In winter, much of a singbirds' day is spent looking for food; they consume large quantities to supply the energy to keep warm at night when temperatures plummet. Fluffing their feathers creates an insulating layer of air. Their winter plumage can contain up to 30 percent more feathers than in summer. Many birds are able to slow their metabolism, lower their body temperatures or even reduce their heart rate to help them conserve energy. Some species gather in groups to search for food and to snuggle together at night to maintain body heat.

Winter birds will search for roosting places that provide protection from precipitation, wind and predators. They generally choose the same kinds of habitats that they use for nesting including cavities in trees, thickets, birdhouses, shrubs or evergreen trees. Even the smallest birds will thrive in the winter cold if they can find food.

The golden-crowned kinglet (Regulus satrapa) is only a little larger than a hummingbird. It can survive nighttime temperatures of 40 degrees below zero. The tiny birds roost in evergreen forests and huddle together in small flocks high up in the branches to help them stay warm. Wary of taking food from a birdfeeder, its winter diet is made up mainly of dormant insects and their eggs as well as overwintering caterpillars.