杏吧原创

Why do some birds stand on one leg?

Thanks to all those who offered the answer: 鈥淚f they picked up the other leg they鈥檇 fall over.鈥� The old jokes are still the best 鈥� Ed

鈥� It has been proposed that the reason that flamingos stand on one leg is so ducks don鈥檛 swim into them as often! The most likely answer, though, has to do with energy conservation. In cold weather, birds can lose a lot of heat through their legs because the blood vessels there are close to the surface. To reduce this, many species have a counter-current system of intertwined blood vessels so that blood from the body warms the cooler blood returning from the feet. Keeping one leg tucked inside their feathers and close to the warm body is another strategy to reduce heat loss.

I imagine the converse is true in hot climates 鈥� blood in the legs will heat up quickly, so keeping one leg close to the body will reduce this effect and help the birds to maintain a stable body temperature.

Another factor in long-legged birds is that it may require significant work to pump blood back up the leg through narrow capillaries. Keeping the leg at a level closer to the heart may reduce this workload.

鈥淜eeping the raised leg at a level closer to the heart may reduce the work needed to pump blood鈥�

It is also worth remembering that birds鈥� legs are articulated differently to ours 鈥� what looks like the knee is in fact more like our ankle. Many birds have a mechanism to 鈥渓ock鈥� the leg straight, so for them it is much easier to stand for hours on end on just one leg 鈥� on numerous occasions I have seen birds take off, and even land, on one leg.

Rob Robinson, Senior population biologist, British Trust for Ornithology, Thetford, Norfolk, UK