Both sexes are barred with nondescript brown and black markings in summer, with females more coarsely marked than males. Males wait longer than females to shed the white plumage in the breeding season. This is part of the courtship display, but also leads to heavier predation of males by gyrfalcons. Males have a black streak from beak to eye, a scarlet comb near the eyes, and are generally pale on the upper body in fall. Some, but not all, females show the black eye streak.
Females are nearly invisible against the tundra in summer, and are slightly smaller than males.
All ptarmigans have feathered feet, which act as snowshoes, allowing the birds to walk in soft snow. The feathers may also increase insulation for these year-round arctic dwellers. Major summer diet is a mixture of plant material, especially blueberries, horsetail tips, crowberries, mountain avens, and heads of sedges. Winter foods are mostly buds and catkins of dwarf birch, and some willow buds and twigs. Nesting habitat is most often a bare rocky outcrop with little vegetation.