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
Leaf nearly petiolate or have an extremely short petiole and may appear to be sessile. In clasping or decurrent leaves, the blade partially surrounds the stem. When the leaf base completely surrounds the stem, the leaves are said to be perfoliate, such as in "Eupatorium perfoliatum". In peltate leaves, the petiole attaches to the blade inside the blade margin. In some "Acacia" species, such as the koa tree ("Acacia koa"), the petioles are expanded or broadened and function like leaf blades; these are called phyllodes. There may or may not be normal pinnate leaves at the tip of the phyllode. A