The Mount Rainier white-tailed ptarmigan is found only in the Cascade Mountains of Washington State and British Columbia, and one of five subspecies of white-tailed ptarmigan in North America.

The bird is one of the few animals that lives on mountaintops throughout its entire life. Well-adapted to life above the treeline, Mount Rainier white-tailed ptarmigan are equipped with feathered, snowshoe-like feet and seasonally changing plumage. The scientific name for this genus of birds, Lagopus, actually means hare-foot, as in snowshoe hare. During the winter months, the birds are excellently camouflaged into the snow with white feathers that will turn to a mottled brown by summer to blend in with alpine rocks and tundra. Adult birds are herbivorous, only eating plants found in its high-elevation domain, including dwarf huckleberry, heathers, and saxifrages. 

It is estimated that the range of the subspecies extends from the Fraser Valley in British Columbia, south along the Cascade Range to Mount Adams. White-tailed ptarmigan regularly occurred on Mount St. Helens before the volcano erupted in 1980. Subsequent to the eruption, only three white-tailed ptarmigan occurrences were reported from that area, and none have been reported since 1996.

With its habitat being limited to mountaintops in the Cascade Range that effectively act as islands, climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.

Learn more about climate change poses a significant threat to the ptarmigan. Warming temperatures and decreases in snowpack are expected to diminish its high-elevation home as the vegetation changes, treelines climb, and the bird's pockets of refuge disappear.