Winter Recreation and White-Tailed Ptarmigan: An Occupancy Survey on Guanella Pass
About 45 miles west of Denver at Georgetown begins the Guanella Pass Scenic Byway — a 22-mile stretch of highway that puts on display some of Colorado’s most iconic ecosystems. From the dense stands of pine, spruce and fir trees at lower elevations, you’ll rise to meet meandering streams cutting through alpine meadows, eventually reaching the top of the pass that summits above the timberline. This upper portion of the pass sits at about 11,500 feet above sea level in the alpine tundra and supports one of the largest known wintering populations of white-tailed ptarmigan in Colorado.
These birds are the smallest among the grouse family and the only birds in North America that spend their entire lives in the alpine tundra above the treeline. During the summer months, white-tailed ptarmigan plumage is a speckled brown, gray and white, while in the winter they lose any dark coloration and become fully white — except for one small black beak and two small black eyes. Their feet are covered with feathers that stave off the cold while acting as snowshoes in the wintertime to assist with walking. When the temperature drops or the wind picks up, white-tailed ptarmigan keep warm by burrowing up to a foot beneath the snow.
Unfortunately, life for these birds may be getting more difficult. In addition to losing habitat for which they have become so uniquely adapted due to climate change, recreation is one of the most imminent threats to these birds and other wildlife dependent on alpine ecosystems. Because white-tailed ptarmigan lead a sedentary lifestyle in the winter when food sources are not as plentiful, any extra requirements to move around the landscape can be detrimental to their survival. And because of a wintering ptarmigan’s energetics — i.e., the particular way in which ptarmigans acquire and expend energy — they may be more susceptible to human disturbance.
The winter season is a popular time for snowshoers, skiers and hikers, and Guanella Pass is a popular spot for these types of activities. The most traversed trail on the pass during the winter takes recreationalists to the top of Mount Bierstadt, bisecting an essential core habitat area for white-tailed ptarmigan.
Colorado Parks and Wildlife (CPW) personnel have observed a marked increase in recreation in recent years — particularly noticing more snowshoe tracks weaving through this crucial territory for wintering ptarmigan. As a result of the noted increase of recreation on Guanella Pass, CPW biologists Rebecca Boyce, Lance Carpenter and Mark Fisher have launched a project to evaluate the efficacy of occupancy surveys that can be used to distinguish a change in the distribution of white-tailed ptarmigan found in winter core habitats caused by recreational activities over time.
On a Monday in late February, a day of surveys began at 8 a.m., when lead biologists and volunteers gathered to review the day’s goals and protocol before moving out into the field. Core habitats for the ptarmigan have been divided into four zones containing 365 randomly generated plots measuring 70 square meters with a 100-meter buffer between them.
As teams of two set out on a survey, one person moves out first while the other waits about 30 minutes before following — allowing a plot to be independently surveyed twice. Each plot receives 12 minutes of time to be surveyed by each independent observer, during which they look for ptarmigan or any sign of them (burrows, tracks or fecal droppings). Should a bird or any indication of its presence be found before the 12 minutes expires, the observer immediately moves on to the next plot.
Surveyors also carry tape measures to gather an average height of any exposed willow branches, the buds from which are a white-tailed ptarmigan’s primary source of food during the winter months. If no bird or sign is observed within the 12 minutes, the surveyor moves on to the next plot until finished.
The data collected here can be expected to help alleviate pressures on ptarmigan by being better able to inform the general public of their presence and how people can help nurture the surrounding wildlife and landscape by practicing respectful recreation. Simple actions, such as staying on designated trails, keeping dogs on leashes and providing wildlife with ample room to move, can go a long way toward conservation as well as personal safety.
Written by Ryan Jones. Ryan is a visual coordinator for Colorado Parks and Wildlife.