The Guam rail (Gallirallus owstoni) (Chamorro name: ko'ko' ) is a species of flightless bird, endemic to the United States territory of Guam. The Guam rail disappeared from southern Guam in the early 1970s and was extirpated from the entire island by the late 1980s. This species is now being bred in captivity by the Division of Aquatic and Wildlife Resources on Guam and at some mainland U.S. zoos. Since 1995, more than 100 rails have been introduced on the island of Rota in the Commonwealth of the Northern Mariana Islands in an attempt to establish a wild breeding colony. Although at least one chick resulted from these efforts, predation (largely by brown tree snakes and feral cats) and accidental deaths have been extremely high. A small number of birds potentially persists.