Black-billed species ( Cygnus cygnus buccinator ) of swan , named for its far-carrying, low-pitched call.
About 6 ft (1.8 m) long, with a 10-ft (3-m) wingspan, it is the largest swan, though it weighs less than the mute swan. Once threatened with extinction (fewer than 100 were counted in the U.S. in 1935), it has made a strong comeback; though still listed as vulnerable, its population in western Canada and the northwestern U.S. now exceeds 5,000.