Kauai 'Akialoa

Hemignathus procerus

Description

The Kauai 'akialoa (Hemignathus procerus ) male and female differ dramatically in coloring. The adult male is characterized by shades of olive. The head is a dark ashy-olive that shades into olive on the back and then becomes brighter on the rump. Its underside is sulphur-yellow, with light primrose on the abdomen; the flanks appear washed in olive, and the undertail converts to an olive-yellow color, with wing-and tail-quills ashy-brown edged outwardly with olive. The black bill is 2.2-2.6 in (5.6-6.6 cm) in length; the feet are bluish-black. The respective body and tail lengths are about 7.4-19.8 in (18.8-50.3 cm), with the maxilla following the curve about 1.1 in (2.8 cm) in length. Adult females are characterized by a dingy yellow-buff, with the feathers on the head a yellowish-olive with black centers. The underside is an olive buff. Maxilla follows the curve.

Behavior

The nest, eggs, and young of the Kauai 'akialoa have never been found. Females dissected in April had enlarged ovaries, which with their singing and chasing at that time denoted breeding season. A female collected July 20, 1960, was apparently in post-breeding condition. Incubation is probably about two weeks. Nothing is known of the parental care, though the young are believed to be altricial (helpless and naked at birth).

The Kauai 'akialoa is nonmigratory but may move in relation to food supply. Evidence suggests that most of Hawaii's endemic land birds do not move more than a mile or two (2-3 km) from the nest in which they hatched. Some species do wander up, down, and around the mountain slopes at different times of the year. This species does not fly about in flocks but keeps singly or in pairs; it is sometimes seen in company with 'amakihi and 'akikiki (Kauai creeper).

The Kauai 'akialoa prefers the nectar of some kinds of arborescent Lobeliaceae, plants called haha and aha-wai by the natives, especially those with large corollas. They were known to feed on the 'ohi'a flower nectar, spiders, geometrid caterpillars, wood-and bark-eating gelechiid larvae, mature beetles of Carabidae, small metallic weevils of the genus Oodemas, Anobiidae, larvae of the latter and of Cossonidae, small cockroaches, and the remarkable crickets (Prognathogryllides ) that are peculiar to the islands. They are probably still largely nectar-eaters, although possibly on the way to becoming entirely insectivorous. The insects on which the Kauai 'akialoa feeds are sought in or beneath the bark of trees, especially the large koa trees. The species could be traced by its audible tapping on the bark, the sound resembling that produced by the strokes of the beak of the nukupu'u, except that it was not as loud.

The Kauai 'akialoa occasionally descends to the ground to forage for grubs and insects among the dead leaves and possibly to pick up gizzard stones. It searches the bases of the leaves of the i'ei'e (Freycinetia ) and halapepe (Dracaena ).

The species is probably diurnal.

Individual members of the species answer each other with a chirp; they also have a distinct call much like a linnet's, although slightly louder. Both male and female have a light sweet song, the female with fewer notes than the male. In January and February of 1891, their singing was not heard, but in March and April it was quite noticeable, and they also seemed to have a different chirp in April, evidently a breeding season.

Habitat

During the 1890s, the species occurred in all forests of Kauai from a few hundred feet in elevation to the highest elevations of the upper rain forest, presumably being most abundant in the mesic koa forests (elevation 2,500-3,500 ft [762-1,066.8 m]) around Kaholuamanu in the south-central mountains. Its range at that time must have included the very wet 'ohi'a rain forest at 4,000-5,000 ft (1,219.2-1,524 m) and extended into the lowland kukui forest and lowland introduced vegetation. The only four positive reports of the Kauai 'akialoa in the twentieth century were on the upper plateau between Kaholuamanu on the south to the upper Koaie Valley, the former at an elevation of 3,600 ft (1,097.3 m) in an area of mixed koa and 'ohi'a trees and the latter at an elevation of about 4,000 ft (1,219.2 m) in an area of 'ohi'a trees.

The Kauai 'akialoa's very limited range at the end of the twentieth century apparently included only a portion of the Alakai Swamp. Numerous meandering mountain streams dissect the area so that except for major ridges, which occasionally broaden into relatively flat areas and bogs, the land is a maze of narrow knifelike ridges, cliffs, ledges, and steep inclines to adjoining streams. The predominant 'ohi'a canopy ranges from 46-66 ft (14-20.1 m) with ranges from 60-90%, and the understory is composed of dense native shrubs.

Distribution

The Kauai 'akialoa, from the time of its discovery around 1887 until the beginning of its decline by the end of the nineteenth century, occurred in varying numbers throughout the forests of Kauai, from the lower elevations to the mountain tops. The species was last collected just south of the Koaie Valley in 1960 and last reported seen March 1965 in the same area, although there was a secondhand report of a possible sighting in 1968 or 1969 in an undesignated location, one probably near the same area as the earlier sightings.

It is possible that the Kauai 'akialoa still exists in limited numbers in the Alakai Swamp and the forests immediately south of the swamp. The species was not seen during surveys of the avifauna of Kauai from 1967 to 1984.

Threats

Threats to the Kauai 'akialoa are probably predation and disease. This species has only been seen four to six times in the twentieth century, has not been collected since 1960, and has not be seen since 1965; extinction is a very real possibility. It was not found from 1967 to 1984, and it was not seen during intensive multiple-person surveys in 1981 and 1985. However, many decades passed between sighting of the Kauai 'akialoa and other rare Hawaiian birds, and there is a possibility that a few still exist in some remote portion of the Alakai Swamp.

Conservation and Recovery

Little is known about the reasons for forest bird decline throughout the Hawaiian Islands, especially on Kauai. Although severe forest bird decline occurred on many of the islands during the nineteenth century, primarily because of deforestation, the most drastic decline on Kauai occurred during the first 30 years of the twentieth century.

Many acres of forest have been cleared for agriculture and pasture. Grazing animals have been introduced, and some types have adapted to the wild. Alien plants, insects, and diseases have spread aggressively. In addition to competition with exotic species, the 'akialoa must also compete with other native birds and contend with rats and other introduced predators. Natural variations in food supply and the dramatic seasonal variation in the 'ohi'a blossoms also affect the 'akialoa.

In 1964, 4,023 hectares (9,940 acres) of the Alakai Swamp were set aside to establish the Alakai Wilderness Preserve. The U. S. Fish and Wildlife Service (FWS) Recovery Plan has identified an area of about 7,890 hectares (19,500 acres) that is considered essential for the survival of forest birds on Kauai. Most of this area is currently under control of the Hawaii Division of Forestry and Wildlife.

In its recovery plan for Kauai forest birds, which includes the Kauai 'akialoa, the FWS notes the imminent danger of extinction for many Hawaiian native birds. It recommends establishment of a captive propagation program and sperm bank as a last-ditch attempt to save as many as possible. For the Kauai 'akialoa, such efforts may have come too late.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N.E. 11th Ave.
Portland, Oregon 97232-4181
(503) 231-6121
http://pacific.fws.gov/

Pacific Remote Islands Ecological Services Field Office
300 Ala Moana Blvd., Room 3-122
P. O. Box 50088
Honolulu, Hawaii 96850
Telephone: (808) 541-1201
Fax: (808) 541-1216

References

Berger, A. J. 1891. Hawaiian Birdlife. University of Hawaii Press, Honolulu.

Huber, L. N. 1966. "Observation of Akialoa, Field Notes. Alakai Swamp, Kauai, March 1965." Elepaio 26 (8): 71.

Scott, J. M., et al. 1988. "Conservation of Hawaii's Vanishing Avifauna." Bioscience 38 (4): 238-253.

U. S. Fish and Wildlife Service. 1983. Kauai Forest Birds Recovery Plan. U. S. Fish and Wildlife Service, Portland.