Earth Almanac: January/February 2008

Northern Exposure

While other birds flee our northern winter or tough it out, puffed against the icy blast, white-tailed ptarmigans—high in the jagged mountains of Alaska, western Canada, and south to northern New Mexico—can’t seem to get enough of it. Except when feeding on their staple, willow buds, they generally avoid elevations low enough to support trees. No other native bird spends most of its life above timberline.

This, our smallest grouse and the only ptarmigan confined to North America, has adapted to its frigid environment by evolving feathers filled with insulating air spaces, an undercoat of thick down, and feathered nostrils, eyelids, and toes. In addition to serving as insulation, toe feathers (grown in winter) act as snowshoes, increasing the surface area of the foot by a factor of four. At night and during much of the day the birds roost under the snow, where the temperature can’t dip much below 32 degrees Fahrenheit. White-tailed ptarmigans seem actually to be stressed by spring thaws during which they can be seen bathing in snow drifts.

Should you find yourself in their winter habitat (doubtless while helicopter skiing), listen for their soft, low hoots and clucking emanating from flocks that may number as many as 95 birds. And be prepared for them to burst up between your legs, showering you with snow.