American Bird, the Hawaiian Crow, Now Extinct in the Wild
HONOLULU, Hawaii, December 18, 2003 (ENS) - A crow found in Hawaii and nowhere else in the world is believed to be extinct in the wild. Known locally as the 'alala, the Hawaiian crow, Corvus hawaiiensis, was once widespread on the island of Hawaii, but now survives only in captivity.
Currently, there are 40 'alala, representing the entire known population of the species, in captivity at the Keauhou Bird Conservation Center on the Big Island of Hawaii and at the Maui Bird Conservation Center.
The U.S. Fish and Wildlife Service today published a draft revised recovery plan to breed the species back from the 40 birds in captivity and eventually release them into the wild.
Hawaii has been steadily losing its biological diversity. More native species have been eliminated in Hawaii than anywhere else in the United States and most places in the world.
Until the 1990s a few wild 'alala lived on the southwest slopes of Mauna Loa Volcano on the island of Hawaii in an area that is now part of Hakalau Forest National Wildlife Refuge.
The wild 'alala population dwindled from 11 birds in 1992 to three birds in 2000. Jeff Burgett, a biologist with the U.S. Fish and Wildlife Service who made the last known sighting of wild 'alala on June 14, 2002, is still unwilling to label the species extinct in the wild. He believes one or two birds may remain, but not another pair that could breed in the wild.
To bring the species back, the draft revised recovery plan proposes to build the captive population, restore the bird's degraded habitat, and then release 'alala gradually into the restored ecosystem.
The cost to cover activities outlined for the first five years of the plan is $11.8 million. Continued intensive management will be required for several decades at similar or increased cost for successive five year management periods, the plan predicts.
The omnivorous, forest dwelling crow originally inhabited the dry and moist mesic forests on the island of Hawaii. Although 'alala were still abundant in the 1890s, their numbers decreased throughout the 20th century despite legal protection conferred by the Territory of Hawaii in 1931, the U.S. Endangered Species Act in 1973, and the State of Hawaii Endangered Species Act in 1982.
Destruction of most of the lowland forests restricted the crow's ability to follow seasonal fruiting up and down the mountains, the Fish and Wildlife Service explains. The upland forests have been thinned and fragmented, and many fruiting plants lost, due to logging, ranching, and the effects of grazing by feral pigs, cattle, and sheep. Mongooses, cats, and rats prey on 'alala eggs and fledglings.
Diseases carried by introduced mosquitoes may have caused the mortality of many 'alala, as they did other forest birds. The crows also suffered from avian malaria, avian pox and toxoplasma, a disease carried by feral cats and transmitted to birds through cat droppings.
Scientists also believe that the 'alala's natural enemy, the Hawaiian hawk, has killed many of the rare crows, especially in areas where ungulate grazing has reduced understory cover.
In the 1990s a program to remove eggs from wild 'alala nests and raise the chicks in captivity was accomplished by workers from the Peregrine Fund under contract to the Fish and Wild Service.
Sixteen birds from that program were released into the wild, but the hawks killed five, and the rest died from other causes. Releases were halted in 1999 because experts feared too many deaths would deplete the bird's genetic diversity.
The number of birds gradually declined to a single pair in 2002. The 'alala survives today only because a captive flock has been established and maintained; it would otherwise be extinct, and the Service says, "This is the first Hawaiian forest bird whose extinction has been prevented by captive propagation."
But the captive flock of 40 represents the progeny of only nine founding individuals, an extremely small sample of the species’ original gene pool.
Significant features of the species’ life history, behavior, ecological interactions, and habitat needs remain unknown, the Service says in its draft recovery plan. As a result, detailed long term recovery planning is difficult, and the exact needs of the recovery program cannot be specified beyond a relatively short time horizon.
Recovery of this species will require both sustained, long term conservation actions and repeated experimentation to determine the optimal means to reestablish wild populations, the draft recovery plan states.
It now appears that the habitat at the site used for the releases from 1993 to 1998, as well as throughout the historical range of the species, requires restoration in order to support an 'alala population, so a major shift in thinking about recovery has taken place, from release into the wild to increasing the population size in captivity.
But, the Service says, the 'alala is difficult to breed in captivity, requires expert husbandry and separate aviaries for each pair, and has a relatively low rate of successful reproduction.
The second strategic imperative for 'alala recovery is restoration of native forests to the point that released crows can survive and reproduce. But ecosystem recovery is a slow process, so restoration of sites that will be used for 'alala recovery must begin at once, the Service says. "Otherwise the program risks producing birds for which no suitable habitat exists."
The Fish and Wildlife Service is aware that the 'alala is a symbol of Hawaii’s natural heritage and is associated with a style of chanting that takes its rhythm from the bird's call.
The Service will rely on public support to bring the 'alala back to its natural habitat. Raising the funds necessary for the captive program and habitat restoration, acceptance of ungulate and predator management in natural areas, and cooperation by private landowners all depend on broad public understanding of the program’s goals, the agency says.
The original recovery plan for the 'alala was published in 1982. The draft plan released today is intended to update the original plan. Comments on the draft revised recovery plan must be received by February 17, 2004 to receive consideration.
The Service intends to prepare and publish new implementation plans as addenda to the revised recovery plan every three to five years as experts gain further knowledge of the 'alala and are better able to determine techniques for the effective recovery of this species in the wild.
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