Sleek, secretive diving duck with a bright orange-red bill and a long, shaggy crest. Relatively rare East Asian endemic. Male has a glossy green head and a black-and-white back. Female has a rusty brown head and gray back. Both sexes have prominent dark-edged white “scales” on the sides that distinguish them from other merganser species. Breeds in cavities along forested montane rivers and winters on fast-flowing rivers and lakes.