Most wild animals we see in the wintertime are warm-blooded, like us. Their bodies generate heat all of the time, which is a good thing, especially in the winter. Some mammals you might see in wintertime are squirrels, raccoons, deer and people. Other mammals, such as bears, hibernate in the winter, when they go into a deep, sleep-like state and they may not be seen until early spring. Their breathing, heart rate and temperature go down so they do not need to eat or drink. This happens in a well-protected place like a cave or burrow.
Birds are also warm-blooded and usually a lot more visible than most other animals in the wintertime. They often are seen looking for food to keep themselves warm. With enough to eat, their bodies can get up to 107 degrees, almost 10 degrees warmer than we are.
Let's compare how we keep warm to what birds do in cold weather. We wear warmer clothes, the same way birds can fluff out their feathers to provide more insulation. We make sure we protect our exposed skin by wearing something on our feet, hands and head. Birds pull their feet and legs up into their feathers to keep them warm, and sometimes tuck their beak under a wing for protection. We try to stay in a nice warm place unless we have to go outside, the same way birds find a protected place to hide at night when they are not out gathering food.
But some birds have a different way to keep warm during the winter -- they migrate south where it is warm. Some people will also move south for warm weather during the winter. They are commonly called "snowbirds."