Most of these species became extinct by habitat loss, the introduction of mammalian predators (like rats, pigs, and mongooses), and by extensive hunting (their plumage was used for the creation of precious ʻaʻahu aliʻi (robes) and ʻahu ʻula (capes) for aliʻi (Hawaiian nobility).

[4][5] The Kauaʻi ʻōʻō was the last species of this genus to become extinct, likely a victim of avian malaria.

[6] Until recently, the birds in this genus were thought to belong to the family Meliphagidae (honeyeaters) because they looked and acted so similar to members of that family, including many morphological details.

A 2008 study argued, on the basis of a phylogenetic analysis of DNA from museum specimens, that the genera Moho and Chaetoptila do not belong to the Meliphagidae but instead belong to a group that includes the waxwings and the palmchat; they appear especially close to the silky-flycatchers.

[7] The album O'o by jazz composer John Zorn, released in 2009, is named after these birds.