Bison whistles are small wooden instruments used to attract various fauna in the World of Avatar. They are the only known instruments capable of calling flying bison from long distances. These antique whistles are thought by many to be worthless, but they were once used by the Air Nomads to herd their bison. Bison whistles produce sound waves too high in pitch to be picked up by human ears, and as such, are only noticeable to certain animals who can hear the high frequency and pinpoint its origin. They vary tremendously in design.