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

Description 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.

Hawaiian duck - Photo credit © Hob Osterlund

Population

The koloa is endemic and, prior to 1900, common on all the main Hawaiian islands except Lāna‘i and Kaho‘olawe. People first noticed them to be rare around 1915. Today, Kaua‘i and Ni‘ihau are likely the only islands to support a viable population of pure Koloa and Hanalei and Hulē‘ia NWRs support the highest numbers of koloa on Kaua‘i.

The primary cause for the historical decline in numbers is loss of wetland habitat and over-hunting. Other factors include predation by introduced animals (e.g., rats, dogs, cats), disease, and environmental contamination. Currently, the biggest threat to koloa is hybridization or crossbreeding with introduced/feral mallards.

Habitat

Koloa can be found in lowland wetlands, river valleys, mountain streams, and bogs.

Feeding Habits

Koloa eat mollusks, crustaceans, insects, and aquatic plants.

Breeding

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, pig, and dog attacks. The chicks are sometimes eaten by bullfrogs and bass.

Saving Hawai‘i's Native Duck
Hawai‘i Conservation Alliance has released a position paper about the threat that feral mallards pose to Koloa maoli, Hawai‘i’s native duck. To download the paper and find out more about what can be done to help recover koloa, please visit their website.

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