The Hawaiian crow or alalā (Corvus hawaiiensis) is a species of bird in the crow family, Corvidae, that is currently extinct in the wild, though reintroduction programs are underway. It is about the size of the carrion crow at in length, They are recorded to have lived up to 18 years in the wild, and 28 years in captivity. Some Native Hawaiians consider the Hawaiian crow an aumakua (family god).
The species is known for its strong flying ability and resourcefulness, and the reasons for its various extirpations are not fully understood. It is thought that introduced diseases, introduced predators, and habitat loss were probably significant factors in the species' decline.
Distribution and habitat
Before the Hawaiian crow became extinct in the wild, the species was found only in the western and southeastern parts of Hawaii. It inhabited dry and mesic forests on the slopes of Mauna Loa and Hualālai at elevations of 3,000 to 6,000 feet. Ōhia lehua (Metrosideros polymorpha) and koa (Acacia koa) were important tree species in its wild habitat. Extensive understory cover was necessary to protect the ʻalalā from predation by the Hawaiian hawk, or io (Buteo solitarius). Nesting sites of the ʻalalā received of annual rainfall. Fossil remains indicate that the Hawaiian crow used to be relatively abundant on all the main islands of Hawaii, along with four other now-extinct crow species.
Behavior
Diet
The omnivorous Hawaiian crow is a generalist species, eating various foods as they become available. The main portion of their diet and 50% of their feeding activity is spent foraging on trunks, branches, and foliage for invertebrates such as isopods, land snails, and arachnids. They feed in a woodpecker fashion, flaking bark and moss from trunks or branches to expose hidden insects, foraging mostly on ohia and koa, the tallest and most dominant trees in their habitats. Fruits are the second most dominant component in the Hawaiian crow's diet. The crows often collect kepau and olapa fruit clusters. Although hoawa and alani fruits have hard outer coverings, crows continue to exert energy prying them open. Passerine Nestlings and eggs are consumed most frequently in April and May, during their breeding season. Other prey include red-billed leiothrix, Japanese white-eye, Hawaiʻi ʻamakihi, ʻIʻiwi, ʻelepaio, and ʻapapane. The alalā also commonly forages on flowers, especially from February through May. Nectar to feed the young is obtained from the ohia flower, oha kepau, and purple poka during the nestling period. Crows also foraged various plant parts, including the flower petals of kolea, koa, and mamane. The palila is the only other Hawaiian bird known to eat flower petals. The alalā only occasionally forages on the ground, but only for a limited amount of time for risk of predators.
Tool use
Captive individuals can use sticks as tools to extract food from holes drilled in logs. The juveniles exhibit tool use without training or social learning from adults, and it is believed to be a species-wide ability.
Voice
The Hawaiian crow has a call described variously as a two-toned caw and as a screech with lower tones added, similar to a cat's meow. In flight, this species has been known to produce a wide variety of calls including a repeated kerruk, kerruk sound and a loud kraa-a-a-ik sound. It also makes a ca-wk sound, has a complex, burbling song, and makes a variety of other sounds as well. The alalā has at least 24 calls in its repertoire, including alarm calls, contact calls, and calls signifying submission or courtship.
link=|220x220pxThis is a medley of the different calls the Hawaiian Crow makes.
Breeding and reproduction
Female crows are considered sexually mature at about 2 or 3 years of age and males at 4 years. The Hawaiian crow's breeding season lasts from March to July; it builds a nest in March or April, lays eggs in mid-to-late April, and the eggs hatch in mid-May. Both sexes construct nests with branches from the native ohi'a tree strengthened with grasses. The crow typically lays one to five eggs (that are greenish-blue in color) per season, although at most only two will survive past the fledgling phase. Only the females incubate the 2–5 eggs for 19–22 days and brood the young, of which only 1–2 fledge about 40 days after hatching. If the first clutch is lost, the pair will re-lay, which serves to be helpful in captive breeding efforts. Juveniles rely on their parents for 8 months and will stay with the family group until the next breeding season. The Hawaiian crow has become known as an indicator species; the disappearance of the alalā indicates serious environmental problems.
thumb|The Hawaiian crow faces an ample number of threats in the wild.
Primary threats
The Hawaiian crow faces an ample number of threats in the wild, which are considered contributing factors to their extinction in the wild. Small population size makes the species more vulnerable to environmental fluctuations; this leads to a higher likelihood of inbreeding, which reduces the likelihood that offspring will survive to recruitment.
Habitat loss and hunting
Alalā select habitat with ample cover and prefer areas with a large proportion of native plants for food and shelter. Polynesian and European farmers removed dry, lowland forest, restricting the alalā to forest at higher elevation. After settlement by Europeans, the higher elevation forest was also compromised by extensive logging and ranching, and farm animals such as cattle, pigs, sheep, and goats being allowed to graze freely in these areas.
Alalā were also shot for sport by European colonizers. Though hunting native birds was illegal at the time, alalā continued to be shot throughout the 1980s, according to conservationists.
Introduced predators
The alalā's known extant natural predator is the 'io (Hawaiian hawk), a hawk species endemic to Hawaii. Though this disease appears in many passerine birds without much population impact, many isolated bird populations show significant mortality when introduced to this parasite, including native Hawaiian birds. Many Hawaiian bird species have shown precipitous population declines which are thought to be due to avian malaria.
Avian pox
Avian pox is an infection caused by viruses in the genus Avipoxvirus. Infection causes tumor-like lesions on the exposed skin of the legs and feet and in and around the beak, trachea, and esophagus. Avian pox is also spread by mosquitos, and through contact with infected birds or objects. In experimental studies on other native Hawaiian birds, avian pox has been shown to cause large lesions, which often become infected, leading to tissue necrosis. Infections can sometimes lead to death. Alalā have been known to become infected with avian pox, including during reintroduction efforts, but the role, if any, of the disease in their decline is unknown. Though toxoplasmosis rarely causes disease and death in infected animals, infection was diagnosed in five reintroduced alalā in 1998–1999. One presented with clinical signs and was successfully treated, three appeared to have died from the disease, and one was diagnosed but did not appear to show clinical signs of the disease. During reintroduction efforts between 2016–2020, several birds showed evidence in blood samples that they had had prior toxoplasmosis infections, though no birds tested positive for active infections. Whether or not toxoplasmosis has contributed to historic declines of alalā is unknown; however, it has been a consideration in conservation efforts for the species.
Status and conservation
left|200px|thumb|The Hawaiian crow has been extinct in the wild since 2002.
The Hawaiian crow is the most endangered corvid species in the world and the only corvid species left in Hawaii. Like other critically endangered species, harming the Hawaiian crow is illegal under U.S. federal law. By 1994, the overall population had dwindled to 31 individuals; 8 to 12 were wild and 19 held in captivity. and the species is now classified as Extinct in the Wild by the IUCN Red List. in two captive breeding facilities operated by the San Diego Zoo. Attempts to reintroduce captive-bred birds into the wild have been hampered by predation by the Hawaiian hawk (Buteo solitarius), which itself is listed as Near Threatened. Breeding efforts have also been complicated due to extensive inbreeding during the crow's population decline.
Protection
The alalā has been legally protected by the state of Hawaii since 1931 and was recognized as federally endangered in 1967. Because few chicks were produced each year and to prevent harm to the chicks from inept parents, birds were sometimes hand-reared without any siblings nearby. These individuals grew up to exhibit more stereotypies, a negative indicator for breeding success and fitness for release in the wild. Experimentation with allowing adults to incubate and rear their own chicks began in 2011, and by 2023, 17% of the living population was the product of full parent-rearing. Necropsies found that 2 of the deaths were likely due to predation by the Hawaiian hawk and 1 was due to natural circumstances stemming from poor body condition.
A program of improved predator training was implemented in response to the previous deaths, and between 2017–2019, 27 young alalā were released in the Pu'u Maka'ala Natural Area Reserve in 3 separate release cohorts. Though all birds released in 2017 and 2018 survived for over a year, birds released in 2019 survived for a shorter period- most died within 5 months of their release. Accelerating mortality into 2020 caused practitioners to recapture and return 5 surviving alalā to captivity. Another pair exhibited nest-building behavior, but did not succeed in building a full nest.
As of February 2024, plans are underway to release alalā on Maui, aiming for releases to begin in spring of 2024. Although alalā were known historically to exist only on the island of Hawaii, subfossil evidence has shown that alalā were found on Maui as recently as when humans began occupying the Hawaiian Islands. Because Maui has a similar landscape and plants to Hawaii but does not have any Hawaiian hawks, it is thought that alalā may be able to survive on Maui without a threat which caused the majority of deaths in prior reintroductions.
Cultural significance
The Hawaiian crow is a significant symbol in Hawaiian mythology. It is said to lead souls to their final resting place on the cliffs of Ka Lae, the southernmost tip on the Big Island of Hawaii. Native priests named the ʻalalā so during prayer and chants due to its distinctive call.
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