“Is there anything more beautiful than a beautiful, beautiful flamingo, flying across in front of a beautiful sunset? And he’s carrying a beautiful rose in his beak, and also he’s carrying a very beautiful painting with his feet. And also, you’re drunk.” -Jack Handy
The diversity of the world’s animals is one of the most fantastic natural marvels that life on Earth has delivered. From the sea to land to the air, there’s no shortage of wonders to explore. Today, though, I want to talk to you about one of the most bizarre sights of nature, as the 1989 supergroup Strength in Numbers once played about, the
These tropical birds are unusual — from a physical perspective — for a number of reasons:
- their long, skinny legs,
- their distinctive, pink color,
- and their long, flexible necks.
But from a behavioral point of view, flamingoes are perhaps best-known for their unusual stance.
Flamingos typically feed by standing with both feet in the water, muddying it to stir up seafloor creatures, and plunging their heads in to feed on algae, crustaceans, small fish, larvae and other tiny creatures. Shifting your feet to accomplish this requires both feet being in the water; flamingoes are not diving feeders like ducks are.
But when their beaks aren’t plunging under the water, you’ll almost never catch a flamingo with more than a single leg in the water unless it’s cleaning itself. In which case, all bets are off.
But what accounts for the properties of these avian curiosities?
Some of the traits of flamingos are pretty easily explained, biologically and behaviorally. They usually (but not always) have a pink or red color based on the carotenoid pigments in the crustaceans and algae they eat; a dearth of this pigment results in paler, whiter flamingos.
The long legs and long necks work in tandem, and it’s easy to see why evolution would favor these traits in flamingos: the longer their legs and necks are, the deeper the waters they can reliably feed in. (They are, perhaps surprisingly, excellent swimmers, but the muddy-the-water and dig-in-with-their-beaks is really the only way they feed.) If shallow-water food becomes scarce, it’s the long-legged-and-necked flamingos that will survive.
But what’s the deal with the standing on one leg? Flamingos spend a lot of their time in the water, and whenever they’re there and not actively feeding, you can find them standing on just one leg, something that they even sometimes do when they’re on dry land.
Why on Earth would it be advantageous for a flamingo to stand on one leg instead of two?
Because physics, that’s why!
And it’s physics that anyone who’s ever been in the pool on a hot summer’s day will understand all too well.
Humans, like all mammals and birds (including flamingos), are warm blooded, and tend to be hotter than their surrounding environment. If you place an object like a warm-blooded creature in water, however, they lose their body heat 25 times faster than they do in air, and you lose that heat proportional to the amount of surface area in contact with it.
For a human, if you put just one foot in water up to your ankle (about 4% of your body’s surface area), you’ll lose as much heat through that one foot as you will through the entire rest of your body, assuming it’s exposed to air of an equal temperature. (Although, over time, your blood vessels in the water will constrict, slowing that heat loss a little bit, with other consequences.)
So for a flamingo? That one leg that’s in the water is losing body heat quickly, and given the large surface area of its foot, it could even comprise the majority of a flamingo’s body heat loss.
A flamingo that never learned to stand on one leg, that spent most of its time in the water with both legs immersed, would lose somewhere around 40-70% more body heat than a flamingo that did learn this behavior.
That means it’s free to spend more time in the water, more time feeding, and enables it to have more chances for success at being a flamingo, just by standing on one leg. No wonder it’s a behavior that gets passed down from flamingo-to-flamingo across the generations!
Like many things in biology, this is a rather “sloppy” behavioral adaptation. It’s advantageous for the animal in question at some times but not others, but they don’t seem to be harmed by the one-legged land stance, either.
And that’s one of the rare things in biology that we can figure out just thanks to some very simple physics! Hope you have a great weekend, and get to enjoy some of the wonders of the natural world.
An earlier version of this post originally appeared on the old Starts With A Bang blog at Scienceblogs.