White-tailed ptarmigan than forest grouse, but still prefers running to flying. It ranges from Alaska and western Canada south to northern New Mexico. Males return from their wintering areas to establish territories on spruce-willow timber line breeding grounds in April. Females arrive in early May and pairs are formed. The white-tailed ptarmigan is the only bird in North America to reside permanently in the alpine zone. Its habitat includes areas of boulders, krummholz, snowfields, rock slides, frost-heaved soil and upland herbage. Even in winter it stays in high valleys and mountain slopes where alder, willow, birch and spruce poke through the snow
Arctic ice pack Arctic ice pack The Arctic ice pack is the sea ice cover of the Arctic Ocean and its vicinity. The Arctic ice pack undergoes a regular seasonal cycle in which ice melts in spring and summer, reaches a minimum around mid-September, then increases during fall and winter. Summer ice cover in the Arctic is about 50% of winter cover. Some of the ice survives from one year to the next. Currently 28% of Arctic basin sea ice is multi-year ice, thicker than seasonal ice: up to thick over large areas, with ridges up to thick. As well as the regular