Willow ptarmigan (Lagopus lagopus)

All three species of ptarmigans—a genus of birds related to grouse, chickens, and pheasants—trade their scalloped brown plumage for white feathers. (They spend spring and fall in a mottled state, matching the patchy snow cover.) The white-tailed ptarmigan (Lagopus leucura) turns entirely white, while the willow ptarmigan (L. lagopus) and rock ptarmigan (L. muta) retain some black feathers in their tails. Ptarmigans even develop white boots to match; the downy foot covering also helps them to walk atop the snow. The air bubbles in their winter feathers—which may help with insulation—scatter light, making them appear more brightly white than other white birds.