Hawaiian Duck / Anas wyvilliana / Koloa maoli (native duck)
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.
Koloa can be found in lowland wetlands, river valleys, mountain streams, and bogs.
Koloa eat mollusks, crustaceans, insects, and aquatic plants.
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