Homey was talking about the birds his family was enjoying, and the various types of food they were going through. “The kids really love this stuff, you know, and they like trying to identify the birds we’re feeding. With these really cold nights, my youngest girl keeps asking how the little birds stay warm. I tell them the food keeps their bodies warm – like fuel for little engines – but I know there’s more to their coping mechanisms, and I want to sound like I know what I’m talking about (I am the dad, after all)… So, what else keeps them from waking up frozen to death?”
“Well, you are right about the food, of course,” I said. “They have to eat regularly or they die, and, since different birds have different needs, we generally give them a choice of seeds and suet. Most of the foods we offer are fatty or oily since the oil is a good burning fuel to help keep their metabolic rates up. Let me dig around for this coping with the cold stuff, and see what all I can find for your conversation.”
Back in my office, I reached for “The Birder’s Handbook,” by Ehrlich, Dobkin and Wheye. Then I got on the horn to Deborah Essman (Bird Whisperer of Paradise and Official Birder of the Reecer Creek Rod, Gun, Working Dog & Outdoor Think Tank Benevolent Association) for her thoughts and observations on our common and occasional small birds of winter. Among the birds you may be feeding or seeing are the house sparrow, house finch, American goldfinch, black-capped chickadees, dark-eyed juncos, redpolls, pine siskins, red breasted nuthatch, and perhaps a couple downy or hairy woodpeckers. Some of these – and others not named – are irruptive, meaning that numbers of them may show up from time to time in response to (most commonly) food scarcity in “normal” wintering areas. Keep your bird ID book handy.
Metabolism is the conversion of food to the energy needed for life itself: for cellular activity; for the building blocks for proteins, carbs and so on; and the elimination of nitrogenous wastes – it is the sum of all chemical reactions occurring in living organisms. If metabolism fails the critter dies, so food is critical.
Different birds have different metabolic rates. Smaller birds have proportionately greater surface areas in relation to their body mass than do larger birds, so little birds lose their body heat faster in the cold. Since they all maintain similar body temperatures, small birds have higher rates of metabolism than big ones and eat proportionately more food. For example, hummingbirds have the highest rate of metabolism of any bird – maybe a dozen times that of a pigeon – and they must consume their weight in nectar daily. (It is said that a warm-blooded mammal could not survive if it was smaller than a hummer, since it could not eat enough to stay alive, but the tiny Etruscan shrew weighs less than a dime and somehow eats its body weight twice a day.)
Each bird has its own needs and many have special adaptations. The redpolls, for example, have a partially bi-lobed pocket about midway down their necks, where they can store seeds. The little chickadees are often seen “caching” seeds in some hiding spot. Most birds, however, just need handy food.
Once food is settled, other cold weather survival tools kick in. Feathers hold heat generated from metabolizing that food. We have all observed birds sitting “fluffed up” in some protected spot. This erection of feathers traps air in tiny pockets, providing excellent insulation (think down coats or featherbeds) – a bird’s skin temperature may be 75 or more degrees warmer than the air less than an inch away. You have likely noticed that juncos, finches and sparrows foraging in cold weather frequently drop down, covering their legs and feet with their breast feathers while pausing in their food search, thus minimizing heat loss from featherless parts of their bodies.
Dark objects commonly absorb more sunlight than lighter objects, and it has been assumed that dark-feathered birds absorb more energy that light-colored birds. Turns out that there are other factors at work; a great deal depends on such things as wind speed and whether feathers are sleeked (laid back) or erected. In fact, research indicates that erect white plumage gains heat, and resists heat loss better, than dark plumage in cold temperatures and moderate winds.
To help birds keep feathers clean – thus best able to erect and insulate – provide water for baths, and keep it heated if possible. Provide areas near your feeders where vegetation is dense enough to still the wind, and put up birdhouses or structures where your little feathered friends can cuddle up next to other, maximizing their metabolic outputs. (On very cold nights, birds have been observed in “interspecies huddling,” likely preserving heat and survival odds.)
It takes food and feathers to get these critters (from whom we derive so much pleasure) through the cold season. A thoughtful feeding area helps them maximize the use of each.
Here in Washington, Kittitas County Audubon’s Christmas Bird Count is next weekend, by the way, and you may still be able to play. Call Gloria Baldi at 509-933-1558.
Okay, Homey, go talk to that little girl.
