It has pure white plumage in winter, except for a black tail, which is present in both sexes year-round. 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.