How to help chickadees survive winter

Chickadees don't have opposable thumbs. They don't have a Congress. Those handicaps aside, they've done well for themselves accommodating the world.

In turn, there are a couple of things you can do to accommodate these year-round residents and make winter easier for them.

Chickadees run hot — 104 to 108 degrees — and light — one-third of an ounce, the weight of three paper clips. Yet that much warmth does not easily heat so little mass. Surface-to-volume ratio is the problem. Chickadees lose heat rapidly because that ratio is high.

Consider a one-inch square cube, our chickadee stand-in. It has six square inches of surface and one cubic inch of volume, a 6-1 ratio. Consider a bird twice that size. A white-breasted nuthatch comes close. Call it a two-inch cube. That bird has eight cubic inches of volume vs. 24 square inches of surface, a 3-1 ratio. So the chickadee has twice the opportunity for heat loss as its feeder mate.

A perched chickadee has a heart rate of around 520 beats per minute. As bird body size decreases, heart rates generally increase. The heart rate and the volume problem boost the need for food.

A chickadee will eat food equal to about a third of its weight each day. Blue jays weigh 100 grams, but need only 10 grams — 10 percent of its weight — of food daily to keep warm and active.

Digestion in a chickadee is rapid, leaving its stomach empty in as little as 30 minutes. Feeding is most brisk toward the end of the day. Weight gain during daylight hours is shivered away at night, but that involuntary muscle action generates heat.

Shelled sunflower seeds — the bare kernels — allow the bird to eat more efficiently. Hacking open the shell takes energy the bird could use for heat. Chickadees don't have the shell-crunching bills of larger birds such as cardinals.

Chickadees almost never open or eat the seed at the feeder, at least not in our yard. The bird flies to a sheltered perch where it grips the seeds with its toes and begins hacking. They seek shelter to lessen the chance of predation while concentrating on the seed.

Cover of some sort near the feeder will make it more attractive, and safer for the birds to use. We're fortunate to have trees no more than 20 feet from our two feeder assemblies. The birds go back and forth, back and forth.

Wild birds seek variety in food. Chickadees comb tree bark and other cracks and crannies for spider eggs and insects.

Food choice is essential if a single food source disappears. The birds coming to your feeder find on average 20 to 25 percent of their daily nourishment there. Empty feeders will not be fatal to your birds.

Put grit out with the food you offer. Eggshells should be boiled for 10 minutes (then dried) or baked for 20 at 250 degrees before being crushed. This removes the small chance of salmonella poisoning.

Exposure to cold wind sucks heat away so small birds seek shelter at night. Chickadees use cavities, like woodpecker holes.

A nest box turned upside down and with a dowel for perching mounted inside can offer shelter. This way the entry hole is low and heat rises. The box should be located where natural cavities might be found.

Lifelong birder Jim Williams can be reached at woodduck38@gmail.com. Join his conversation about birds at www.startribune.com/wingnut.