A small, brightly colored, restless honeycreeper of montane Hawaiian rain forests, the ‘Akepa is unusual in morphology, plumage, and behavior. Perhaps its most noteworthy character is a lateral asymmetry of the bill: the lower mandible is curved to one side, an extremely rare trait in birds. The ‘Akepa uses this unusual bill to pry open leaf and flower buds in search of arthropod prey in a manner similar to that of crossbills (Loxia spp.) opening conifer cones.
Another interesting feature of this species is that males exhibit delayed plumage maturation and do not acquire Definitive (adult) plumage until after their second breeding season. Such a long delay in plumage maturation is unusual for a 10- to 12-g bird.
The nonterritorial ‘Akepa has low annual reproductive output, high annual survivorship, and large group displays by males that are reminiscent of leks, even though the ‘Akepa is socially monogamous, with long-term pair bonds and biparental care. The only close relative of the ‘Akepa is the ‘Akeke‘e (Loxops caeruleirostris ) of Kaua‘i Island; the two species were considered one species between 1950 and 1991 because of their similar bill morphology, despite marked differences in appearance, voice, and breeding biology.
Although first collected by naturalists of the James Cook expedition in 1779 and formally described just 10 years later, the ‘Akepa, like most other Hawaiian birds, languished in relative obscurity for the next two centuries. Widely collected in the 1800s, it was only rarely noted in the twentieth century and was not studied by biologists until after being listed as an Endangered Species by the U.S. Fish and Wildlife Service. Large-scale surveys in the late 1970s and early 1980s revealed larger populations of the Hawai‘i Island subspecies than were previously known, but confirmed the near extinction of the Maui Island subspecies. The O‘ahu Island subspecies has been considered extinct for more than 50 years. Despite a relatively robust population on Hawai‘i, the first nest was discovered only in 1974, and almost nothing was known of the life history of the ‘Akepa until the late 1980s. Core populations of the Hawai‘i ‘Akepa seem stable, but peripheral populations appear to be declining, and the Maui ‘Akepa is in critical danger of imminent extinction, if not already extinct.
Because of the extreme rarity of this species on Maui and its extinction on O‘ahu, all information presented here is for the Hawai‘i Island subspecies, unless otherwise noted. Most data are from studies by JKL and LAF at Hakalau Forest National Wildlife Refuge (NWR).