Ko'ko' (Guam Rail)

Scientific Name: Rallus owstoni (Family RALLIDAE)

Common Name: Guam Rail

Chamorro Name: Ko’ko’

Audio sample of the Ko’ko’

Habitat and Natural History: The Ko’ko’ is a large rail, standing eleven to twelve inches or about twenty-eight centimeters tall. It lived in secondary forested areas mixed with grasslands and limestone forest, especially the edges near grassy areas. It nests year round laying one to four eggs in a nest of leaves and grass on the ground. The eggs are tended by both parents. Chicks can run after four days. Considered flightless, the ko’ko’ can only fly very short distances. It is an omnivorous feeder but seems to favor animals. It feeds on seeds and leaves as well as snails, lizards, insects and carrion.

Description: About twelve inches tall with long legs and large feet. The head, neck and eyestripe are brown. The short wings are spotted brown with white bars. The iris is red. The beak is grey.

Range: Guam, where it is endemic.

Current Status: Considered endangered by both the Government of Guam and the federal government. It has been extirpated from the wild and is held in captive breeding programs on Guam and the U.S. mainland. There has been an experimental population release on Rota, CNMI and in two locations on Guam. The Guam Rail was once abundant, commonly seen in backyards and agricultural fields. It was once hunted for food.

Threats: Habitat destruction and predation by the brown treesnake as well as feral cats, possibly pigs and monitor lizards.

By Gretchen R. Grimm, MS

Visit a Ko’ko’ on Guam
The Cushing Zoo
Tarza Water Park

Visit a Ko’ko’ in the United States
Cincinnati Zoo & Botanical Garden
Lincoln Park Zoo and the Guam rail
Racine Zoo and their Guam Rail Fact Sheet