Why do flamingos stand on one leg?

In a large, shallow body of water, hundreds of flamingos congregate like an avian water ballet team: all preening their pink feathers, resting in the sun and standing on one leg for hours at a time. Flamingos even sleep that way.

Bird Image Gallery

It's a puzzle to science why, exactly, flamingos stand on one leg so regularly. But there are lots of theories on the subject. It's an impressive ability, considering flamingos' legs are longer than their bodies, and most of their weight is oriented horizontally. Humans are oriented vertically, with almost all of their weight in line with the center of gravity. It really should be easier for humans to stand on one leg than for flamingos. But most of us have trouble standing one leg for 10 seconds, let alone four hours like flamingos do.

Most large wading birds have the ability to stand on one leg, and flamingos are one of the biggest wading birds out there. They range from 32 to 51 inches tall (81 to 130 cm), but they don't weigh much -- just about 5 to 8 pounds (2 to 3.6 kg) [source: SeaWorld]. Combine their height with their coloring, and flamingos are one of the most recognizable birds in the world. They're practically a city logo in Miami.

It's startling to see a large group of pink, red or vermillion birds standing in a shallow pond. The color comes from the food they eat, including shrimp, which is full of carotenoid pigments (the same thing that makes carrots orange). Flamingos are always in groups, anywhere from a few birds to a few hundred or even thousands, and they live on every continent except Australia and Antarctica [source: San Diego Zoo]. They're very social, sleeping, preening their feathers and eating together. Imagine hundreds of birds with their heads under water, fishing. Or sort of fishing: Flamingos stick their heads in the water upside down and suck mud and water in through the front of their beak. The top and bottom of the beak have bristles that intertwine when they meet, forming a comblike filtering mechanism. The water and mud flow through, getting pumped out the sides of the beak. What's left is the flamingo's food, usually algae and small crustaceans.

They stand on both legs to eat, but on one leg to sleep. It seems like sleeping would require both legs on the ground for balance -- since the animal is unconscious. So why do flamingos do it? On the next page, we'll look into some of the most common theories.

Flamingos: A Leg to Stand On

If you stood in the water all day, what would happen to your skin? You'd look like a prune, most likely. Well, wading birds have the same problem. This is where one of the theories comes from: Maybe flamingos stand on one leg to dry their other foot off. Since flamingos alternate which foot they've got in the water, this theory does seem possible, but it's not terribly popular.

Some experts think the one-leg balancing act might have to do with a flamingo's brain. Many animals, including dolphins and ducks, only turn off one side of their brain at a time when they sleep. Ducks have also been known to stand on one leg for long periods of time (along with herons, storks and geese). If flamingos, too, keep half their brain awake while they sleep, that could explain why they sleep on one leg. The leg controlled by the side of the brain that's awake stays on the ground to maintain balance while the other leg and foot get to rest up for a while.

The most common theories, though, relate to hunting and energy conservation.

Since a flamingo's legs are so long and make up the majority of the bird's height, it takes a lot of energy to pump blood through both legs. That's a big strain on the heart. It's possible that pulling up one leg to rest, and tucking it up into the body, allows the heart to more easily pump blood through the body, since only one leg is fully extended. At the same time, it could conserve body heat. It's like wrapping your arms around your torso to stay warm in cold weather; the more compact you make your body, the easier it is to warm up. Since flamingos do sometimes live in cold weather, it's likely that standing on one leg has something to do with saving body heat. It's an imperfect theory, though, since flamingos stand on one leg in hot weather, too.

A flock of pink flamingos stand out against the blue waters of Lake Nakuru in Kenya.
Keren Su/Photodisc/Getty Images

Another common theory relates equally to both warm and cool climates. There are many scientists who think flamingos keep just one leg in the water in order to better camouflage themselves. A lagoon has lots of long, thin objects in it, including reeds and small trees. A flamingo on one leg could resemble a tree with a thin trunk leading to a much bigger top -- especially when seen from in the water, which is where a flamingo's prey lives. This theory would make more sense if the flamingo's prey were a bit more sight-driven, though. Shrimp, mollusks and algae don't seem to spend much time looking out for hungry birds.

So nobody is sure exactly why flamingos do it. But there's an interesting anatomical mechanism that may help explain how they do it. A flamingo's ankle is where you'd expect the knee to be -- near the middle of the leg. The knee is so far up on the leg, it's usually hidden by the body. That ankle has something a human ankle doesn't -- the joint actually snaps shut to literally lock the foot-to-leg junction in place. Some scientists think this locking mechanism might be the key to a flamingo's incredible balancing act [source: Necker].

For more information on flamingos, wacky animal behaviors, bird anatomy and related topics, flock to the links on the next page.

Why do flamingos stand on one leg?

Flamingos: A Leg to Stand On

Lots More Information

Related HowStuffWorks Articles

More Great Links