White-tailed Ptarmigan, the smallest grouse in North America, inhabits alpine habitats from timberline to the high alpine in the mountain cordilleras of the West. This ptarmigan has been recorded nesting at elevations up to 4,054 m, making it North America's third highest elevation breeding bird after Horned Lark (Eremophila alpestris) and Rosy Finch (Leucosticte spp.) (KM, Martin 2014). It is the only bird in North America that remains exclusively in alpine or upper subalpine habitats year round.
Physiological, behavioral, and life history adaptations that conserve energy and enhance its ability to “disappear” into its habitat have allowed this ground-nesting herbivore, which subsists on buds, leaves and flowers of low shrubs and herbs, to thrive in its open, cold, and sometimes arid and hypoxic alpine environments. In winter, for example, flocks are known to roost within snowbanks and individuals develop feathered tarsi that function as “snowshoes.” They generally walk rather than fly, and in poor weather select microhabitats several degrees warmer than ambient temperature. In addition, these birds tolerate a wide range of temperatures without expending excess energy. Ptarmigan are always watchful for predators; they can detect predators at great distances and choose locations that render them almost invisible in all seasons, or they remain near rocks for escape cover.
Like its arctic congeners, the Willow Ptarmigan (L. lagopus) and Rock Ptarmigan (L. muta), the White-tailed Ptarmigan is noted for plumage that changes from white in winter to grayish brown in summer, such that it is molting feathers for 8 months of the year. This is the southernmost species of ptarmigan, with populations extending from s.-central Alaska and n. Yukon to n. New Mexico, a distance of about 4,370 km, and a latitudinal range from 67°to 35° N. Because alpine areas have remained relatively undisturbed, this species still occupies most of its historical range.
The word ptarmigan comes from the Scottish Gaelic tàrmachan (1590s), literally croaker (Lockwood 1993). The silent initial p was added in 1684 by Robert Sibbald through the influence of several Greek words, especially pteron, meaning wing, feather or pinion. The genus, Lagopus, is derived from lagos, meaning "hare," + pous, "foot," in reference to the bird's feathered legs in winter. The species name leucura is derived from the Latinized version of the Greek leukos, meaning "white," and oura, meaning "tail," in reference to the bird's white tail year round (Terres 1980). The word ptarmigan always should be used in the singular.
The challenges of accessing and working in their alpine habitat have hindered detailed examination of White-tailed Ptarmigan life history in many parts of its range. The longest field study of the population ecology of White-tailed Ptarmigan of L. l. altipetens started in 1965 on Mt. Evans, Guanella Pass, Loveland Pass, and Rocky Mountain National Park, Colorado (continue to present, CEB, and colleagues). KM has also conducted field studies in Colorado and on the coastal subspecies L. l. saxatilis on Vancouver Island, British Columbia, 1995–2004, with Citizen Science observations of adults and broods received from 1995 to the present (2015). Recent field studies on L. l. leucura were conducted in the Ruby Range Mountains, near Kluane Lake in sw. Yukon, where the species occurs sympatrically with Rock and Willow ptarmigan (2004–2008, SW, KM, and students). Ptarmigan populations have also been monitored in Glacier National Park (Montana), first by T. S. Choate from 1958 to 1962, and later by David Benson, 1995–1999 and 2009–2013; Benson 2011); in the Sierra Nevada, California by Jennifer Clarke, 1985–1987 and 2002–2003 (Clarke 2010); and in several locations in the Cascade Range of Washington State by Michael A. Schroeder.
The overall results from these ecological studies across the range of the species reveal impressive variation in life history traits and morphology, and exceptional abilities to resist extreme environmental gradients in time and space. The extraordinary abilities of White-tailed Ptarmigan to adapt to their challenging alpine habitats begin with the ability of ptarmigan embryos to develop normally above 4,000 m, in hypoxic conditions where most other bird species would be unable to sequester enough oxygen for normal tissue maintenance. These wily herbivores continue to impress and intrigue researchers and ornithologists with their cryptic plumage and “tame” behavior.