Hawaiian crow

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, ‘elepaio, and ʻapapane. The ʻalalā also commonly forages on flowers, especially from February through May. Nectar to feed the young are 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 ʻalalā only occasionally forages on the ground, but only for a limited amount of time for risk of predators.[2]

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.[10][11][12]

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.[8]

This is a medley of the different calls the Hawaiian Crow makes.[13]

Female crows are considered sexually mature at about 2 or 3 years of age and males at 4 years.[14] 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.[15] 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.[8]

Avian malaria is a parasitic disease of birds, caused by Plasmodium relictum, a protist affecting birds in all parts of the world. Usually this disease does not kill birds, however in an isolated habitat such as Hawaii, birds have lost evolutionary resistance and are unable to defend against the novel protist. Its main vector is the mosquito Culex quinquefasciatus, introduced to the Hawaiian islands in 1826. This introduction can be attributed to birds club that brought nonnative species to replace birds that fell victim to the Avipoxvirus. At least 100 introductions have been documented in this manner.

The ʻalalā has been legally protected by the state of Hawaii since 1931 and was recognized as federally endangered in 1967. Sites on the slopes of Mauna Loa and other natural ranges have been set aside for habitat reconstruction and native bird recovery since the 1990s. The Kūlani Keauhou area has been ranked the best spot for the crows, parts of which have been fenced and ungulate-free for 20 years, helping tremendously for habitat recovery.[8]

Restoration programs for the Hawaiian crow require the collaboration from private land-owners, National Biological Service (NBS) biologists, US Fish and Wildlife Service (Service) biologists, and the State of Hawaii. In 1993 and 1994, 17 eggs were removed from wild nests and transported to a temporary hatcher in Kona District, Hawaii. Puppets mimicking adult crows were used to feed chicks to minimize the possibility of abnormal imprinting or human socialization. Three of the removed eggs were infertile, 13 chicks hatched, and 12 ʻalalā were successfully reared. One egg failed to hatch because of embryonic malpositioning, and another chick died from yolk-sac infection.[22]

In December 2016, five juvenile male Hawaiian crows were released into the Pu'u Maka'ala Natural Area Reserve on the Big Island, marking the first time the birds had been present in the wild since 2002.[23] However, within a week of reintroduction, three of the five birds were found dead.[24] Two of the deaths were caused by the Hawaiian hawk, and the other death was due to starvation.[24] The remaining two crows were taken out of the wild.

On September 26, 2017, 6 crows were released into the Pu'u Maka'ala Reserve. In contrast to the previous release, the group released was made of 4 males and 2 females rather than just males.[25] On October 11, 2017, another group of 5 crows, 3 males and 2 females, was also released into the area. The first group introduced also formed social groups similar to those expected of the species, and also responded to stressors in the environment, showing awareness of surroundings.[26] As of 2018, they have been described as "thriving", though they may have been negatively affected by the 2018 lower Puna eruption, which impacted at least a third of the Malama Kī Forest Reserve, an important habitat for the Hawaiian crow and other endangered Hawaiian wildlife.[27][28] Following the success of the previous year's introduction, another 5 were reintroduced to the Pu'u Maka'ala Reserve on September 25, 2018.[29] In late 2018, one of the crows released in 2017, a male named Maka'ala, was found dead due to wounds likely from a predatory attack followed by scavenging.[30]

In May 2019, two of the released crows, Mana’olana and Manaiakalani, were spotted building a nest with the female incubating eggs, marking the first wild breeding attempt made by Hawaiian crows since the extinction of the species in the wild. However, the eggs never hatched and were later presumed to be infertile, although occasionally laying infertile eggs is not uncommon for the species.[31]

In attempt to save the ʻalalā, efforts have been made to breed the species in captivity. A majority of these efforts have proved to be highly unsuccessful. Studies have shown that females are the primary nest builders, and if the male hangs around the nest for too long and attempts to sit in it, the female either ceases her efforts to complete the nest or in other cases, builds up aggression between the breeding pair. This disruptive behavior can inhibit the production of eggs. On average, clutch size bred in captivity is much lower than it has been observed in the wild. This can be attributed to thin eggshells as a result from inbreeding, and behavioral complications from males. Bred in isolation, some males exhibit aggressive behavior towards their mates and an inability to understand friendly gestures. For the best breeding success, it is important for cages to mimic real environmental behavior, and socially-reared males are put together with the females.[32]

On April 16, 2009, The U.S. Fish and Wildlife Service announced a five-year plan to spend more than $14 million to prevent the extinction of the Hawaiian crow through protection of habitats and management of threats to the species.[33]