Layer upon layer of feathers are the world's best insulators! This Anna's hummingbird fluffed up her feathers for protection from the cold. All of this fluffiness is important. Fluffed-out feathers insulate a bird's internal organs so they stay at 104° F. Feathers themselves are such good insulators that the outside of the feather is cold, like the air, but just a few millimeters under the feathers, the bird's body temperature is a cozy 104°F. Snow doesn't melt on cold feathers, so the feathers stay dry.
Female Anna's John Doerper
