Wary by nature, especially when nesting or molting, the Hawaiian duck often occurs alone or in pairs (7). It is a strong, agile flier and is believed to make daily and seasonal altitudinal movements. Although inter-island movements are unknown, patterns in abundance suggest this species does move between the islands in response to rainfall and food availability (4) (8). The Hawaiian duck is an opportunistic feeder, foraging mainly in shallow water, where it takes aquatic insects, molluscs, crustaceans, seeds and other plant matter (2) (4) (6).
The reproductive ecology of this duck is poorly known (6), but breeding has been documented year-round with a peak between December and May on Kauai, and March and June on Hawaii (2) (3). The female normally builds a nest away from human disturbance, in herbaceous upland vegetation near a wetland or stream, and lays up to ten eggs (4) (6). Following an incubation period of around 30 days, the precocial chicks hatch and trail their mother to the safety of water (3).