Icy cold weather is finally here, and it always makes me think about the birds. They seem to survive sub-zero temps, but how? These pictures have given me a clue. The sheer numbers of feathers and layers of feathers that nature lavishes on a single bird are amazing. And I have read that air is one of the best insulators. So all they have to do is fluff their feathers, and it’s like they are wearing amazing down jackets! Here are some sparrows showing how it’s done.