Willow ptarmigan in favourable seasons, many juveniles may survive and the population of willow ptarmigan is prone to wide fluctuations in size. By September, families begin to form flocks. The females and young migrate to lower altitudes and may overwinter from their breeding grounds in wooded valleys and hilly country. The males also congregate in small groups but do not usually travel as far as the females. The willow ptarmigan was adopted as the state bird of Alaska in 1955. Widespread and not uncommon in its remote habitat, the willow ptarmigan is classified as a species of "Least Concern" by the IUCN.
Rock ptarmigan the Russian High Arctic overwinters during the polar night and survives by feeding on rich vegetation on and underneath high cliffs where seabird colonies are located in summer.<ref name="FJL/">Dinets, V. (2001) Winter ecology of Willow Ptarmigan "Lagopus lagopus" and Rock Ptarmigan "L. mutus" at the northern limit of their range. "Ornitologia" 29: 326-327 (in Russian with English summary).</ref> During the last ice age, the species was far more widespread in continental Europe. The rock ptarmigan feeds primarily on birch and willow buds and catkins when available. It also eats various seeds, leaves, flowers, and berries of other plant species. Insects