If I were as smart as most birds, I’d be loafing in the tropics right now, perhaps on a beach enjoying a pina colada. Alas, I’m not. Like our lingering birds, I must find an alternative way to survive the Maine winter. How do birds do it?
Different birds have different strategies, including the obvious first choice.
Leave. Most species do migrate. Some go as far as the southern tip of Argentina. Some barely go south of the Maine border. But they go. However, migration is fraught with its own peril. Predators lurk along the route.
Collisions with skyscrapers and towers decimate nocturnal migrants and outdoor cats take many more in daylight. Adverse weather kills. Mortality is especially high among inexperienced first-year birds.
Wander. Insect-eaters must go where the insects are. In most cases, that’s far enough south that a cold spell won’t eradicate their food supply. Birds that can survive on a winter diet of fruit and seeds aren’t restricted to southern climates in winter. They just need to locate a good winter crop of forage, and they will typically wander around until they find it. Finches and waxwings are champions of this strategy.
Nestle. On a cold winter night, some of Maine’s smaller winter residents are known to huddle in tree cavities or the inner boughs of conifers. Pigeons soak up the morning sun together on rooftops and telephone wires. Ruffed grouse bury themselves in the snow, taking advantage of the same insulation value that makes an igloo survivable. Think about a raging snowstorm. Can you remember seeing many birds exposing themselves to the wind and weather? Even when exposed, many winter birds fluff their feathers, trapping a pocket of insulating air.
Sleep. Some birds conserve energy by slowing their metabolism. Their heartbeats slow, and their body temperatures drop. Hummingbirds do this for brief periods. Mourning doves do it for longer periods, even days, entering a resting state called “torpor.”
Hibernation is a deeper, extended torpor. Only one bird species is known to actually hibernate. The common poorwill of the desert southwest can go for weeks, and even months, sitting on the ground without stirring.
Swim. If you’ve ever cooked a duck, you know how much fat protects their internal organs. No matter how cold the day is, if the water isn’t frozen, it’s warmer than the surrounding air.
Diet. The spruce grouse has a varied diet in summer. In winter, its digestive tract changes, and it can sustain itself almost entirely on conifer needles. The yellow-rumped warbler is primarily an insectivore, but it thrives on bayberries along the Atlantic coast in winter. Robins and bluebirds can survive on fruit for long periods.
Cache. Many winter residents hide food in the fall. Chickadees, nuthatches, and blue jays all do it.
Glean. If sub-zero temperatures killed off all the insects in Maine, they’d go extinct. Many insects, beetles, and spiders have a natural antifreeze that prevents cell damage in cold weather. They spend the winter inert, hidden in bark crevices. Chickadees, nuthatches, titmice, kinglets and brown creepers are good at finding them. Woodpeckers also forage for larger beetles and grubs.
Supplement. Most Maine birds don’t need bird feeders, but they do appreciate them when available. Feeders probably reduce mortality in our overwintering bird populations. Feeders are particularly helpful when short-term events like blizzards make foraging for natural food difficult.
Grow. Bigger birds can survive colder weather. They have a smaller surface area in proportion to body mass, helping them to better retain heat. Common ravens can survive at the Arctic Circle, even in winter. The smaller American crow wouldn’t be caught dead up there. Or maybe it would be caught dead.
Multiply. Some birds just make a lot of babies. Golden-crowned kinglets are the tiniest birds that can endure a Maine winter. They are not only champion gleaners, they’re champion baby-makers, typically producing two large broods per summer. Many won’t survive the winter, but enough remain to carry on the species.
And lest we forget, Maine isn’t really all that far north. We’re only midway between the equator and the North Pole. The 45th parallel passes right through the northern tip of Old Town. We’re the heart of the temperate zone.
By Arctic standards, Maine is positively balmy, which is why so many Canadian birds spend their winter with us. Here’s the best part: if I sit on a Maine beach this time of year, I don’t even need ice cubes to keep my pina colada cold.