WHITE-TAILED PTARMIGAN} Lagopus leucura
DESCRIPTION: Adult white-tailed ptarmigan typically grow to 30 to 34 centimeters in length and weigh 345 to 425 grams. The bird is distinguishable from other species of grouse by its perpetually white tail feathers. The rest of the ptarmiganís plumage changes seasonally, from a predominantly grayish brown during the summer to completely white during the winter, with both plumage patterns providing seasonally relevant camouflage in the ptarmiganís high-alpine environment. The white-tailed ptarmigan also exhibits feathers on its feet that serve as a sort of snowshoe. Male and female birds can be distinguished from each other during the summer by the color of their eye combs, breast feathers and plumage.
HABITAT: The white-tailed ptarmigan is found almost exclusively in alpine environments at or above the tree line, which occurs where vascular plants reach the limits of their ability to withstand adverse seasonal conditions. Alpine ecosystems are characterized by varied topography, soil type and slopes; they experience high winds, a short growing season and intense solar radiation. Alpine vegetation includes small patches of plant communities that consist of low-growing perennial forbs, graminoids, mosses, lichen and dwarf shrubs.
RANGE: The ptarmiganís primary range extends from southeastern Alaska, the Yukon, and the Northwest Territories southward through British Columbia and the western border of Alberta, to northwestern Montana and the northern Cascade Mountains in Washington. Smaller populations are fragmented throughout suitable alpine environments in the Rocky Mountains of Montana, Colorado and northern New Mexico; the bird has disappeared from Wyoming and areas in New Mexico. Additionally, populations have been introduced into high-alpine habitats outside the ptarmiganís historical range, including in the Sierra Nevada in California, the Uinta Mountains in Utah, Pikeís Peak in Colorado and the Pecos Wilderness in New Mexico.
MIGRATION: Female white-tailed ptarmigan migrate, individually or in flocks, from their winter habitats at or just above the tree line into higher-elevation territories established by males. Males will often return to territories they occupied during the previous year.
BREEDING: Breeding takes place in the spring, with nesting occurring as the snow melts, usually in early to mid-June. Females will typically lay one clutch of four to eight eggs, with a possible later clutch of two to six. Females care for the eggs during an incubation period of 22 to 26 days, soon after which females will lead their young away from the nesting area and to slightly higher-elevation summer habitat, where they mix with other broods as well as males and unsuccessful females, forming larger flocks. The mixing of broods and subsequent migration to winter habitat separates broods from their mother.
LIFE CYCLE: The maximum lifespan of white-tailed ptarmigans is three to four years.
FEEDING: The white-tailed ptarmiganís spring and summer diet is composed primarily of the plant genera Salix (willow), Ranunculus (buttercup)and Dryas (mountain-avens). Other plants are eaten in Alaska, Canada, Washington and the Rocky Mountain range ó the last of which provides the most diverse diet for the bird. Ptarmigan rely primarily on willow during the winter. Invertebrates are consumed by fledglings younger than three weeks but are absent in the diet of adults.
THREATS: The primary threat to the white-tailed ptarmigan is global warming. The bird and its habitat are also threatened by recreation (skiing, off-road vehicles and hiking) that disturbs its alpine habitat, mining activities, and livestock grazing, hunting, disease and predation.
POPULATION TREND: Population trends for white-tailed ptarmigans vary by region and in some cases are not known; however, population extinctions of the bird have already occurred and climate change will likely increase their occurrence.