Critically Endangered
Guam rail
Hypotaenidia owstoni
The Guam rail (Gallirallus owstoni), known locally and in Chamorro as ko'ko', is a small, terrestrial bird endemic to Guam in the Rallidae family.
Appearance
Adult Guam rails are monomorphic, meaning males and females have the same plumage and characteristics. The head and back are brown. It has a grey eye stripe and throat, a dark blackish breast with white barring, and the legs and beak are dark brown.
Guam rails have underdeveloped wing muscles and are considered flightless, though they can fly about 3 to 10 feet (1 to 3 meters) at once.
Guam rails are a medium-sized rail species, growing to about 11 inches (28 cm) in total length. Adults will weigh around 7 to 12 ounces (200 to 350 grams).
Range and habitat
Historically, the rail was found only on Guam. The island covers about 132,230 acres. According to a 2013 survey, about 53% of the island is forested.
The 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.
GBIF currently lists 8 occurrence points. Those points follow where people logged the taxon — museum drawers and surveys included — not a closed range boundary.
Pins are Wikidata “endemic to” fields. Orange dots, when present, are GBIF occurrence tiles — survey bias included.
Diet and breeding
Guam rails are omnivorous foragers known to consume gastropods, insects, geckos, seeds, and vegetable matter. A large part of their diet consists of giant African snails, that were introduced to Guam around 1945 and became an easy food source for the birds.
Guam rails have been observed foraging and hunting. When foraging, they peck food from the ground and eat seeds and flowers from grasses. It is a year-round ground nester and lays 2–4 eggs per clutch, and both parents share in the construction of a shallow nest of leaves and grass.
In crisis
The species became extinct in the wild in the early 1980s when biologists captured the remaining wild population to establish a breeding program. In 2019, they became the second bird species to be reclassified by the International Union for the Conservation of Nature from Extinct in the Wild to Critically Endangered. Once introduced to Guam, the snakes thrived off an abundance of prey lacking natural predators.
Following the reintroduction of Guam rails at Andersen Air Force Base in 2006, feral cats killed all of the introduced birds within eight weeks. Zoologist Bob Beck, a wildlife supervisor with the Guam Department of Agriculture's Division of Aquatic and Wildlife Resources, is credited with leading the efforts to capture the remaining wild Guam rails, Guam kingfishers, and other native birds to save them from extinction.
Guam rail is Critically Endangered on this catalog because that is the IUCN category stored on Wikidata. Confirm the official criteria and any later count on iucnredlist.org.
Sources
Written for this catalog from the English Wikipedia article on Guam rail, Wikidata item Q28070788 and GBIF occurrence geography. Family and order context is original field-guide writing about the group, not a copied assessment of this one species. Wikipedia text is CC BY-SA. Not an IUCN assessment. Counts, when quoted, can change — confirm them on the recovery programme and on iucnredlist.org.
