Large, found along streams in forested hills and mountains. Dark purple with tiny silvery spots on head, back, and wings. Bill color varies with range: dark in central and eastern China and parts of mainland Southeast Asia, bright yellow in populations elsewhere. Frequently fans tail while standing on an exposed perch such as a waterside rock or overhanging branch. True to its name, it does whistle: a long piercing note that carries well over the sound of rushing water.