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
Metrosideros polymorpha the most common native tree in the Hawaiian Islands, tolerating a wide range of soil conditions, temperature, and rainfall. It grows from sea level right up to the tree line at elevations of and is commonly found in moist and dry forests, high shrublands, and is a colonizer of recent lava flows. It is relatively slow growing. Dominant in cloud forests above , the tree is also common in seasonally wet forests, where it may be dominant or form mixtures with the native "Acacia koa". "Metrosideros polymorpha" may occur as a tall tree or a prostrate shrub, and everything in