Guam Rail

(Gallirallus owstoni)




Facts about this animal

Resembling a grouse, this medium-sized rail is about 28 cm long and weighs 170 - 300 g. The plumage is dark brown and it has white stripes on its stomach. It's a flightless bird, but can flutter about 1 to 3 meters at a time! Rails live in pairs and breed throughout the year. They build shallow cups on the ground for nests for their three or four eggs, which they incubate for 19 days. Maturity is reached at the age of 4 months. They are omnivorous, eating leaves, seeds, fruits, small lizards, bird eggs, small mammals, and carrion.

Due to predation by the invasive brown tree snake (Boiga irregularis) the Guam rail was extirpated from the wild in the early 1980’s. It survived only in captive-breeding facilities in Guam and in 14 zoos in the USA.

In the 1980s, several zoos and government agencies corralled the last few Guam rails to start a zoo breeding programme. Guam rails breed well in zoos, and the current world zoo population is about 200. In 1989 attempts to establish an experimental population of rails on Guam’s neighbouring snake-free island of Rota (Northern Mariana Islands) were initiated. Between December 1989 and August 1999, 267 captive-reared rails were released while evaluating the success of different release methods. Reproduction by ex aitu-reared rails on Rota was first documented in 1995. During the summer of 1999, at least three pairs of captive reared Guam rails successfully produced 5 nests with eggs and hatchlings. Rails are also now being released into the wild on an Air Force Base area in northern Guam where brown tree snakes are being actively controlled. In November 1998 16 captive-reared Guam rails were released into this area. By late December 1998 a first nest was discoverd. Although not all of the released rails survived, no losses could be attributed to predation by snakes or other predators. By October 1999, 9 rails made at least 16 nesting attempts, yielding 46 eggs. Apparently all but six of the eggs hatched.

Did you know?
that the Guam rail came to the Guam Island thousands of years ago and was able to fly at that time? However, since there were no predators on Guam, it slowly lost the ability to fly.


Class AVES
Suborder GRUES
Name (Scientific) Gallirallus owstoni
Name (English) Guam Rail
Name (French) Râle de Guam
Name (German) Guamralle
Name (Spanish) Râle de Guam
Local names Guam.: ko'ko'
CITES Status Not listed
CMS Status Not listed



Photo Copyright by
Guy Dutson



Range Guam (Reintroduced), Northern Mariana Islands (Introduced)
Habitat Forest, savanna, scrub, secondary grassland, fern thickets and agricultural areas, but not in freshwater wetland habitats.
Wild population This species was extinct in the wild, but there's a reintroduction program on Guam and several specimens were introduced to Rota Island. Number of surviving animals and there offspring is not known.
Zoo population None reported to ISIS (2008), but currently 14 zoological institutions in the US keep this species and participate in the Guam Rail Species Survival Plan.

In the Zoo

Guam Rail


How this animal should be transported

For air transport, Container Note 11G of the IATA Live Animals Regulations should be followed.


Find this animal on ZooLex


Photo Copyright by
Guy Dutson

Why do zoos keep this animal

The role of the zoos is to implement captive breeding programs under the Species Survival Plan (SSP) that aim to preserve the genetic diversity of the Guam rail. Another goal of the breeding program is also to produce young rails for the reintroduction program, while maintaining a population of 150 to 175 birds in zoos for reproduction in the breeding program.