Bird Watcher's General Store

Birds On One Leg
03/06/20


Dear Bird Folks,

Hereís a photo of a Red-shouldered Hawk that my friend sent to me. Notice that the hawk is standing on one leg. I was told that birds sometimes keep one leg tucked up in order to conserve heat. That makes sense when itís cold out, but Iíve seen them do it in warm weather as well. Any explanation?

Ė Diana, Huntsville, TX

Thanks, Diana,

Thank you so much for your very complimentary note. I didnít include your kind words along with your question because most of my readers wouldíve thought I was making it up, which I usually do, but not in this case. You are now my favorite Texan, next to Sandra Day OíConnor. Do you know her? I donít, but she sure has a nice last name.

More often than not, when folks see a bird on one leg they think there is actually something wrong with it. For example: When they see a ďone-legged gullĒ standing on a piling or in a parking lot, they immediately assume the bird must have lost its leg in a trap, or to a predator or in a circus accident. Or, the missing leg is a birth defect due to pesticides or from eating too much bad dumpster food. Why birds stand on one leg has been subject to much debate and the answers are varied and filled with speculation. In other words, just pick an answer you like and go with it. Thatís what I do.

Surprisingly, birds actually lose very little heat through their naked feet. Their legs have a countercurrent blood flow, which helps to minimize heat loss. Nevertheless, when itís really cold, birds will take extra measures to keep their extremities warm. Ducks, for instance, are well adapted for living in cold water. Even in the coldest part of winter, water wonít fall below 30 įF (or it would become ice). Things are different, however, when ducks move onto land. A few winters ago we had a really bad cold snap and many of our lakes and bays were frozen. Dabbling ducks (the ones that feed in the shallow areas) were forced to forage on land. As soon as they found an edible patch, theyíd pull one and sometimes both legs into their feathers and eat while resting on their bellies. The air temp was just too frigid and the ducks had to cover their exposed areas. This is an extreme example, but it proves birds will indeed retract their legs in order to save heat. But what about when itís not cold outside and birds still tuck in one of their legs? Have you thought about that, Diana? Wait! That was your question. I knew it sounded familiar.

If you look hard enough, youíll likely find an image of just about any bird standing on one leg. Owls, herons and sandpipers will all regularly strike the pose. But no bird is more noted for doing it than the flamingo. From photos to cartoons, the pink bird is habitually depicted on one leg. Yet, many flamingos thrive in tropical areas, where heat conservation isnít a big concern. If itís not trying to stay warm, what does a flamingo have to gain by tucking up one of its legs? One suggestion is that itís a ploy to fool the fish. The fish, in theory, think the birdís single leg is just a harmless stick in the water, so they donít avoid it. Thatís great, except flamingos donít eat fish. They are filter feeders, siphoning tiny shrimp, seeds and algae through their weird beaks, not fish. Another thought is the birds are just trying to keep dry, one leg at a time. Flamingos spend most of their lives standing in water, so why not let one leg totally dry off every once in a while? Others take a more scientific approach. They speculate that flamingos sleep like this because they have the ability to shut down half of their brain (like some people we know), while the other half remains alert. The awake half holds the bird up, while the sleeping half, with the tucked leg, snores away. Finally, thereís a school of thought that standing on one leg might help the birds save energy. Their heart has to work hard to pump blood through those long flamingo legs and back again. Tucking one leg saves the heart a bit of extra work. But does it really? Changing the position of the leg doesnít make it shorter. The blood still has to travel the same distance, right? Iíll have to dig out my old geometry books and get back to you.

I wonder if anyone has considered that the reason birds stand on a single leg is simply because it feels good. It turns out someone has. A recent study at Zoo Atlanta indicates that flamingos are basically more comfortable, and somehow more stable, on one leg. It all seems counterintuitive, but it may be true. When birds are active, they have both feet firmly planted, ready for action. But when theyíre chillaxing, they maintain a less stressful posture, like we do when we put our feet up after a long day. Being comfortable and stable on one leg is a hard concept for humans to understand, but who are we to judge? Standing on one leg looks shaky, but I know people who arenít steady even on two legsÖespecially on weekend nights.

Heat conservation is clearly a major reason why birds tuck a leg or two into their feathers, Diana. And, of course, there can be actual injuries. Other reasons appear to be more speculative. But I donít think we can discount comfort. The Red-shouldered Hawk in your photo might be standing that way just to relax. We all like to relax once in a while, especially Sandra Day OíConnor. She enjoyed relaxing so much that she even went to work while still wearing her robe. Hey, maybe I should try that; it looks super comfy.




Artwork by Catherine Clark


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