For the Birds Radio Program: Winter: Snow-bathing Snow
Winter affects birds in a lot more ways than you might think. Food is hard to find and drinking water is frozen up, and much of the day’s energy is spent seeking shelter from the wind and soaking up rays of the sun, all the while searching for food to stoke up the metabolic furnace. The long nights mean not only is there less time to find food, but also that more hours will be spent in vulnerable sleep, hoping an owl or fox won’t come near. If all that weren’t bad enough, cold weather also means that it’s impossible for a bird to take a bath.
Keeping feathers sanitary is essential. Not only are clean wing and tail feathers critical for flight, but also dirty feathers can’t insulate. And yet right when insulation becomes most crucial, when the temperature drops below freezing, it becomes impossible for songbirds to bathe in water.
Birds, like humans, have oily secretions from their skin which must be washed off or become unhygienic over time. Small particles of dirt on the feathers break attachments in the barbs and barbules, making flight more difficult. And feathers and skin mites multiply at horrendous rates unless their numbers are checked by bathing. But what’s a bird to do when there’s no water in liquid form to be found anywhere?
The crows in my neighborhood take snow baths. They drop down onto the snow n my next-door neighbors’ yard and thrust their heads and beaks into the crust, tossing snow on their backs and wings and rubbing their undersides in the white powder. Not only can the snow scrape off dirt and oil, it also has the advantage of being so cold that it probably immobilizes and scrapes off mites or freezes them long enough for the birds to pull them off—at normal body temperature, mites scurry for cover when a beak comes near, and most manage to stick with their reluctant hosts long enough to multiply. But despite its benefits, snow bathing has risks. If a crow falls through the crust onto powdery deep snow it will have one heck of a hard time getting out. And while it’s concentrating on bathing, a predator could sneak up for a nice, clean meal. There isn’t much that’s more conspicuous than a big black bird flopping around in a pile of snow. My crows wouldn’t dream of taking a snow bath in my own yard, with all the bustle of the bird feeders. They do their bathing next door, where they presumably feel safer.
Many birds probably go the entire winter without bathing at all. Their skin secretions amount to a lot less than those of humans, and they don’t have any sense of smell anyway, so they don’t seem to object to hanging out together even after months without a shower. Their feathers do get dirty, but even without water, they can clean feathers by preening.
Just about everyone has drawn a feather through his or her fingers at one time or another, noticing that openings in the barbs seem to zip closed if you do it just right. Birds combine this straightforward zipping action with nibbling on the feather to remove dirt, oil, and parasites, and with rubbing movements to spread preen oil throughout the feathers for waterproofing.
Preening appears to be very pleasurable for birds—they close their eyes as they scratch, stretch, and fluff their feathers out. As the days grow warmer and longer, birds won’t have to spend quite so much of their time searching for food, and they’ll be able to spend more time preening. They seem to prefer preening when the sun is shining, perhaps to maximize vitamin D production when the skin is exposed to sunlight. And as the rays of the sun grow strong enough to melt snow, birds will joyously take part in that annual rite–spring cleaning.
(Recording of a American Crow)
This is Laura Erickson, and this program has been “For the Birds.”