The ‘Anianiau is the smallest extant native Hawaiian bird. Constantly on the move, males are easily recognized by their bright yellow plumage and lively song. Females are slightly duller and can be distinguished by their small size and evenly yellowish green color. This Hawaiian honeycreeper was originally found throughout Kaua‘i Island but is now confined to mountain forests, where it is among the most widespread native forest birds on Kaua‘i.
First collected by the noted American naturalist J. K. Townsend in the mid-1830s (Olson and James 1994a), the ‘Anianiau was not described for another 50 years (Stejneger 1887). Although its nest was first found in 1900 (Bryan and Seale 1901), little attention was paid to this species until the late 1960s, when C. R. Eddinger began research on the breeding biology of the ‘Anianiau and three other common Hawaiian honeycreepers on Kaua‘i. As a result, the ‘Anianiau's breeding behavior is comparatively well known. Eddinger's work still provides most of what is known about this active sprite.
An insect gleaner and nectar feeder, the ‘Anianiau is found in a variety of habitats, from dry valleys in the northwest of the island to the depths of the Alaka‘i wilderness, one of the wettest spots on Earth. Able to tolerate considerable habitat disturbance, the ‘Anianiau inhabits upland forests dominated by alien plants, but it is most common in undisturbed native forests. Despite the destructive effects of 2 major hurricanes in the past 15 years, populations appear stable. No recent population estimates of this species are available, but it seems to be holding its own, at least in accessible locales visited by birders and biologists.