No birdwatcher’s life is complete without experiencing the penetrating gaze of a great gray owl. Even a glance from those lemon-yellow eyes will cut through your Carhartts. Designed for the cold, great gray owls are mostly feathers – a deep, downy layer covering a relatively small body. A great gray can locate its prey, often a small mammal, not by seeing but by hearing it move within deep snow. It will float on broad wings and then plunge, face and talons first, to snatch a vole or some other unlucky prey from beneath the snowpack. Great grays range from central Canada up into Alaska. And with that arsenal of adaptations, they need not migrate south in winter. Great gray owls scoff at winter.
Yet every so often, great grays do indeed move south and show up in the northeastern United States. It is a winter birdwatcher’s dream fulfilled. And it is but one example of winter birding at its finest.
Birds migrate to survive but not necessarily to escape the cold. Migration is often about food – or the lack of it. Those flycatchers arriving in May, for example, leave us when we run out of flies for them to catch. This type of exodus is inevitable and predictable for roughly three-quarters of our nesting birds. Yet while many birds leave us for the winter, some exciting replacements, mostly from the north, come to stay.
The lanky rough-legged hawk, which nests across the arctic, heads south and adopts our agricultural lands to hunt for meadow voles. The elegant American tree sparrow, which nests in scrubby areas of tundra, visits our shrubs and birdfeeders for seeds each winter. These are among the predictable winter visitors. They vacate their arctic breeding grounds entirely for the beckoning country farther south. But other species are more or less nomadic, moving south some winters and not in others. We call these “irruptive” species, and what often drives them south are episodes of food scarcity in their usual wintering grounds.
Great gray owls move south when their prey base of mammals crashes. Bohemian waxwings, which breed from Hudson Bay and across the taiga into Alaska, appear in huge numbers across New England some winters, presumably after exhausting fruit supplies in their northern wintering grounds. And that classic group of irruptive species, winter finches, including the pine grosbeak, descend upon us when their winter diets of buds, seeds, and fruits are in short supply. Sometimes food isn’t the only factor. A good breeding year, producing an abundance of birds and, therefore, greater competition for food in winter feeding areas, will force some of the excess population south.
Those grosbeaks, which breed and spend winters in subarctic and subalpine coniferous forests, and therefore rarely encounter people, like to feed on the fruits of our ornamental crabapples in cities and villages. They are normally tame and approachable – even more tame and approachable if, while imbibing on fermented fruits, they have had a “few too many.”
So do indeed keep those binoculars at hand this winter. You never can tell when you’ll happen upon a determined owl or a tipsy finch.
Bryan Pfeiffer is an author, wildlife photographer, field guide, and consulting naturalist who specializes in birds and insects. He lives on Bartlett Hill in Plainfield, Vermont.