Have you ever thought about how birds stay warm in the winter? During our recent snow here in Davidson I watched birds coming to our feeders all day long. We had a lot more than we see on an average winter day. What were they doing? Why were they eating so much? And why do they puff up their feathers? All of this, and more, has to do with how they keep warm. Birds have a warmer body temperature than humans do and they need a lot of food to help maintain that. They also use strategies like huddling together in cavities or seeking shelter in bushes or up against your house.
If this is interesting to you then you might like to read this article from Audubon: