any of five species of pigeon-sized birds that comprise the family Brachypteracidae (order Coraciiformes) known for their tumbling flight. They are found only in Madagascar. Four species inhabit deep forest; one, the long-tailed ground roller (Uratelornis chimaera), confined to a small desert in southwestern Madagascar, is nearly extinct. Ground rollers range from 30 to 40 centimetres (12 to 16 inches) in length.