Curious Nature: ‘Snow chickens’ right at home in the mountains
January 14, 2012
There’s a lot to love about white-tailed ptarmigan (Lagopus leucurus) in Colorado. For one, they seem to thrive in the snow, just like most of us mountain dwellers, hence the nickname “snow chicken.” They are the smallest of the grouse family of birds, with plump bodies and small heads. Mottled brown in summer, white in winter, they can be distinguished from other similar birds by their year-round white underbodies and tails. They live on alpine mountaintops their entire lives and even show signs of stress if temperatures get too warm.
Most of the population lives in Alaska and western Canada, but there are smaller patches in the Rockies and Sierra Nevada. In Colorado, there is an estimated breeding population of 34,000 birds, enough to allow for a short hunting season each fall. We have the second largest U.S. population, behind Alaska. Ptarmigan hunting can be a challenging exploit, and enthusiasts often plan trips months in advance, for although the birds are not easily spooked, they can be extraordinarily well-camouflaged. In fact, the name for a group of ptarmigans has been termed a “covey” or an “invisibleness.” It makes me wonder if the relatively low snow levels so far this winter could affect their numbers. If the birds molt into their winter white feathers while the ground is dark, they could become easy prey for predators such as hawks, eagles, falcons, owls, foxes and coyotes.
How does such a small bird thrive in the alpine environment? Its diet is composed mainly of shrubs and forbs, especially the leaves, buds and twigs of willow, and it spends winters in willow-dominated spruce krummholz (timberline) habitats. The birds conserve energy and heat at night by roosting in snowbanks and forage mainly around dawn and dusk. They are known to have a unique metabolic ability to gain body mass even through the harsh winter, and a counter-current circulation conserves heat (unlike ours, where warm blood makes a loop through our cold extremities and has to be re-warmed to maintain core temperature). Their feet are feathered during winter, acting and looking much like snowshoes for the ptarmigan. Behaviorally, they spend most of their time on the ground, rather than in flight, and are fairly sedentary. Their lifespan even with these adaptations is only three to four years.
Another reason to love ptarmigans is that they’re an “indicator species” for high-elevation ecosystems. If the birds are doing well, chances are good that the ecosystem is healthy. They are nonmigratory and spend most of their lives within a small home range, generally at higher elevations in summer than winter. Because of their specialization, populations of ptarmigan can be extremely isolated from one another, as there are pockets of suitable habitat with large areas between. This leaves them prone to threats from climate change, especially an increase in average temperatures, which could limit their range to the very highest altitudes, where their food grows. Cadmium that may be mobilized during mining activities has been shown to accumulate in willows and causes poisoning in the birds (and their predators). Because of these and other threats such as human disturbance, the Forest Service listed them as a sensitive species, and in 2010, the U.S. Fish and Wildlife Service filed a petition for protection as a threatened species under the Endangered Species Act.
The future of ptarmigan, a truly unique alpine specialist, depends on us and our ability to protect alpine environments for future generations. With a very keen eye, maybe you’ll spot one blending in against the shrubs, rocks or snow; I know I’ll be on the lookout!
Emerald Gustowt is a volunteer with Walking Mountains Science Center, with a background in avian rehabilitation. While she’s in her alpine habitat, she can also be found in a feather coat, hoping for snow.