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
Mauna Kea State Recreation Area. A band of ranch land on Mauna Kea's lower slopes was formerly "Acacia koa" – "Metrosideros polymorpha" (koa-ōhia) forest. Its destruction was driven by an influx of European and American settlers in the early 19th century, as extensive logging during the 1830s provided lumber for new homes. Vast swathes of the forest were burned and cleared for sugarcane plantations. Most of the houses on the island were built of koa, and those parts of the forest that survived became a source for firewood to power boilers on the sugarcane plantations and to heat homes. The once vast