By ED KANZE
The question often comes up when I’m leading nature walks: Do birds live in birdhouses? The answer, generally, is no.
Birds build nests in birdhouses. Nests are for depositing eggs, sitting on eggs, and nurturing the gawky helpless hatchlings that emerge from them. When hatchlings grow up and flee the nest, the parents vacate the premises, too.
Birds such as American robins that often nest multiple times in a neighborhood in a season typically build a new nest each time. This probably makes good sense, at least mostly. Parasites move into birds’ nests and accumulate in them. Best to start off with a fresh nursery each time. Bluebirds often build multiple nests in the same box in the same year, but they may pay a price for it. Parasitic fly larvae hide under the nesting material by day. At night they rise, latch on to the tender legs and bottoms of the nestlings, and steal their blood.
Once my wife, Debbie, and I were standing on a bridge looking at an eastern kingbird nest. The cup of grasses, weed stems, and moss had recently disgorged the offspring raised in it, and Debbie asked a good question. Would the kingbirds come back the following year and reuse the nest? Expert naturalist that I am, I told her the birds would come back the next year if we were lucky, but they would surely build a new nest. You can guess what happened. The kingbirds came back and fixed up the nest and used it to rear another batch of insectivorous offspring. They used it a third year, too. But this is generally not the norm.
As we grow older, we realize that things that are generally true tend not to be true all of the time.
Among the birds we’re most familiar with, woodpeckers most often break the nests-are-just-for-nurturing rule. They are known to excavate cavities in trees to use for winter shelter. I first learned this while watching a downy woodpecker hollow out a bivouac for itself in the limb of an old oak. The time was October and early November — awfully late for nesting. Once the retreat was complete, every night just at sunset the woodpecker would appear, glance around furtively to make sure the coast was clear, and slip inside. Occasionally if I was up early, I caught the downy popping out for breakfast.
Our most frequently seen squirrels, the gray and the red, make two kinds of nests. They cut and rearrange branches to make big leafy stick nests called dreys. These are presumably drafty and used mainly in the warm months. Squirrels usually have multiple dreys and relocate from one to the next from time to time. The primary reason that seems to drive them to do this was brought home to me during the years I held a wildlife rehabilitator’s license and handled injured and orphaned squirrels. They were almost always covered with fleas. If you were to host your own personal flea infestation, you’d probably change sleeping quarters frequently, too.
Winter homes for squirrels are, as a general rule, better protected from the elements. Old woodpecker holes are often modified and pressed into service, as are birdhouses and attics and backyard sheds.
All of this begs the question: In winter, where do most of our birds sleep if they’re not holed up in nests and birdhouses? The answer is that they seek thick cover, often in evergreen trees and shrubs, where they are protected from wind and where the temperature may be a few life-saving degrees warmer than in the open. Some, such as crows, huddle in dense groups with their neighbors. Ruffed grouse often plunge into deep, fluffy snow if it’s available, snow being an excellent insulator. Wild things improvise. Necessity, as the wise old saying goes, is the mother of invention.
Ed Kanze is a Westchester-born author, naturalist and licensed guide who lives in the Adirondack Mountains. His latest book, “The Nature of the Place,” will be published in March, 2025.