The Columbia Encyclopedia, Sixth Edition. Columbia Encyclopedia World Factbook American Heritage Coll.
American vultures have no syrinx and are thus voiceless, emitting weak hisses.
Most vultures have dark plumage and small, naked heads. Vultures have keen sight and are effortless soarers, skillful at riding the thermal updrafts of their mountain habitats. They are normally solitary but will gather in crowds to feed. As valuable scavengers they are protected by law. Vultures are frequently called buzzards, although the name is more correctly applied to hawks of the genus Buteo.