For the Birds Radio Program: How birds survive winter
How can anything naked as a jaybird survive the winter?
(Recording of a White-breasted Nuthatch)
How do birds survive the winter? The first and foremost problem they must solve is finding food. A bird’s body is like a well-insulated house—as long as it has fuel to burn, it stays warm in the worst of conditions. Birds don’t have an oil or gas furnace—instead they burn calories from food in their metabolic furnace. As long as a bird has enough to eat, it can easily survive the worst Northland winter.
Herons, Osprey, kingfishers, and other birds that are designed for catching fish in shallow water obviously can’t succeed when a thick layer of ice covers their only food source. Crows, which are both opportunists and generalized eaters, have figured out how to steal fish from the lines of ice fishermen, and also eat chunks of winter-killed fish that wash ashore as the ice melts in spring. But when crows can’t find fish, they eat seeds, fruits, decayed meat, and roadkills.
The fish-gathering techniques of most fish eaters are far more refined and rigid, and these species must go far enough south to find open water. Herons and kingfishers go to the southern United States and northern Mexico, but most Ospreys go all the way down to Central and South America. Bald Eagles catch fish in the same manner, and from the same bodies of water, as Osprey, but eagles are reluctant migrants. They often don’t leave the far north until they absolutely have to, and then they usually go only as far south as necessary to find open water. Many stick out the whole season in Wisconsin and Minnesota—at least one or two are even wintering in the Duluth harbor. Eagles have a couple of advantages over Osprey in winter. First of all, eagles have a more generalized diet. If the water freezes, eagles can always scavenge on road kills and even catch mice. Second, eagles are much heavier than Osprey—an adult female Bald Eagle weighs 10-14 pounds, whereas an adult female Osprey weighs a mere 3 or 4 pounds. The added weight of an eagle gives it a survival edge in severe weather. Not only can it live longer without food, but its larger size allows it to conserve heat more efficiently.
Birds that eat flying insects must leave for the winter or starve, but those that can also eat insect pupae and eggs hidden in the wood or bark of trees can dig out at least enough food for survival. Flickers, which depend on ants for much of their food supply, go south, along with Yellow-bellied Sapsuckers, which return when the sap starts running in early spring. But Downy, Hairy, and Pileated Woodpeckers survive quite handily on a frozen food diet. Nuthatches and chickadees also get protein from insects which they pick out of tree bark. These insect-eating birds are generally the ones attracted to suet feeders.
A few robins survive the Northland winter every year by fueling up on mountain ash berries and crab apples. Bohemian Waxwings and Pine Grosbeaks are also attracted by these fruits. Most ground-feeding seed eaters go far enough south to get away from a permanent snow cover over their fallen seeds, but at least a few Mourning Doves and juncoes stick it out in the Northland all season. If they manage to find a sheltered spot where they can find enough fuel in the form of seeds to last the season, they survive.
Our winters hardly teem with bird life, but the hardy birds that hunker down for the duration with us are treasures that make living in Northland far more pleasurable.
(Recording of a Downy Woodpecker)
This is Laura Erickson, and this program has been “For the Birds.”