2019-02-09 / Columnists

Nature Notes

Bird Species Employ Various Techniques To Survive Winter Cold
By Patricia Martin

As anyone who has been around the Midwest and Great Lakes region knows, last week was cold. After a mild beginning of the winter, the temperatures took a nosedive and the high winds compounded the problem. Monday, January 28, I awoke to ambient temperatures of minus 15 degrees Fahrenheit with east winds between 20 and 30 miles per hour gusting to 40 miles per hour. It was cold and miserable. About midmorning, I looked out my window at the apple tree in my yard where my bird feeders hang (before the cold weather struck, I made sure that the feeders, both the suet and seed, were stocked full). In the middle of the cold and wind, there was my faithful pair of northern cardinals. For a while the bright red male was on the feeder and the more yellow female was on the tree and then they reversed their positions. As the cold weather continued, blackcapped chickadees, nuthatches, mourning doves, and downy and hairy woodpeckers stopped by, braving the cold and storm.

A cardinal on a perch this winter. (Photographs by Clark Bloswick) A cardinal on a perch this winter. (Photographs by Clark Bloswick) I began to wonder at these birds. I thought that instead of hanging out at the feeders, they might have been hunkered down somewhere trying to keep warm like the rest of us. I began to think about strategies birds might have for surviving these cold Mackinac winters. Research began, and the following is some of what I found.

First, many of our feathered friends (along with some of our human ones) just leave and go on epic journeys to warmer climates to spend the winter. But every year, some species of birds stay put and maintain their territory year-around. Doing so allows them to avoid the hazards of migration, but in exchange they have to endure the cold and storm.

Birds are warm-blooded and so must maintain their bodies at a constant temperature, which is often about 106 degrees Fahrenheit. Different birds have evolved different strategies to make and maintain their body temperature.

Ducks gather on a rooftop. Ducks gather on a rooftop. Some birds get together with some friends, especially in bad weather in the winter. In the winter, birds are often seen in flocks for several good reasons. In a flock, it is much less likely that a predator would be able to sneak up on you because there are more eyes on the lookout. Some species, like sparrows, seek out shelter in dense foliage or huddle, bunching together to share warmth.

Getting out of the wind is really important in cold weather. If the wind is blowing, many birds will go to the other side of the tree or find a spot out of the wind, in the lee. The other day when I was watching the cardinals in my yard, I realized that where the feeders are located is protected from the east wind by the house.

In the winter birds really have to eat as much as possible, and so they will often park themselves by the feeders or some seedy plants or wherever food is available and chow down. Foods with lots of fat are preferred, so things like black-oiled sunflower seeds and suet are particularly popular. You may have noticed that one species may eat for a while and another will swoop in and chase it away or the first one may stand its ground. It is one reason I have multiple feeders. Fat that the birds put on is both an insulator and an energy source. In some species, like the chickadees and finches, more than 10% of their winter body weight may be fat. Much of the daylight hours are spent getting food.

Another strategy for surviving the cold is to find a comfortable resting place, out of the wind, and puff up the feathers. The food that has been eaten produces heat, which needs to be conserved, and puffing up the feathers helps do this. Feathers keep the cold air out and the downy feathers trap the warm air near the body so it doesn’t dissipate. Many species grow an extra set of insulating downy feathers. Large birds like geese and grouse do this. It is interesting to note that woodpeckers don’t have any downy feathers. You may also see puffed up birds, minimizing the surface area exposed to the cold by tucking in their head and feet. The cardinals are particularly good at puffing up and are easy to spot. Mourning doves also exhibit this behavior and often just look like a ball of feathers.

When not foraging for food, many birds find a nook they can fit in that is small enough that you can warm it up with any heat that does escape. Woodpecker cavities, crannies beneath the eves of houses, and tunnels in the snow are all warmer than spending time out on a limb in the wind.

Many birds have the ability to keep their vital organs warm in extreme cold by circulating warm blood near them while allowing extremities to cool down. Gulls are a good example of this adaptation. They can stand on ice with feet at near-freezing temperatures while the core of their body stays nice and warm.

Chickadees and other small birds can’t put on too much bulk or they won’t be able to fly. They instead shiver, which is different than mammal shivering (they don’t tremble). They instead activate opposing muscle groups, which create muscle contractions, but without the jiggling humans do. This form of shivering is better at retaining the bird’s heat.

Keeping warm during daylight hours is one thing, but keeping warm at night is another. Many birds have adapted to the cold by lowering their body temperatures moderately to reduce their metabolism, which reduces energy use. Most birds that winter over do not go into true torpor because it would take too much energy to warm up in the morning. Birds, like the black-capped chickadee, reduce their body temperature at night as much as 22 degrees Fahrenheit in a process called regulated hypothermia.

These are but some of the ways that our birds survive the cold and storm of our Mackinac winters. You can help them, as many of us do, by providing food for them in feeders. It helps our feathered friends survive the cold, and watching them is a good form of entertainment.

Trish Martin is a year-around resident of Mackinac Island, has earned a master’s degree in botany from Central Michigan University, and owns Bogan Lane Inn.

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