A welcome sight in snow-laden trees and backyard feeders throughout the winter, how do birds that don’t migrate survive the below-freezing temperatures common in the north?
A steady diet. Food provides the energy songbirds need to stay warm, but they store very little as fat because the extra weight impedes their ability to fly. It’s important for these birds to have access to a steady diet of food each day, otherwise they may not have enough energy to stay warm overnight. Some birds, like the tufted titmouse (pictured) collect food for the winter beginning in fall.
Feathers. Fluffing up their inner downy feathers breaks the wind and provides insulation. Birds also produce oils to coat outer feathers, repelling water to stay dry.
Taking it easy. When it’s cold, birds cut down on energy-intensive behaviors such as nest-building, foraging across long distances, mating and even singing. Many small birds also enter a state of torpor overnight: lowering their resting body temperatures and metabolic rates significantly. This requires much less energy to sustain, but does make them more vulnerable to predators.
Escaping the wind. Whether huddling together in groups, using plants and other structures as shields, or roosting in tree cavities, birds have a variety of strategies for staying out of the wind.
Cold feet. While birds generally maintain high daytime body temperatures (around 105°F), their feet are kept at much lower temperatures by their circulatory systems. This prevents overall heat loss via a bird’s feet, which are more exposed than the rest of its body.