks almost too pink to be real. Yet no flamingo is born that colour. The famous pink is borrowed, one mouthful at a time, from the tiny living things in the water. Flamingos are a living example of the saying “you are what you eat”.

Pink from the bottom of the food chain

The colour comes from a family of pigments called carotenoids. They are the same pigments that make carrots orange, tomatoes red and egg yolks yellow. Animals cannot make carotenoids themselves; they have to eat them.

In the salty, shallow lakes where flamingos feed, carotenoids are produced by algae and cyanobacteria. Small creatures such as brine shrimp eat the algae and store the pigments in their bodies, which is why brine shrimp are often reddish themselves.

A bill built like a sieve

Flamingos feed with their heads upside down. They sweep their bent bills through the water, and comb-like plates along the edges, called lamellae, trap shrimp, algae and seeds while the tongue pumps water out. A lesser flamingo can filter enormous amounts of water this way every day.

Once eaten, the carotenoids are absorbed in the gut and processed by enzymes in the liver. The modified pigments are carried in fats in the blood to the skin, to the growing feathers and to egg yolks. The more carotenoids a bird eats, the deeper its colour. Flamingos at some lakes are pale pink, others rich coral or crimson.

Born grey, pink later

Flamingo chicks hatch covered in grey or white down. For the first weeks both parents feed them a red, fat-rich fluid called crop milk, produced in the parents’ digestive tract and coloured by the same carotenoids. Making it can even make the parents paler for a while.

It takes young flamingos two to three years to reach full adult colour. Until then their grey feathers are gradually replaced by pink ones as the pigments build up.

Flamingos wear make-up

In 2010 Juan Amat and colleagues reported a surprising behaviour in greater flamingos. Birds rub their heads near a gland at the base of the tail, the uropygial or preen gland, and then spread the oily secretion over their neck and wing feathers. This oil is full of carotenoids.

The flamingos applied it more often during the breeding season, and the effect faded within days, so they had to keep re-applying it. The researchers described it as make-up: a way to look pinker than their diet alone would allow, because brighter birds tend to find mates sooner.

Why bother being pink?

Colour is a signal. A deep pink flamingo shows that it has found good feeding grounds and is healthy enough to collect lots of pigment. During group courtship displays, in which hundreds of birds march, head-flag and wing-salute together, the brightest birds are often the most successful.

In zoos the link is easy to see. In the past, captive flamingos fed ordinary diets slowly turned white. Today zoos add carotenoids such as canthaxanthin or beta-carotene to their food to keep them pink.

What about standing on one leg?

Flamingos often rest on a single leg, sometimes for hours. Several explanations have been suggested, and the question is not fully settled. In 2017 Young-Hui Chang and Lena Ting showed that a flamingo’s body is arranged so that it can balance on one leg with very little active muscle force, even when the bird is asleep. Standing on one leg may therefore be an energy-saving posture. It may also help reduce heat loss through the bare legs in cold water.

In short

• Flamingos are pink because of carotenoid pigments made by algae and cyanobacteria.
• They get them by eating brine shrimp and algae, filtered through their sieve-like bills.
• The liver processes the pigments and sends them to feathers, skin and egg yolks.
• Chicks hatch grey and turn pink over two to three years.
• Greater flamingos apply carotenoid-rich preen oil like make-up in the breeding season.
• Without carotenoids in their food, flamingos slowly fade.