It’s sleeting in the Upstate this afternoon and snow is forecast for evening, so I’ve filled my bird feeders to the brim. Feeding birds in winter, especially when the weather is frigid, is important because burning calories is the best way for birds to create body warmth. Providing high-calorie seed and suet is almost as good as supplying an electric blanket.
Birds have other tricks for keeping warm too. Their feathers have an oil coating that insulates and helps keep them dry. Old feathers are molted in autumn, so new, thicker, and more numerous feathers are produced just before the coldest time of year. And when the temperature drops, they fluff their feathers to add a layer of insulating air, just like a down jacket.
Evergreen conifers are the bird’s best plant friend in winter, sheltering them from predators, precipitation, and blistering winter winds, so they seek out these densely branched trees and shrubs. Some evergreens also provide food in the form of nuts, seeds, or berries. A few of our natives, such as junipers and cedars, make a cozy bed & breakfast for both resident and migrating birds.
The toothpick-like legs of birds are covered in tiny scales, similar to our fingernails, which keep them from becoming frost-bitten. The legs also have a unique circulatory system with arteries and veins lying side by side, so the blood returning to the body is heated by that being pumped to the bird’s feet. When you see a bird hunched over its legs, you know it’s really frigid.
Understandably, larger birds deal with cold better than smaller ones. In fact, the smallest can lose as much as ten percent of their body weight overnight in bitter weather. Birds can shiver like we do, using their flight muscles to stay warm. And some, like chickadees, can slow their metabolism to conserve energy in a state called nocturnal hypothermia. In this torpor, the heart rate is lowered and the body temperature drops 10 to 15 degrees, or even more.
Others, such as the Eastern Bluebird, will roost together in tree cavities or birdhouses to stay warm. One winter, I was surprised to see 16 bluebirds enter a single bird box to coop together in a snowstorm.
Currently, my garden is home to a suet feeder and three seed feeders, one each filled with niger seed, black oil sunflower seed, and safflower seed. The suet draws smaller woodpeckers, such as the Hairy and the Downy, plus the Carolina Wren. The niger seed is a favorite of the Goldfinch, the black oil sunflower seed draws the Red-Bellied Woodpecker and the Nuthatch, and the safflower seed is eagerly sought by the Northern Cardinal, Tufted Titmouse, and Carolina Chickadee.