The palila (Loxioides bailleui) is a critically endangered finch-billed species of Hawaiian honeycreeper. It has a golden-yellow head and breast, with a light belly, gray back, and greenish wings and tail. The bird has a close ecological relationship with the māmane tree (Sophora chrysophylla), and became endangered due to destruction of the trees and accompanying dry forests. The first specimen of the palila was collected in 1876 at the Greenwell Ranch on the Big Island by Pierre Étienne Théodore Ballieu (1828–1885), who was French consul in Hawai‘i from 1869 to 1878. The type specimen (No. 1876-645) is housed at the Muséum national d'histoire naturelle in Paris.
Taxonomy
The Hawaiian honeycreepers (Drepanididae) are sometimes included in the true finch family (Fringillidae). Oustalet scientifically described the palila in 1877. Named Loxioides bailleui by him, it was for some time united with several other "parrot-billed" Hawaiian honeycreeper species in Psittirostra. Currently, the palila has again been moved to genus Loxioides, which was long considered monotypic. The native name ōū poopapale ("capped ōū") probably refers to this species too. Despite its bill and habits being somewhat similar to the ōū, its color pattern betrays a very close relationship with the genus Telespiza.
Description
The palila has a yellow head and breast, with white to light gray plumage ventrally, medium gray plumage dorsally, and olive-green wings and tail. The bird also has a heavy dark bill with swollen sides, a brown iris, and dark feet with yellowish soles. The palila is one of the largest living Hawaiian honeycreepers, measuring around . With a body mass of on average in males and , it appears to be the heaviest Hawaiian honeycreeper.
There is some sexual dimorphism. Males tend to have brighter colors overall, as well as clear-cut black lores. The corresponding area contrasts less with the dirty-yellow heads in the marginally smaller females.
The bird's song is inconspicuous, containing whistling, warbling and trilling notes. The call is characteristic, however, being a clear, bell-like whistle, chee-clee-o or te-cleet. This is loudly communicated between birds advertising food during the morning and evening, and according to native informants, it is given most frequently during the day as rain approaches.
Distribution and status
Currently, the palila can be found only on the upper slopes of Mauna Kea on the island of Hawaii. Palila live from about MASL. The population density of the bird increases in areas where māmane (Sophora chrysophylla) grows more plentifully, and the birds do not appear to venture far from māmane stands. Essentially, this means that the species is confined – and may always have been so – to the area above the moist forest belt at around .
The fossil record shows that prior to human arrival the Palila also occurred in Kauai and Oahu, and thus could likely have occurred on Maui and neighboring islands as well, but it has not been recorded out of the island of Hawaii since European arrival. Palila are found in less than 10 percent of their historical range; they were found at elevations down to as late as the 19th century. Loxioides bailleui was abundant throughout Hawaii until the beginning of the 20th century. It lived on the upper slopes of Mauna Kea, the northwest slopes of Mauna Loa, and the eastern slopes of Hualālai. Then, as early as 1944, scientists believed the bird almost extinct.
On March 11, 1967, the palila was listed as an endangered species under the Endangered Species Act. In 1975, it was estimated that only 1,614 palila existed. In 1978, the 9th Circuit Court of Appeals ruled that feral sheep and goats had to be removed from critical habitat of the bird. From annual counts between 1980 and 1996, variable estimates of population ranged from 1,584 to 5,685 mature birds, though there are no consistent trends. In 1997, the west slope of Mauna Kea contained 72% of the population. The entire population, an estimated 4,396 birds, occupied an estimated .
Conservation
The remaining habitat of the palila is actively being preserved, with public access being limited to nature trails such as the Palila Forest Discovery Trail on Mauna Kea. The San Diego Zoo has a captive breeding program for the palila based in the Keauhou Bird Conservation Center on Hawaii Island. In May 2019, 6 palila were reintroduced to a patch of restored forest on the island in order to establish a second population, marking the first reintroduction attempt for the species.