Hawaiian crow
The Hawaiian crow or alalā 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, but with more rounded wings and a much thicker bill. It has soft, brownish-black plumage and long, bristly throat feathers; the feet, legs, and bill are black. Today, the Hawaiian crow is considered the most endangered of the family Corvidae. 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.
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 and 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.'' 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.The Hawaiian crow was also preyed on by rats and the small Asian mongooses. Feral cats that introduced Toxoplasma gondii to the birds can also prey on chicks that are unable to fly. As of 2012, the Hawaiian crow's current population is 114 birds, the vast majority of which are in Hawaiian reserves.
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.This 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 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.Environmental role
The alalā was one of the largest native bird populations in Hawaii. Its disappearance in the wild has had cascading effects on the environment, especially with the seed dispersal of the native plants. Many of these plants rely on the alalā not only for seed dispersal but also for seed germination as seeds are passed through the crow's digestive system. Without seed dispersal, the plants have no means of growing another generation. The alalā plays a key role in the maintenance of many indigenous plant species, which now could become a rarity in Hawaii's ecosystems, specifically the dry forests, without their main seed disperser. The Hawaiian crow has become known as an indicator species; the disappearance of the alalā indicates serious environmental problems.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.Polynesian cultures valued alalā feathers for use in kāhili and for decorating idols used during the Makahiki season. For this purpose, professional birdcatchers working for King Kamehameha or local priests were known to snare and hunt alalā with poles.
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, a hawk species endemic to Hawaii.Several mammal species introduced to Hawaii by humans are known to prey on alalā eggs, nestlings, and fledglings. These include the roof rat, the small Indian mongoose, and feral cats, which have been known to attack nests, eat eggs, and kill young fledglings.