Coping with the weather
1 March 2005
Birds, like mammals, are ‘warm-blooded’. This means they generate their own body heat, instead of depending on the weather to warm them up – like reptiles do. So birds, like mammals, can survive in the coldest places on Earth. Emperor penguins can sit out the Antarctic winter at temperatures of -50ºC. Bar-headed geese can survive the same temperatures while flying at jet-plane height right over the top of the Himalayan mountains.
Special adaptations keep birds’ body heat inside. Feathers can fluff out to trap warm air, and are a useful place to tuck away your head when it gets cold. Fat that builds up under a bird’s skin as cold weather approaches also helps to keep it warm – just like thermal underwear.
Legs and feet
You might think that a bird’s bare legs and feet get very cold but a cunning adaptation of their circulation system prevents this. The arteries that carry warm blood from their heart pass right alongside the veins carrying cold blood from the legs, heating them up. In hot weather the flow of warm blood to the legs increases, so the bird can lose unwanted heat and keep cool.