Willow ptarmigan a range of lower plant species. It is also believed that the greening of parts of the Arctic is affecting Willow Ptarmigan populations by altering the shape and size of the shrubs they are able to feed on. Male willow ptarmigans are territorial birds. Males arrive in the breeding areas and set up territories in April and May, aggressively defending them against male interlopers. When the females arrive a few weeks later, the male performs courtship displays such as aerial manoeuvres, strutting and tail-fanning. When she has chosen a mate and a nesting site, the female lays a clutch of
White-tailed ptarmigan season, while willow catkins, mountain avens flowers, and chickweed blooms, other flowers and leaves, lichens and berries form the majority of the ptarmigan's diet in the summer. Once fall and winter arrive in the region, the ptarmigan feeds on pine needles, seeds, willow and alder buds and twigs. Winter food sources have a much higher cellulose content than does summer forage, so the ptarmigan relies on bacteria-aided digestion in the cecum to extract essential nutrients. During the summer, the ptarmigan eats grit to assist in digesting plant material. White-tailed ptarmigan males are usually monogamous and remain with the same mate