1、The ptarmigan is well-adapted to the harsh Arctic environment with its white feathers in winter.

北极雪鸡在寒冷的北极环境中具有白色的羽毛，很适应这样的环境。

2、Ptarmigans change their plumage to blend in with the changing seasons and camouflage themselves from predators.

北极雪鸡通过改变羽毛来适应季节的变化，并且能够隐蔽自己，躲避捕食者。