Field Guide
From stashing food to roosting in groups, birds have the means to flourish.
How birds thrive in the cold
To withstand winter, birds take extra measures to stay warm and energized. Instead of reaching for mittens and long underwear like humans, birds grow more feathers, hide extra food and put on extra weight to fight the cold.
Cardinals, chickadees, woodpeckers and goldfinches all stick it out in colder regions while other birds fly to substantially warmer climates for winter. Some birds that stay in the northern U.S. breed in the far northern reaches of Canada in summer and fly only as far south as necessary to find food in winter. This means spending the winter in midwestern backyards, where their special adaptations help them keep warm and find food.
Juncos and American tree sparrows add extra weight for the coldest months of the year, gorging themselves when they can. The fat deposits they develop help them survive when seeds from plants and shrubs are covered with snow. Some species even change what they eat when their normal food sources are unavailable.
“Many birds like chickadees and nuthatches may be entirely insectivorous during the breeding season when there are lots of bugs around, but they switch diets in winter, becoming omnivores,” says Chris Whelan, an avian ecologist and professor of biology at the University of Illinois.
Chickadees survive by eating at backyard feeders and searching for hibernating bugs. Like tiny acrobats, they hang upside down probing all sorts of nooks and crannies in trees looking for overwintering spiders. Robins also change their diets in the winter. They survive by eating berries, instead of worms, which are hidden by blankets of snow.
Some birds, chickadees included, even grow their brains in late summer and autumn to improve their memory, according to the National Audubon Society. With extra brainpower, they are able to find the seeds that they cached in crevices in fall.
A growing brain is only one physical change these birds make. Many fliers the size of robins or smaller go into a type of “semitorpor” at night, Chris says: “They drop their body temperature and heart rate to conserve energy and heat.”
Goldfinches also sprout more feathers in winter than in warmer seasons. You will spot the birds puffing newly added plumage to trap warm air next to their bodies, giving them a fluffier appearance.
Many birds adjust their social patterns to survive the cold. While they might maintain their separate territories during the breeding season, in winter, golden-crowned kinglets huddle in small roosting groups in conifers to stay warm at night and during snowy spells.
Winter World author Bernd Heinrich says golden-crowned kinglets eat almost nonstop during the day in winter. They weigh about the equivalent of two pennies, but they spend their time constantly munching on overwintering caterpillars. Eating nonstop in winter? Too bad humans can’t do that.