Beating winter, in a heartbeat

If you're a black-capped chickadee, you and a buddy could travel anywhere in the United States for 41 cents total, the cost of a first-class postage stamp. At less than half an ounce each, your problem would be getting into the envelope.

Or surviving winter at that weight.

So how do they do it? How do chickadees deal with the cold, with short days and long, colder winter nights?

Birds in general have a higher metabolic rate, body temperature, heart rate and blood pressure than mammals. And smaller birds tend to run at faster rates than larger birds.

Chickadees at rest have a heartbeat of 540 per minute. Their body temperature is about 105 degrees. They take a breath about once a second. Flying increases heart and breathing rates.

If you are a small creature, you lose heat at a faster rate than does a larger creature. You have more body surface relative to mass. To stay alive, you must feed a roaring fire. You need lots of calories, particularly when it's cold.

Each winter day, chickadees must eat the energy equivalent of about 150 sunflower seeds when the temperature is above zero, 250 when it's below zero. When daylight is short, that makes for busy chickadees.

In winter, chickadees split their diet about 50-50 between animal and vegetable, between insects and spiders and seeds and berries. Watch a chickadee work its way around a tree trunk and out to its smallest branches, checking each crack and crevice for insects, pupae and spider eggs.

They'll take fat from dead mammals (or suet). And they forage from first light to last, seeking the most food in the shortest time with the smallest risk.

Many birds will fluff their feathers to trap body heat. They'll tuck one leg to their breast to conserve heat, or tuck their bill into the feathers of a shoulder for the same reason.

When it comes to staying warm, chickadees have a significant trump card. They are one of the few bird species that can lower their body temperature at will. On cold nights, to cut their need for energy, they can reduce their thermostats by about 20 degrees.

Food and water help

Black oil sunflower seeds have a high meat-to-shell ratio (large kernel and a small, thin shell). They're high in fat and very nutritious. The size and shell make it easier for small birds, like chickadees, to handle and crack the seed. You might also consider shelled sunflower seeds, which save the birds the energy needed to open the package.

If you are feeding birds, keep the feeders filled, particularly in cold or stormy weather. Make sure the seed is not covered with snow and the feeder ports aren't clogged with snow or ice. And consider adding a heater to keep your bird bath open all winter.