The O‘ahu ‘elepaio is a small, adaptable monarch flycatcher endemic to the island of O‘ahu. Males and females are dark brown above and white below with variable light brown streaks on breast and conspicuous white wing bars, tail feather tips, and throat. Both sexes have variable amounts of blacking markings, but males tend to have more. The bird’s name is derived from its primary song which is a shrill whistle given only by males. Unlike Hawaiian honeycreepers, both males and females participate almost equally in all aspects of rearing. Finely woven cup nests are built in a variety of native and non-native trees.