We’ve had a lot of snow this winter. Perhaps I’m not the first to point this out. Reader Paul MacLean asks: When weather gets extreme, what do birds do? Food and shelter are the immediate concerns.
Many of Maine’s wintering birds are wanderers. They go wherever the food is. If snow covers their food here, they’ll keep flying south until they find uncovered food. These include birds that typically forage in winter grasslands, such as snow buntings. Even American goldfinches may be forced southward, to be replaced by hardier finches, such as common redpolls and pine siskins.
Seed-eating birds have it easy. No matter how deep the snow, small finches can find catkins in the treetops of birches, aspens and willows. Larger finches, such as crossbills, subsist on cones. A good snowstorm only serves to show how well wintering finches forage. During some of the recent storms, my feeders were mobbed by flocks of redpolls and smaller numbers of siskins and goldfinches. But the day after the storm — nothing. There is so much natural food in the woods that they don’t need to risk attracting predator attention at a feeder.
Fruit-eating birds have it easier. Mother Nature provides native berries, such as mountain ash. Humans provide the rest — a smorgasbord of crab apples and ornamental berries. Typically, such birds ignore fruit on the ground, and thus deep snow is no impediment to a full belly. Cedar and Bohemian waxwings swarm berry bushes. American robins switch to a berry diet in winter and constantly surprise Mainers who thought they had all gone south.
Furthermore, much of the fruit is too firm to eat at the beginning of winter but softens as the freeze-thaw cycle turns it to mush. Berries soften at different rates, so there is a continual supply of food becoming available through the cold months. The only real question is whether the fruit-eating birds need to come to Maine at all. When there is enough food up north, they don’t bother. Or they come down late after exhausting the food supply in Canada. Or they come down early if the annual fruit crop north of the border is meager. Every year is different. Last year, the pine grosbeaks arrived very early and were gone by Christmas. This year, they waited until near the end of January to arrive.
The moral of the story is that bad weather is not necessarily bad for birds. For most of them, there is plenty of forage. If not, they leave.
I do worry about owls, though. I see and hear barred owls around my house year-round, but it is rare to see one in daylight. However, with over two feet of snow in my yard, one owl has taken to perching above my feeders. He arrived at noon one day and stayed three days. I’m certain he’s waiting for squirrels. Owls have such acute hearing that they can locate mice under the snow. But not 2 feet of snow. After a big storm, or in abysmal weather, mice and voles are not likely to emerge from beneath the snowpack for days. A barred owl in daylight means the bird is unusually stressed and hungry. I keep my distance.
It is a bigger challenge to stay warm in frigid weather, but every bird has a strategy. The first line of defense is downy feathers. Down is one of the best insulators in the world. When roosting, birds fluff up to trap more air in their feathers.
Birds know enough to stay out of the wind. One 40-year-old study documented feeding behavior in cold, windy conditions. On raw days, birds foraged closer to the ground and on the leeward side of tree trunks. Many birds roost in thick foliage, especially evergreens and backyard hedges. Chickadees, nuthatches and kinglets will huddle in woodpecker cavities, sometimes together to conserve heat. They shiver to warm up. Many small birds can lower their body temperatures, slowing their metabolisms to conserve energy. Ruffed grouse bury themselves in the snow to stay out of the elements. Foxes know this, so it can be a dangerous strategy.
Bigger birds have more body mass in relation to surface area, allowing them to retain heat. But the golden-crowned kinglet is the tiniest winter resident in Maine. They compensate by eating a lot, huddling together and using cavities to roost. Yet mortality rates are high. They sustain the population by using a time-honored technique: they make a lot of babies.
Bob Duchesne serves as a Maine Audubon trustee and vice president of its Penobscot Valley Chapter. Bob developed the Maine Birding Trail, with information at mainebirdingtrail.com. Bob can be reached at duchesne@midmaine.com.