Flamingos aren’t pink by birth or by genes alone. Their color comes from what they eat, and shrimp are only part of the story, because microscopic algae in the same salty lakes carry the same pigments.1IntechOpen. Haloarchaea May Contribute to the Colour of Avian Plumage in Marine Ecosystems The color also has to be kept up, so a flamingo’s shade says something about both its diet and its health.
Shrimp, Algae and the Pigment Behind the Pink
The coloring substances are carotenoids, the same family of red-orange pigments that colors carrots, tomatoes and cooked shrimp. Animals can’t make carotenoids from scratch, so a flamingo has to eat them.
In the wild, the pigments mainly come from microscopic algae called Dunaliella and from tiny crustaceans called brine shrimp (Artemia).2IntechOpen. Haloarchaea May Contribute to the Colour of Avian Plumage in Marine Ecosystems Both live in the very salty lakes and lagoons where flamingos feed.3IntechOpen. Haloarchaea May Contribute to the Colour of Avian Plumage in Marine Ecosystems Brine shrimp get their own color by eating the algae, so the pigment passes up the food chain. That makes “it’s because of shrimp” half true: the algae are the original source. A flamingo that eats algae directly takes in the pigment one step earlier.
The pigment doesn’t sit in the stomach like a dye. After a flamingo swallows its food, digestion releases the red-orange pigments and they are absorbed through the gut wall into the blood, much as fats are. The liver processes them, and some are chemically altered along the way, which is part of why the pigments in a feather aren’t always the same as those in the food. The blood then carries them to the skin and to growing feathers, where they are deposited.
The feeding itself is a steady, small-scale affair. Flamingos wade through shallow, very salty water and strain out food all day, so pigment arrives in small amounts, continuously, rather than in a few big meals.
Why Some Flamingos Are Redder Than Others
Flamingos feed upside down, straining water and mud through comb-like plates in their bills. The size of the gaps decides what gets caught: shrimp-sized food or tiny algae.
That is why species differ in their diets. The greater flamingo filters insect larvae, seeds, small crustaceans and similar food from mud, while the lesser flamingo has a much finer filter for blue-green algae and diatoms.4Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. The filter-feeding and food of flamingoes (Phoenicopteri) The two can share one lake without competing for food.5Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. The filter-feeding and food of flamingoes (Phoenicopteri) South American species also have filters with different gap sizes, which suggests each picks out different-sized food.6The Condor. Bill Morphology of South American Flamingos
Shades vary too. The American flamingo is brilliantly colored, while its Chilean relative is paler.7Comparative Biochemistry and Physiology. Metabolic fractionation, storage and display of carotenoid pigments by flamingoes Different species carry somewhat different mixes of red-orange pigments in their feathers.8Comparative Biochemistry and Physiology. Carotenoids of the roseate spoonbill
From Food to Feathers
Once absorbed, the pigments end up firmly anchored to the protein feathers are made of.9Comparative Biochemistry and Physiology. Carotenoids of the roseate spoonbill So color is locked in when a feather grows, not painted on afterward. Red pigment is laid into the bare skin of the legs as well.10Comparative Biochemistry and Physiology. Metabolic fractionation, storage and display of carotenoid pigments by flamingoes Old feathers bleach and are replaced at moult. New feathers only come in pink if the diet supplied pigment at that time, so a bird’s shade reflects its recent diet, not a lifetime one.
Flamingos also apply a kind of makeup. Greater flamingos rub pigmented oil from a gland near the tail onto their feathers, making them redder.11PubMed Central. The color of greater flamingo feathers fades when no cosmetics are applied It boosts color most in the breeding season.
The upkeep is needed because carotenoids bleach in sunlight, and flamingos live in open, sunny places.12PubMed Central. The color of greater flamingo feathers fades when no cosmetics are applied Without regular reapplication of the oil, this extra color fades.13PubMed Central. The color of greater flamingo feathers fades when no cosmetics are applied
Are Flamingos Born Pink
Chicks hatch with grey or white down. As a young bird grows, red pigments are deposited in new feathers and in leg skin, gradually replacing the darker grey pigment there.14Comparative Biochemistry and Physiology. Metabolic fractionation, storage and display of carotenoid pigments by flamingoes It typically takes two to three years to reach full adult color.
Both parents feed chicks a milk-like fluid from their throat, and it is bright red with pigment. Parents can look paler while feeding because their pigment is going to the chick.
Why Zoo Flamingos Stay Pink
Captive American and Chilean flamingos gradually lose the red of their skin and, through moulting, of their feathers unless they are fed carotenoid-rich food.15Comparative Biochemistry and Physiology. Metabolic fractionation, storage and display of carotenoid pigments by flamingoes So zoos add pigment to flamingo feed. Pellets contain added carotenoids, and sometimes shrimp or carrot-based supplements are given. Other pink wading birds, such as roseate spoonbills, store the same pigments when fed them.16Comparative Biochemistry and Physiology. Carotenoids of the roseate spoonbill
What a Flamingo’s Pink Tells Other Flamingos
Gut parasites block carotenoid absorption in poultry and reduce pigment-based color in several birds.17The American Naturalist. Is There an Immunological Cost to Carotenoid-Based Ornamental Coloration? So color likely depends on both food supply and parasite load.18The American Naturalist. Is There an Immunological Cost to Carotenoid-Based Ornamental Coloration? A pinker bird is advertising that it eats well and stays healthy. Pale birds aren’t necessarily sick, but color hints at condition.
Color shapes social life too. In greater flamingos, redder males were more likely to have a main social partner, and partners tended to be similarly colored.19PubMed. Plumage variation and social partner choice in the greater flamingo (Phoenicopterus roseus) Pinker flamingos also start more fights and dominate feeding spots.20Animals. Pinker flamingos are more aggressive, intriguing study finds By controlling food, bright birds may help keep their color and attract equally pink mates.21Animals. Pinker flamingos are more aggressive, intriguing study finds Their tinted-oil makeup acts as a signal booster for plumage color.22PubMed Central. The color of greater flamingo feathers fades when no cosmetics are applied