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The Guam Rail (Gallirallus owstoni) is a flightless bird, endemic only to the United States territory of Guam. In the Chamoru language, used on Guam, it is known as Ko'ko'. Before 1960 it was common, though it has a secretive lifestyle living in scrubby secondary growth or mixed forest. The Guam Rail disappeared from southern Guam in the early 1970’s and was extirpated from the entire island by 1987 due to the accidental late-1940’s introduction of the brown tree snake Boiga irregularis. Department of Agriculture biologist Bob Beck found that Guam rails breed well in captivity and established a breeding program which keeps birds at the Division of Aquatic and Wildlife Resources on Guam and at 15 mainland U.S. zoos. Captive grown rails were reintroduced to Guam in 1998 with no long-term success, and subsequently introduced to the snake-free island of Rota (Northern Mariana Islands), where two small breeding populations were able to persist despite hunting pressure from feral cats. In 2011 birds were also introduced to the island of Cocos, where they appear to be breeding.
The Guam rail is a medium-sized rail about 28 cm (11 in) in total length. The body is elongated and laterally compressed, particularly in the neck and breast regions, allowing the birds to move rapidly through dense vegetation. Males are slightly larger than females but have similar appearance with brown head and back, a dark breast barred with white, grey eye stripe and dark brown legs and beak. Gallirallus owstoni are generalists; they eat slugs, snails, lizards, insects, carrion and plant matter such as seeds, leaves, flowers and grasses. They nest year-round on the ground, with a usual clutch size of 3-4 eggs. They are territorial, usually silent but will give a loud whistle or series of whistles in response to the call of another bird or a disturbance. (BirdLife International 2012; Fritts and Leasman-Tanner 2001; Wikipedia 2013)