How do birds stand the cold when they don't fly south for the winter?
(Lansing State Journal, December 22,1993)
As you may have guessed, feathers play a primary role in staying warm enough. Even a small bird may have well over a thousand feathers. Muscles in the bird's body control the feathers, providing just the right amount of fluffing to keep the bird comfortably warm. Birds also will avoid particularly inclement weather. The thick cover of evergreen branches protects birds from the chilling wind. Some birds also will make dens in hollow tree trunks. Like people, they try to avoid going out if it is too cold.
Often, the key to surviving until spring is to find enough food during the sparse winter months. It takes energy to maintain a stable internal body temperature, and when it gets cold it takes more energy. That means that more time has to be spent searching for food. Foods such as suet and sunflower seeds provide extra energy by being readily digestible and rich in fats and oils. These foods also help to ensure that their feathers stay weatherproofed. Oils secreted from glands near their tail are spread over the feathers, and keep the bird's body dry event in a driving rain.