Sparrow - Puffed Up to keep warm!

Photo by D. Carlson

Birds will “puff up” in the winter to keep warm. Air is an excellent insulator. That means that heat doesn’t pass well through it. When a bird puffs up its down feathers, it’s trapping air in-between them. This has the result of surrounding the bird’s body with a layer of air that acts as an insulating shield. This way the bird’s own body heat won’t escape as easily.