White-tailed ptarmigan entry into the respiratory tract. The most obvious adaptation is this bird's cryptic coloration, which enables it to blend in with its environment and avoid predation by golden eagles or other birds of prey. To conserve energy during the winter months, the ptarmigan avoids flight as much as possible and roosts in snowbanks. The white-tailed ptarmigan is listed as being of "Least Concern" by the International Union for Conservation of Nature. This is because, although populations may be in slight decline, its range is too wide and the total number of birds too large to fit the criteria for being
Winter white dwarf hamster able to sense a directional change in photoperiod length, such as in one experiment that demonstrated a transition from 16 hours of light to 14 hours initiates a change to the winter coat. The change to the winter coat can be triggered in the summer by the short day lengths. The change occurs back to the summer coat in the autumn, when the length of the days change again. At internal temperatures hamsters in captivity start later with the changes. The winter colour is less pronounced in them. The eyes of the Winter white hamster are black, unless it is