For the Birds Radio Program: Ice Storm
Winter is hard on birds, but seldom because of the weather. Occasionally birds do succumb to severe cold, but generally because they were unable to find food. Feathers provide wonderful insulation, and as long as birds are active, or at least shivering, their muscles and metabolic rate provide plenty of heat.
Many winter birds defend a non-breeding territory. They become so familiar with their little piece of land that they know the habits of local predators, where the best hiding places are, and where food is most likely to be. Their familiarity also makes them aware of unusual circumstances, so they detect new predators and new food sources fairly quickly. Far more birds die during autumn migration, as they pass through strange habitats and face situations they’ve never dealt with before.
Our northern birds can deal with snow and cold without much trouble. Deep snow makes it hard for juncos and sparrows to find food, but if they don’t have enough feeding areas available, they simply head south. As long as the snow stays cold and reasonably soft, Great Gray Owls can plunge through it to get the mice and voles beneath. And that same deep snow provides grouse and Snow Buntings with shelter from cold and predators. Winter finches take their food from the treetops, eating in trees that hang onto their seeds through winter, such as birch, pine, and spruce. Chickadees and woodpeckers eat a lot of insects—especially eggs and pupae that are hidden in the crevices of various plants. Our northern birds are adapted to our northern winters.
The one form of weather that is exceptionally hard on birds is an ice storm. In Minnesota, most ice storms happen during spring and fall, but as the general warming trend makes our winters more like those of Iowa and Illinois, our birds will more and more face the same conditions that more southern birds have to deal with. Drops of ice are often larger than raindrops, and so they pelt birds harder, so most birds must sit tight during the storm, unable to eat much. And despite hiding out, their feathers often get coated. So birds can more easily die of hypothermia when it’s sleeting than in a blizzard, despite warmer temperatures.
Sometimes ice is so thick that it actually seals up the cavities in trees. There are known cases of Barred Owls and chickadees suffocating, entombed in their holes. And the added weight of a thick coat of ice often breaks off branches and limbs. When birds were roosting inside holes, they come crashing down, too. But birds in these situations are usually hidden from our view, so most birds that die in ice storms are never even detected, except by their absence. After one severe March ice storm in Duluth, I lost about 90% of my backyard chickadees.
But birds do have some defenses against ice storms. Their bodies detect falling barometric pressure, so they usually pig out the day before a storm, boosting their energy to help them survive. And they don’t get bored easily, so can bide their time patiently when forced to sit tight. Most ice storms don’t last very long, so birds can get back to their activity as soon as the weather moves on. Meanwhile, if you have bird feeders, keeping them filled and accessible during bad weather will be very helpful. If charity begins at home, your very own backyard birds are a good place to start.