Have you ever come across some birds standing on only one leg? There is actually a curious but logical explanation for this! I was innately curious about this and did a little digging on the net for answers and here’s what I found:
Birds choose to stand on one leg mainly for three known reasons: (1) Reduction of heat loss to the environment, (2) Reduction of muscle fatigue, and (3) Good for resting behavior. By standing on one leg, the heat loss to the environment is reduced by half and in some birds such as flamingoes, the energy expended by retracted leg muscle activity is also reduced.
Now that we know that birds stand on one leg to reduce heat loss and to reduce muscle fatigue, let’s dive deeper into the details on how it works! Read on to find out more!
Standing On One Leg: Anatomy
Birds have many positions that they can undertake: standing, nesting, flying, and standing on one leg just to give a few examples. In order to understand why birds stand on one leg, we need to take a look at how it works first!
When a bird rests on one leg, the foot that is standing is actually positioned right below the center of gravity of the torso of the bird. This position requires the standing leg to be slanted at an angle to compensate for the shift in the bird’s weight. The center of gravity of the bird will be in line with the line foot of the bird. Information retrieved from http://www.reinhold-necker.de/seite11a.html
When birds stand on one leg, they do not actually experience the difficulty we humans face when we do the same. they are actually anatomically endowed with the right bone structures that allow for them to do so. In long-legged birds, their hips joint are able to sit and lodge in a bone structure known as the trochanter comb. This stabilizes the balance of the bird on the whole.
Why Do Birds Stand On One Leg: 3 Functions
So now we know that birds CAN stand on one leg only, there must be a reason why they do so. There must be some sort of benefit for them to do it, if not why would they do it at all? Now there are two functions as to why birds choose to take on this standing arrangement rather than stand on two legs. They are reduction of heat loss to the environment, reduction of muscle fatigue, and great resting behavior.
1) Reduction of heat loss to the environment
Firstly, let’s touch on the most highly studied reason as to why birds choose to stand on one leg: heat loss. You may or may not have noticed that bird feathers can keep their torsos and head warm, but what actually protects their skinny little legs from the heat loss to the environment?
The answer to the question lies in the importance of a bird’s legs in the role it plays as a site of heat exchange (Steen & Steen 1965). The bird’s leg arteries are actually right next to the veins in a bird’s leg! The colder blood in the veins is warmed up by the warmer blood in the arteries, helping the bird keep warm in cold environments.
Scientists have discovered that flamingos stand on one leg more often in the water than on the ground. In addition, they tend to stand on one leg during cool temperatures. These discoveries have led experts to conclude a thermoregulatory function of standing on one leg.
Also by standing on one leg, they are essentially tucking their non-feathered parts of their body (their leg) into their torso to reduce heat loss! This is to prevent unnecessary heat loss through the retracted leg especially when they are just sleeping or not moving around.
Therefore by standing on a single leg, there is a reduction of the heat loss to the environment by half! No wonder birds do it all the time!
2) Reduction of muscle fatigue
Secondly, we can consider how birds reduce their muscle fatigue by standing on one leg. We humans also often do the same actually! Do you find that you tend to stand on one leg or rest on one leg after you’ve been standing for long periods of time? I do too! Birds do the same!
In a study on flamingo cadavers, it has been shown that flamingos can indeed adopt a very stable support structure when they are standing on one leg. Their hip joint is stretched to the maximum to allow for it to stand on one leg. In fact, scientists have found that a simulated two-leg stance would require more energy to become mechanically stable than a single-legged stance.
3) Good for Resting Behavior
In another study, scientists have also discovered that the uni-pedal stance could be indeed a response to a certain type of half-awake sleep known as unihemispheric slow-wave sleep (USWS). USWS is a type of sleep in birds that help a bird maintain half their brain activity, to stay alert when they sleep. As such, birds adopt this single-legged posture as a result of achieving USWS in their sleep. By maintaining USWS, the bird would be able to stay alert to danger and predators, while ensuring that they do not fall into nearby water bodies. So by going on one leg, they are better able to maintain USWS, thereby increasing their awareness levels to respond to environmental cues.
Now that you finally know why birds stand on one leg, go out and never be confused again! Also, you now know a cool fact to share with your friends and family. Thanks for reading and happy birding!