Endangered Species in the Pacific Islands

Guam Rail / Gallirallus owstoni  / Ko‘ko‘

	The Guam rail has a brown head, neck and eye stripe; near gray throat and upper breast; short wings that are dark with brownish spots and barred with white; lower breast, abdomen, under tail coverts, and tail are blackish with white barrings; gray bill, long legs and dark brown feet; and red iris. Females are similar but slightly smaller than male.
Guam rail - Photo credit Suzanne Medina/Guam Department of Agriculture

Habitat & Behavior: The Guam rail is a secretive, flightless, territorial species that is most easily observed as it bathes or feeds along roadsides or field edges. The call is a loud, piercing whistle or series of whistles, usually given by two or more birds in response to a loud noise, the call of another rail, or other disturbances. Though individuals will respond almost invariably to the call of another rail, the species is generally silent.

The rail is one of the few native birds of Guam that is found more frequently in scrubby second growth or mixed forest than in uniform tracts of mature forest, and might have been more abundant after the arrival of man than before.

It is an omnivorous feeder but appears to prefer animal over vegetable food. It is known to eat gastropods, skinks, geckos, insects, and carrion as well as seeds and palm leaves.

The rail is a year-round ground nester making it highly susceptible to predators, such as the monitor lizard and the rat. It lays 2-4 four eggs and both parents share in the construction of a shallow nest of leaves and grass. A far more efficient predator was introduced in the 1950s, the brown treesnake. The snake is generally considered to be the primary cause of the disappearance of most of Guam's native birds.

Past & Present:
Before the 1970s, the Guam rail occurred island-wide and distributed in all habitats except wetlands. The population declined severely from 1969-1973, and the rail disappeared from southern Guam in the mid 1970s. The decline of the rail continued until in 1980, only 10 rails were recorded. In a desperate move, 21 birds were caught in the wild in the mid-1980s and placed in captive breeding both in the continental United States and on Guam.