Now that the big snow has come and gone, colder temperatures will undoubtedly follow. It’s during times like these, when the thermometer plunges to well below zero in the dead of night when the forests and fields are covered in darkness, that I wonder; “How do birds survive?!”
That most species of birds claiming Minnesota as their temporary residence each year migrate to warmer climates should come as no surprise to anyone. After all, many people do the same thing. But for the hardy handful of feathered friends that remain behind to do battle with Mother Nature’s Old Man Winter, well, my hat is off to them.
At this writing a small assortment of year ‘round avian residents are gathered at the feeder for a breakfast of black-oil sunflower seeds and suet. The guest list includes any and all our wintertime resident birds, yet it generally is the same species that show up each day.
Blue jays; black-capped chickadees; downy, hairy, red-bellied, and pileated woodpeckers; and both white-breasted and red-breasted nuthatches are the standard assortment of visiting birds. Their daily comings and goings are dominated by their flying off with seeds and chunks of suet and fat clenched tightly in their beaks followed by unending caching activities—underneath bark, wedged in tiny holes on limbs and trunks, and wherever else these birds find for hiding spots.
Other birds that come and go but with less frequency are small bands of European starlings, erratic flocks of American goldfinches and pine siskins, a pair of pigeons, and, depending on the particular year, sometimes a dozen or so pine grosbeaks and large flocks of common red polls. Crows and ravens also show up from time to time to pick up residual seed and whatever foodstuffs they might find as they waddle on the snowpack searching the ground beneath the feeders.
It’s important that birds have access to high energy foods during the winter in order to maintain their metabolic needs. Those delicate looking feathers and under-feathers, including down, while seemingly fragile-looking structures that couldn’t possibly offer much protection against the bitter cold, do in fact provide the insulative qualities that birds need for survival. Some amount of body fat also helps keep birds warm, too.
We humans have a hard time understanding how it’s possible that a bird’s tiny feet and tiny legs, which are mostly completely bare and exposed to the elements, don’t freeze solid. Only a few birds, actually, have fully feathered legs and/or feet. Indeed, there’s a physiological answer to the problem—counter current heat exchange. Blood vessels in the legs and feet are arranged in such a manner that allows for cooler blood to be warmed by warmer blood from adjacent vessels.
Behavioral adaptations also help birds survive winter storms and frigid nights. In the most inclement weather, having access to shelter is critical. The downwind side of trees is a minimum shelter, but all kinds of other shelters and strategies are also employed by birds. Chickadees, for example, seek refuge inside both natural and artificial cavities, be they in trees or bird houses.
An example of a manmade structure is the roosting box that I have mounted on a support column of my house. The wood box has a tiny entrance hole at the bottom side, whereas inside the box are an arrangement of dowels that serve as perches for roosting chickadees. Chickadees routinely enter the roost box, and many other types of cavities, in small groups, thereby taking advantage of not only the shelter itself as a shield from cold and wind, but also to “huddle” together in order to share one another’s body heat.
Physiological strategies are also important to the survival of many birds. Metabolic rates decrease at night, allowing birds to enter states of torpor—a sort of mini-hibernation—that effectively eliminates the need to eat and expend high amounts of energy just to remain alive and to stay warm. Other birds such as ruffed grouse and sharp-tailed grouse will burrow into snow to spend cold nights and stormy days inside of individual “snow roosts”.
We human beings have it pretty good inside our warm homes and clothing. And though many of us find it nearly impossible to understand how delicate birds can survive winter’s onslaught, knowing that they do survive—and with apparent relish and delight—is assurance enough that all is well with our feathered friends as we get out and enjoy the great outdoors.
Blane likes to hear from his readers. Email him your favorite outdoors experiences and wildlife encounters at email@example.com.