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. Cold adaptations The willow ptarmigan has several behavioral and physiological adaptations that help it survive the long Arctic winter, such as large pectoral muscles that aid in the process of shivering. Researchers have found that these pectoral muscles grow quickly during the first few days of the ptarmigan’s life, meaning that the ptarmigan chicks go from having no thermoregulatory ability at hatch to being able to maintain their normal body temperature for hours at 10 °C when they are two weeks old. The rapid increase in pectoralis size is caused by increases in muscle fiber diameters (hypertrophy), and cold exposure is not necessary for this muscle development to occur. Ptarmigan also have thick plumage with feather barbules that contain air-filled cavities, contributing to a low heat loss, which aids in thermoregulation while the bird is roosting in burrows in the snow. Ptarmigan can withstand the severe cold because the ambient temperature in the sheltered microclimate of their snow burrows typically exceeds their lower critical temperature. Status Widespread and not uncommon in its remote habitat, the willow ptarmigan is classified as a species of "Least Concern" by the IUCN. This is because, even if, as is suspected, numbers are declining slightly, it has a very wide range with a total population estimated at forty million individuals. Title bird The willow ptarmigan was adopted as the state bird of Alaska in 1955. It is also the regional bird of Southern Lapland. See also Chicken, Alaska was originally going to be named "ptarmigan" in 1902, but town founders could not agree on how to spell it. References External links Game & Wildlife Conservation Trust Red Grouse Page RSPB Red Grouse Page Video clip of male Willow Ptarmigan in winter Stamps: Willow Ptarmigan (for Belarus, Canada, Finland, Ireland, United States) with worldwide RangeMap Willow Ptarmigan videos on the Internet Bird Collection Willow Ptarmigan photo gallery VIREO willow ptarmigan Grouse Holarctic birds willow ptarmigan willow ptarmigan Symbols of Alaska