Willow ptarmigan with willow and alder trees, heather moors, tundra and mountain slopes. In the winter, females and sub-adults may move to lower altitudes and seek shelter in valleys or in more densely vegetated areas, but adult males usually remain in the subalpine region. The red grouse is common on heather-clad moorland across the north and west of Great Britain and in localised areas of Ireland. The willow ptarmigan has a varied and seasonal diet. The bird is herbivorous for most of its life and subsists on various plant materials. As juveniles, they may feed on insects due to an inability to
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