Habitat loss due to land use changes and introduction of invasive plants, as well as hunting by humans and by invasive animals such as rats and mongoose, have threatened native waterbird populations. All of Hawaii's endemic rails, flightless geese, and one type of ibis have become extinct. All six surviving species of endemic waterbirds are endangered, with populations of less than 3,000. Of these, all but the Laysan duck and Nene are found in Hamakua.
Nearly 60 species of migratory ducks, geese and shorebirds have used the Hawaiian Islands during the winter. These waterbirds have also shown a marked decline, from tens of thousands in the 1950s to only a few thousand in the 1990s.
The 'Alae 'Ula (Hawaiian moorhen) is called "burnt forehead" because its red frontal shield is said to have been burnt when it brought fire to the Hawaiian people. Found only on Oahu and Kauai, this bird is the most rare. It nests in the dense floating vegetation.
The Koloa Maoli (Hawaiian duck) were eliminated everywhere except the Big Island. 326 captive ducks were reintroduced to Oahu from 1958 - 1982. All koloa have white and brown mottled coloring, similar to female mallards. The male mallards mate with the female koloa, creating a population of hybrids. They nest in dense vegetation by the water.
The Ae'o (Hawaiian Stilt) is called "one standing high" due to the bird's long pink legs. It feeds and nests in the shallow water and mudflats.
The 'Auku' (Black-Crowned Night Heron) is indigenous, meaning it is also found in other parts of the world. Unlike the other subspecies which are active mostly at night, the subspecies in Hawaii hunts during the day. It is not endangered.
'Alae Ke'o Ke'o
The 'Alae Ke'o Ke'o (Hawaiian coot) is secretive and builds floating nests that are anchored to stationary vegetation. These birds have big feet with flaps that extend on either side of their toes to help them swim. They like open water and dive for submerged plants.