Corvus hawaiiensis

Taxonomy

Assessment Information

Geographic Range

Habitat and Ecology

Threats

Conservation Actions

Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AVES	Passeriformes	Corvidae

Scientific Name:

Corvus hawaiiensis

Species Authority:

Peale, 1848

Common Name/s:

English

–

Hawaiian Crow

Assessment Information [top]

Red List Category & Criteria:

Extinct in the Wild ver 3.1

Year Assessed:

2008

Assessor/s

BirdLife International

Evaluator/s:

Butchart, S. & Taylor, J. (BirdLife International Red List Authority)

Justification:
The last two known wild individuals of this species disappeared in 2002, so the species is now classified as Extinct in the Wild. Some individuals remain in captive breeding facilities and a reintroduction plan is being developed.

History:

2004	–	Extinct in the Wild
2000	–	Critically Endangered
1994	–	Critically Endangered
1988	–	Threatened

Geographic Range [top]

Range Description:	Corvus hawaiiensis was distributed historically on Hawai`i in the Hawaiian Islands (USA), where the last individuals were found in and around the Kona Forest Unit of Hakalau Forest National Wildlife Refuge. Bones of this or a closely related species have been found on Maui, indicating a wider distribution before Western contact¹⁰. In 1992, there were only 11 or 12 birds in the wild^5,6, which had declined to three in October 1999⁶, and the last two individuals were last seen in June 2002: they did not return to their traditional nesting site in 2003 and have not been seen since. Nesting by the last known wild birds was probably confined to higher elevations on Mauna Loa in South Kona⁸. The last known wild chick fledged in 1992, and the last viable wild egg was laid in 1996⁸. The species persists in captive breeding facilities, with development of a reintroduction programme in progress⁷. Captive breeding started in the 1970s, but few fledglings were produced until eggs from wild nests were harvested and hatched in captivity during 1993-1996¹⁰. A total of 27 captive-reared juveniles, originating from eggs laid either in the wild or in captivity, were released during 1993-1999^10,12. By 1999, 21 released birds had died and the remaining six were captured to protect them and preserve genetic diversity^1,2,5,10. In 2006, the captive population stood at 53 individuals (38 at the Keauhou Bird Conservation Centre and 15 at the Maui Bird Conservation Centre), including 28 birds used as breeders⁸.
Countries:	Regionally extinct: United States

Range Description:

Corvus hawaiiensis was distributed historically on Hawai`i in the Hawaiian Islands (USA), where the last individuals were found in and around the Kona Forest Unit of Hakalau Forest National Wildlife Refuge. Bones of this or a closely related species have been found on Maui, indicating a wider distribution before Western contact¹⁰. In 1992, there were only 11 or 12 birds in the wild^5,6, which had declined to three in October 1999⁶, and the last two individuals were last seen in June 2002: they did not return to their traditional nesting site in 2003 and have not been seen since. Nesting by the last known wild birds was probably confined to higher elevations on Mauna Loa in South Kona⁸. The last known wild chick fledged in 1992, and the last viable wild egg was laid in 1996⁸. The species persists in captive breeding facilities, with development of a reintroduction programme in progress⁷. Captive breeding started in the 1970s, but few fledglings were produced until eggs from wild nests were harvested and hatched in captivity during 1993-1996¹⁰. A total of 27 captive-reared juveniles, originating from eggs laid either in the wild or in captivity, were released during 1993-1999^10,12. By 1999, 21 released birds had died and the remaining six were captured to protect them and preserve genetic diversity^1,2,5,10. In 2006, the captive population stood at 53 individuals (38 at the Keauhou Bird Conservation Centre and 15 at the Maui Bird Conservation Centre), including 28 birds used as breeders⁸.

Countries:

Regionally extinct:

United States

Habitat and Ecology [top]

Habitat and Ecology:	It once inhabited dry to moist `ohi`a-koa forest and woodlands, but it later became confined to high mountain forest. It is omnivorous, but primarily feeds on the fruit of native understory plants^5,6. As well as fruits and berries, the species feeds on eggs, young birds, insects and carrion⁸. Captive-reared birds have been observed using twigs as tools to access food⁸. Nest construction usually begins in March and the first clutches are laid in April¹².
Systems:	Terrestrial

Habitat and Ecology:

It once inhabited dry to moist `ohi`a-koa forest and woodlands, but it later became confined to high mountain forest. It is omnivorous, but primarily feeds on the fruit of native understory plants^5,6. As well as fruits and berries, the species feeds on eggs, young birds, insects and carrion⁸. Captive-reared birds have been observed using twigs as tools to access food⁸. Nest construction usually begins in March and the first clutches are laid in April¹².

Systems:

Terrestrial

Threats [top]

Major Threat(s):	It has suffered from extensive habitat alteration, particularly reduction of understory food-plants as a result of the activities of feral ungulates, logging, agriculture and the loss of pollinators and dispersers⁶. Problematic ungulates include feral cattle, mouflon sheep, feral sheep and goats¹¹. The impact of shooting has probably been substantial, even in recent decades. In the late 19th Century, ranchers, cowboys and coffee farmers persecuted the species as a pest, and it became unpopular with pig hunters for alerting animals to their presence⁸. The species was confiding and easily attracted by imitated calls, making it an easy target⁸. During breeding the species is sensitive to human disturbance⁸, including nest-monitoring operations⁹. Other documented threats include predation by introduced rats, the small Asian mongoose Herpestes javanicus and the native Hawaiian Hawk Buteo solitarius (classified as Near Threatened), as well as avian malaria and pox carried by introduced mosquitoes⁵and Toxoplasma gondii carried by feral cats^11,12. Feral cats are ubiquitous in the species's habitat and are also potential predators¹¹. Fledged chicks remain near the ground for several days before they can fly properly and are at particular risk from predation⁸. Captive-reared birds have suffered from disease, with at least one dying from a bacterial infection, and diseases may have made others more vulnerable to predation^1,5. The captive population is inbred⁸, and this may be reducing reproductive success. West Nile Virus, which could potentially be introduced by migrating shorebirds and waterfowl or commercial transport, and is spread by mosquitoes⁸, could threaten reintroduction efforts in the future. West Nile Virus is presumed to be highly lethal in C. hawaiiensis, owing to a reduction in the population of the American Crow C. brachyrhynchos in mainland North America by 45% over eight years due to the virus¹¹.

Major Threat(s):

It has suffered from extensive habitat alteration, particularly reduction of understory food-plants as a result of the activities of feral ungulates, logging, agriculture and the loss of pollinators and dispersers⁶. Problematic ungulates include feral cattle, mouflon sheep, feral sheep and goats¹¹. The impact of shooting has probably been substantial, even in recent decades. In the late 19th Century, ranchers, cowboys and coffee farmers persecuted the species as a pest, and it became unpopular with pig hunters for alerting animals to their presence⁸. The species was confiding and easily attracted by imitated calls, making it an easy target⁸. During breeding the species is sensitive to human disturbance⁸, including nest-monitoring operations⁹. Other documented threats include predation by introduced rats, the small Asian mongoose Herpestes javanicus and the native Hawaiian Hawk Buteo solitarius (classified as Near Threatened), as well as avian malaria and pox carried by introduced mosquitoes⁵and Toxoplasma gondii carried by feral cats^11,12. Feral cats are ubiquitous in the species's habitat and are also potential predators¹¹. Fledged chicks remain near the ground for several days before they can fly properly and are at particular risk from predation⁸. Captive-reared birds have suffered from disease, with at least one dying from a bacterial infection, and diseases may have made others more vulnerable to predation^1,5. The captive population is inbred⁸, and this may be reducing reproductive success. West Nile Virus, which could potentially be introduced by migrating shorebirds and waterfowl or commercial transport, and is spread by mosquitoes⁸, could threaten reintroduction efforts in the future. West Nile Virus is presumed to be highly lethal in C. hawaiiensis, owing to a reduction in the population of the American Crow C. brachyrhynchos in mainland North America by 45% over eight years due to the virus¹¹.

Conservation Actions [top]

Conservation Actions:	Conservation actions underway: Between 1993 and 1999, over 40 birds were hatched in the captive breeding programme⁹. Captive-raised individuals were released into lightly-managed habitat and monitored^3,4, but releases were stopped after January 1999 due to increasing mortality¹¹. About 75 birds need to be maintained in the captive flock for future reintroduction attempts to take place¹¹. Introduced mammalian predators were trapped in the Kona Forest Unit and, although this no longer takes place, predators would be managed at any future reintroduction site¹¹. Some areas of its former range are now fenced and free of feral ungulates, and the exclusion of ungulates will be extended into other areas¹¹. Relocation of problematic B. solitarius failed because the birds homed back from over 32 km¹. A recovery plan has been prepared, other potential release-sites have been investigated, and site preparations are being planned¹¹. Each year, around 2,000 school children and students attend the environmental education programme and see C. hawaiiensis in captivity at the Keauhou Bird Conservation Centre⁸. Conservation actions proposed: Restore and manage a significant proportion of remaining habitat within the species's historical range. Deal creatively with the problem posed by B. solitarius^1,5,6. Reintroduce birds to habitat managed to reduce major threats. Exclude ungulates from more areas of habitat. Control potential predators and vectors of disease in the species's former range.

Conservation Actions:

Conservation actions underway:

Between 1993 and 1999, over 40 birds were hatched in the captive breeding programme⁹. Captive-raised individuals were released into lightly-managed habitat and monitored^3,4, but releases were stopped after January 1999 due to increasing mortality¹¹. About 75 birds need to be maintained in the captive flock for future reintroduction attempts to take place¹¹. Introduced mammalian predators were trapped in the Kona Forest Unit and, although this no longer takes place, predators would be managed at any future reintroduction site¹¹. Some areas of its former range are now fenced and free of feral ungulates, and the exclusion of ungulates will be extended into other areas¹¹. Relocation of problematic B. solitarius failed because the birds homed back from over 32 km¹. A recovery plan has been prepared, other potential release-sites have been investigated, and site preparations are being planned¹¹. Each year, around 2,000 school children and students attend the environmental education programme and see C. hawaiiensis in captivity at the Keauhou Bird Conservation Centre⁸.

Conservation actions proposed:

Restore and manage a significant proportion of remaining habitat within the species's historical range. Deal creatively with the problem posed by B. solitarius^1,5,6. Reintroduce birds to habitat managed to reduce major threats. Exclude ungulates from more areas of habitat. Control potential predators and vectors of disease in the species's former range.

Citation:	BirdLife International 2008. Corvus hawaiiensis. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.2. <www.iucnredlist.org>. Downloaded on 21 November 2009.
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