Hawaiian Crow

Corvus hawaiiensis

Description

The Hawaiian crow, Corvus hawaiiensis, is a large bird with a stocky body that measures 19 in (48.3 cm) in length; sooty brown, it appears almost black. This bird, known in Hawaiian as "alala," has a long and thick bill. This species of crow has also been classified as C. tropicus.

Behavior

The Hawaiian crow is more secretive than the common American crow and is usually heard before it is seen. Immature birds reach sexual maturity in their second or third year. Breeding pairs nest from March through July. Clutches consist of one to five eggs, but recently few young have survived to fledge.

Although omnivorous, the Hawaiian crow usually feeds on the fruits of trees and shrubs. It forages for insects among leaf litter and sometimes extracts nectar from flowers. Other foods include mice, small lizards, and the young of small birds.

Habitat

The Hawaiian crow is usually found in higher elevation ohia (Metrosideros collina ) or mixed ohia and koa (Acacia koa ) forests that have an understory of other native shrubs and plants; these produce fruit for the crow to eat. The Hawaiian crow prefers open forests or groves bordering pasture, avoiding the more densely grown and closed forests. Habitat elevation ranged originally from 1,000-8,000 ft (304.8-2,438.4 m). By the 1940s, the crow's range had become greatly reduced to a narrow, discontinuous belt at elevations between 2,500-6,000 ft (762-1,828.8 m).

Distribution

This species, known only from the island of Hawaii, had a historical breeding range restricted to the forested slopes of the Hualalai and Mauna Loa volcanoes. At the end of the nineteenth century, the Hawaiian crow occupied all of its known range and was considered abundant; since then the bird has declined so dramatically that fewer than 150 crows survived on the Big Island in the 1970s.

The outlook remains grim for the Hawaiian crow. Sometime in the early 1980s the species suffered a serious population crash. A 1986 estimate placed the number of Hawaiian crows in the wild at 12, and researchers were only able to locate two crows in the spring of 1987. By 1994, the species was making a slow turn-around, as the release of seven chicks from the hatching aviary expanded the wild population of "alala" by about 50%. Despite this significant increase, the 1994 wild population still stood at about 20 individuals.

Threats

No single reason for the drastic population decline of the Hawaiian crow has been determined, and prospects for its recovery are considered slim. Increased human settlement in the Kona districts and changes in land use have been cited as a cause. It is also clear that crows were widely hunted. The birds have been legally protected from hunting since 1931; however, the population did not rebound as anticipated.

Browsing and grazing by cattle, horses, sheep, and goats have caused significant changes in native forests; hoofed mammal activities may be a factor in the abandonment of some sections of the crow's range. Researchers were puzzled in the 1970s by the fact that crows inhabited some tracts of highly modified pastureland yet seemed absent from nearby, relatively pristine forests.

Generally low breeding productivity may have triggered the population crash in the 1980s. Studies during the late 1980s and early 1990s have determined that the average number of young fledged per nest is less than one. The causes of this reproductive failure seem to be a combination of poor hatchability of eggs, predation by rats or mongooses, avian diseases, and a declining food supply as many native food plants are crowded out by alien vegetation.

Conservation and Recovery

The state-run Olinda Endangered Species Propagation Facility on the island of Maui has finally turned the corner in captive breeding of the crows, although the difficulties of captive breeding are exacerbated by the low number of individuals and the very limited gene pool. Unfortunately, in June 1987, a fertile female died of egg-impaction. A fertile egg was hatched in early 1988, and the young crow fledged. This marked the breeding program's first unequivocal success.

On October 25, 1994, the first bird raised in captivity ventured outside the aviary and eventually was followed by the others. Upon their release, the chicks almost instantly began behaving like wild birds, foraging on native plants and searching for arthropods in tree bark. Four of the birds were produced at the Olinda facility, marking the first time that birds from the captive breeding flock were released into the wild.

Because of the differing views on appropriate management of "alala," the U. S. Fish and Wildlife Service (FWS) asked the National Research Council in 1991 to review the existing information and develop recommendations for recovering the species. Options considered ranged from bringing all the remaining birds into a captive-breeding program to leaving the wild population completely undisturbed. The National Research Council completed its work and filed its report in May 1992.

The information and recommendations contained in the report formed the basis for the Long-Term Management Plan for the "alala" prepared by the FWS and completed in 1993. This plan, reviewed and endorsed by the newly reinstituted recovery team, has served as the guideline for management during recent breeding seasons.

Contact

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

References

Baldwin, P. H. 1969. "The Alala (Corvus tropicus ) of Western Hawaiian Island." Elepaio 30(5): 41-45.

U.S. Fish and Wildlife Service. 1982. "Alala Recovery Plan." U.S. Fish and Wildlife Service, Portland.