Pacific Islands Fish and Wildlife Office
Pacific Region

Endangered Species in the Pacific Islands

Hawaiian Duck / Anas wyvilliana  / Koloa maoli (native duck)

Photo of 2 koloa The koloa, is generally mottled brown and has a green to blue speculum (the distinctive feathers on the secondary wing feathers) with white borders. Adult males tend to have a darker head and neck feathers (sometimes green). Both sexes have orange legs and feet. Females have a dull orange bill. The male koloa is 19 to 20 inches in length while the female is 16 to 17 inches. Their quack is a little softer than the mallard and koloa are not as vocal.
Koloa - Photo credit Hob Osterlund

Habitat & Behavior:
Koloa can be found in lowland wetlands, river valleys, and mountain streams. They are cautious ducks that travel in pairs. Koloa eat mollusks, insects, and freshwater vegetation. They can begin breeding at one year old and nest year-round, but the main breeding season is between January and May. Two to ten eggs are laid in a well concealed nest lined with down and feathers. The incubation period is 30 days. Because their nests are established on the ground, they are highly vulnerable to mongoose, cat, pig, and dog attacks. The chicks are sometimes eaten by bullfrogs and bass.

The largest number of pure koloa can be found on the island of Kaua‘i.

Past & Present:
Koloa is endemic and used to be found on all the main Hawaiian islands except Lana‘i and Kaho‘olawe. People first noticed them to be rare around 1915. A koloa restoration program was initiated in 1962 by the World Wildlife Fund and the state through the Federal Aid to Wildlife Restoration Act. By 1979, 350 koloa had been released on O‘ahu and Hawai‘i as part of this program. In 2002, biologists estimated the populations to be 2,000 koloa on Kaua‘i-Ni‘ihau, 300 on O‘ahu, 25 on Maui, and 200 on the Big Island.

The primary cause for the historical decline in numbers is loss and degradation of wetland habitat, predation by introduced animals (e.g., rats, dogs, cats), and hunting. Invasion of wetlands by alien plants, disease, and sometimes environmental contamination. Today, hybridization (mating with feral mallards) is the biggest threat to the species.

Conservation Efforts:
State and Federal efforts in protecting wetlands, enforcing strict hunting laws, educating, and working with private organizations and landowners play an important role in ensuring the livelihood of the koloa and many other waterbirds.

The koloa was listed as an endangered species in 1967 under the Federal Endangered Species Act. The Hawaiian Waterbirds Recovery Plan was completed in 1978, revised in 1985, and is currently being revised and updated again.

Mālama Hawai‘i is assisting biologists and resource managers in educating the public about the Koloa Maoli and threats to its survival. Visit the website at the following link -


Last updated: September 20, 2012
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