How do birds keep warm in the winter?
Birds are warm blooded. In general, this means that they maintain their body temperature within a certain range even when the temperature around them changes. The maintenance of body temperature within a normal range depends on the amount of heat the bird produces and the way it conserves heat. In nocturnal birds, such as owls and nighthawks, the body temperature is higher at night when these birds are most active. On cold, wintry days, most birds fluff up their feathers, creating air pockets that help keep the birds warm. The more air spaces, the better the insulation. Some birds perch on one leg, drawing the other leg to the breast for warmth. Shivering is used by almost all birds for short term adjustment to the cold. It is the main way birds increase their heat production while the bird is at rest. Shivering converts muscular energy into heat for the short term and that energy must be replaced soon. To keep up their high metabolic rate, most backyard birds eat rich, high energy foo
