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This Hawaiian honeycreeper was only discovered in the rainforest of Maui's Haleakala Volcano in 1973, and yet it probably holds the distinction of being the most endangered bird in the world. Despite habitat preservation and restoration efforts over the past 25 years, this species is likely extinct.
Po'o-ulis are chunky, medium-sized Hawaiian honeycreepers, a group of relatively small, finch-like songbirds found only in the Hawaiian Islands. They are identified from all other honeycreepers by their combination of a black facial mask (the Hawaiian name Po'o-uli means "black-faced"), a whitish cheek-patch and throat, brown upperparts, and a very short tail. Adult males are creamy white below, while females have grayish underparts.
Po'o-ulis are now found only in Hawaii's Hanawi Natural Area Reserve, on the northeast slope of Maui's Haleakala Volcano. When this species was discovered in 1973, it was estimated that there were a few hundred individuals. In 1980, the Po'o-uli population was estimated at 140 birds. By the mid-1990s, survey teams were having a difficult time finding any Po'o-ulis. In 2002 is was believed that only three Po'o-ulis remained in existence.
The few remaining Po'o-uli individuals were found in windswept, high-elevation rainforest on the northeast slope of Haleakala Volcano. Although the species was restricted to extremely wet, high-elevation forest, fossil records suggest that Po'o-ulis were once found in dry forest at lower elevations on the southwestern slope of Haleakala.
When they were more numerous, Po'o-ulis were observed as single individuals, pairs, family groups, and in mixed-species flocks with other honeycreepers. Po'o-ulis forage by working along a tree limb, searching for food items in bark and epiphytes. Members of this species consume large quantities of land snails, making these birds unique among the Hawaiian honeycreepers. Po'o-ulis also feed on arthropods and fruit.
This species is now on the verge of extinction, with an apparent population of just three individuals. The greatest immediate threat to Po'o-uli, then, is the death of these individuals before they can reproduce. Two of these birds are females, and one male, so there is still hope for successful breeding among the few remaining individuals. Unfortunately, though, these three birds are all located in different parts of the Hanawi Natural Area Reserve, and have not come into contact with each other naturally.
The exact causes of Po'o-uli's rapid population decline since the species' discovery in 1973 are not well understood at all. Small introduced mammals, including cats, two species of rat, and mongoose, are believed to prey upon nests and adults, although this suspicion has not been documented. In addition, all of these potential predators have been present on Maui since at least the late 1800s, so Po'o-ulis have been sharing their rainforest habitat on Haleakala with these mammals for over 100 years. Introduced rats are also suspected of depleting the supply of arthropods and mollusks where Po'o-ulis are found, but this has not been documented, and native snails remain common in Po'oulis' very limited range. The activities of feral pigs on the Hawaiian Islands have had a devastating impact on the native flora of the region, which in turn has had serious implications for the many unique Hawaiian bird species that evolved together with these plants. In Po'o-uli's current rainforest habitat, feral pigs have wiped out the forest understory in spots; this leads to erosion and disturbance of roots, which results in the death of subcanopy trees.
The most recent conservation effort on behalf of Po'o-ulis took place in April 2002, when scientists captured one of the two remaining females and transported her to the territory of the one remaining male (http://news.fws.gov/newsreleases/r1/7CC1AE71-040D-4045-B2C8CC1A4058978E.html). The hope of this effort was that the female would remain in the male's territory and the two birds would eventually form a wild breeding pair. Unfortunately, the female did not stay in the male's territory, instead returning to her own home range after a few hours. Scientists were encouraged, though, by the female's ability to remain calm and even feed while she was in captivity. This leaves open the possibility of a captive breeding program, an idea that has previously met with some resistance for fear that Po'o-ulis would not fare well in captivity.
Po'o-uli was listed as an Endangered Species by the U.S. Fish and Wildlife Service in 1975. Conservation efforts in the past have concentrated on habitat protection and restoration. In 1986, Hawaii established the Hanawi Natural Area Reserve to protect native ecosystems that support populations of Po'o-ulis and other endangered Hawaiian birds. The state government has also pursued a fencing and control program to exclude feral pigs from areas in the Hanawi Natural Area Reserve. Where fences have been erected and pigs eliminated, native understory plants have quickly recovered, setting the stage for the regrowth of subcanopy trees and the return of a healthy, native rainforest ecosystem.
What Can You Do?
The Endangered Species Act has helped in the attempt to protect Po'o-ulis, and has made it possible to learn critical information about their biology. Audubon continues to work to ensure that this vital legislation is being used to protect our publicly-owned wildlife resources. Check out http://www.audubon.org/campaign/ to learn of the latest news about the Endangered Species Act and how you can help. To learn more about other species protected under this legislation, visit: http://endangered.fws.gov/
BirdLife International (2006) Species factsheet: Melamprosops phaeosoma, Po'o-uli http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=8926&m=0
Pratt, H.D., P. L. Bruner, and D. G Berrett. 1987. The Birds of Hawaii and the Tropical Pacific. Princeton University Press, Princeton.
Pratt, T.K., C.B. Kepler, and T.L.C. Casey. 1997. Po'ouli (Melamprosops phaeosoma). In The Birds of North America, No. 272 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D. C.