The white-tailed ptarmigan lives at high elevations on mountains that receive a lot of snow in the winter. During the summer, the ptarmigans’ feathers are mottled brown. The birds lose the brown feathers and grow a new set of white feathers during the winter. Scientists are concerned that rising global temperatures will affect the white-tailed ptarmigan. If global climate change leads to the elimination of snow in the habitat of white-tailed ptarmigans, which adaptation is most likely to occur over many generations?