Oʻahu nukupuʻu bill to pluck insects found underneath tree bark, the Oahu nukupuu fed on insects on flowering trees such as the koa ("Acacia koa") and ohia ("Metrosideros polymorpha"). These trees attract a large amount of insects due to their nectar-filled flowers. The Oahu nukupuu fed on koa in high elevation forests and fed on ohia in low elevations. The species was believed to have vanished as the spread of disease occurred, killing off nukupuu populations across the islands. In order to control the rat population in the sugar cane fields, mongooses were introduced to Hawaii and were suspected to be predators
Acacia koaia It can be seen on ranch land in North Kohala, and at a small fenced exclosure outside of Waimea known as the "koaia" sanctuary. "Koaia" is one of the species being used to revegetate the island of Kahoolawe, which lost most of its plant life to overgrazing and ordnance testing. Native Hawaiians ground "koaia" leaves and bark with "auaukoi" ("Senna occidentalis") and "kikānia pipili" ("Desmodium sandwicense") stalks. The mixture was then hydrated and used in a steam bath to treat diseased skin. The wood of "koaia" is harder and more dense than that of "koa". It was used to make