Why do birds puff up and shiver in cold weather?
Birds that looked puffed up are actually fluffing their feathers. This increases the “dead-air” space between the feathers and the skin which traps warmth and helps retain body heat, sometimes increasing it by as much as 30%. Birds actually grow more feathers in winter too, because the more feathers, the more fluffing up they can do! Birds shiver in winter to increase their body temperature as well, in a process known as thermogenosis. It’s an almost constant behavior and helps them produce heat up to five times their normal rate in order to maintain their naturally high body temperature. Because it burns lots of calories, they must flock to the feeders each day to replenish their small fat reserves, which can only last about 24 hours. Why don’t birds’ feet freeze in winter? All birds have the ability to reduce heat loss by restricting the flow of warm blood into their legs and feet. Because their legs are mostly scales, sinews, and bones, there’s very little to freeze. The arteries an
