Koloa Maoli, Anas wyvilliana, are similar to and probably derived from the mallard. They are also known as Hawaiian ducks. Males grow to 19-20 inches, females 16-17 inches. Both sexes are generally mottled brown, resembling a small dark female mallard. The speculum (flight feathers) is green to blue, bordered on both sides by white. The adult male has darker head and neck feathers. The feet and legs of both sexes are orange. The bill is olive green in males, a dull orange or gray with a dark “saddle” in the female.
- The koloa maoli’s former range included all the Hawaiian islands except Lanai.
- Small, naturally breeding populations have been reestablished on Oahu and Hawaii through the release of birds reared in captivity.