Birds in Cold Weather

Joe Meche is a member of the board of directors of the North Cascades Audubon Society and is in his ninth year as editor of the chapter newsletter. Joe is also a member of the board of directors of the Washington Brant Foundation. He has been photographing birds and landscapes for over 30 years and has been watching birds for more than 50 years.

Humans have always been in awe of the massive seasonal migrations of animals. The basic concept of migration in fall and winter is to travel to a climate that is more tolerable and provides all the necessary elements to survive away from the colder, shorter days of the northern latitudes. Many species of birds cope with winter weather by migrating and spending those months in more hospitable climes. (As a matter of fact, many humans spend their winters farther south and have become known as snow birds. It’s sort of like anthropomorphism in reverse.) On the other hand, not all birds migrate.

As you sit in your home on cold winter days, as snug as bugs in your respective rugs, do you ever wonder about the birds that frequent your feeder or those that you see flying about, especially on these recent wintry days? Why don’t they migrate farther south with other birds? The birds that you see are quite simply a small sample of the millions that weather the cold on days when you’d rather not venture too far from the hearth. The small but hardy seed eaters that make up a good number of the birds that we see at our feeders throughout the winter are prime examples. Birds are outside 24/7, regardless of the rain or sleet or gloom of night. More than a simple question of why they do it, is how they do it.

Perhaps the single most important factor in where birds choose to spend the winter is the availability of their preferred food. Their survival depends on the food they consume to maintain adequate body temperatures during the long, cold nights. Birds that winter in colder climates must eat almost constantly during the day to stay ahead of the metabolic curve. Birds need to eat richer foods in winter to heighten their metabolism, and some birds even have the ability to pack seeds into their crops, which slowly digest through the night.

Birds that normally remain in colder areas, like snowy owls, will take part in mass irruptions if their specific food requirements aren’t met. If the supply of lemmings or mice is short or there’s too much competition for food, the owls will move to a new area. The cold, in this case, is not as much of a direct factor as the food supply. This winter, in fact, uncommon species have been showing up in the lowlands, possibly because of something that might be out of synch in their usual winter habitats.

We know that birds are wonders of adaptive design in innumerable ways, but their innate ability to cope with weather extremes is one of the most challenging for humans to comprehend. Who hasn’t looked out onto a winterscape of ice and snow, in awe of the birds that are out and about in search of food? Why are the feeders filled with chickadees and juncos, and any number of other species that chose not to head south? We look onto this scene from behind insulated glass windows, with the heat tuned to maximum comfort, and those amazing birds are flying and hopping about!

As humans evolved, we became less tolerant of the elements and more dependent on rudimentary shelter and clothing. Our shelter and clothing have certainly evolved along with us, as evidenced by the fact that we can hardly tell if it’s cold outside without actually going outside. Our clothing, with layers upon layers creating a bit of bulk, is geared to protecting us from whatever the weather might be. We have, in effect, left our origins behind and collectively come to lead a mostly sheltered life. We have come so far, in fact, that we can’t go back!

Birds, on the other hand, are remarkably adaptive to the most extreme conditions. In a previous “Beaks and Bills” column, we discussed feathers and their role as insulation for birds, both in summer and in winter. Contour feathers are paramount to keeping birds warm, but a layer of down feathers underneath is even more important. Some northern birds have dense down, while birds that winter in the tropics do not. Birds are able to fluff their feathers to provide a layer of dead air to increase the insulation value of the feathers. Most birds also sleep with their bills tucked under their feathers, providing them with warm air to breathe and reducing the amount of surface area exposed to the cold.

Other factors come into play to enable birds to survive cold nights. For starters, the avian metabolism plays an important part in that diurnal birds are inactive at night and are able to lower their body temperatures slightly during that time to reduce heat loss. Many species form group sleeping arrangements and huddle together for warmth. Some smaller species are known to form veritable feather balls to share body heat during the night. A friend reported once that she observed more than 30 winter wrens flying into a single nesting box above her veranda. This routine was repeated on cold nights as the wrens joined forces to stay warm.

Other birds adapt to the cold with a number of learned survival techniques. Some species plunge into snow banks where the temperature is milder than the air temperature, while others seek shelter in dense vegetation or natural cavities where the effects of cold wind and low temperatures are less severe. Birds, again, are always showing their remarkable ability to make the best of the situation.

T.W. Higginson (1823-1911), Civil War veteran, naturalist and contemporary of Emily Dickinson, had a noted appreciation for birds and especially for their natural ability to withstand the rigors of winter. Here is an excerpt from “Our Birds, and Their Ways,” published in 1857.

“The truth is that birds are remarkably well guarded against cold by their quick circulation, their dense covering of down and feathers, and the ease with which they can protect their extremities. The chickadee is never so lively as in clear, cold weather—not that he is insensible to cold; for on those days when the mercury falls to fifteen or more degrees below zero, the chickadee shows by his behavior that he, too, feels it to be an exceptional state of things. Of such a morning I have seen a small flock of them collected on the sunny side of a thick hemlock, rather silent and quiet, with ruffled plumage, like balls of gray fur, waiting, with an occasional chirp, for the sun’s rays to warm them up, and meanwhile not depressed, but only a little sobered in their deportment, and ready, if the cold continued, to get used to that too.” §