Abstract
The Hawaiian Islands arose from the sea through volcanic action and were subsequently inhabited by unique flora and fauna over a period of 10 million years. The delicate balance of the islands' small ecosystems was disrupted, however, when the first humans arrived, about 1,000 A.D. These Polynesian settlers began the decline of many Hawaiian birds by altering the environment through farming and the introduction of exotic plants, animals and insects.
As small numbers of settlers arrived sporadically their distrubance to the insular ecology was relatively minimal. As the population grew, however, human activities and impact increased, causing drastic and irreversible alterations. Edible plants naturally occuring on the islands were few, so tracts in the lowlands were cleared by fire for agriculture and habitation. Streams were diverted for irrigation. Domestic animals (dogs, pigs, and junglefowl) and plants such as yams, bananas, breadfruit, and taro were brought with the settlers. Others were also established inadvertently, such as weed seeds, lizards, and insects. Many of the colorful species of forest birds were hunted for their feathers to adorn capes and helmets for Polynesian cultural traditions.
In the world today species are threatened most commonly by habitat destruction, such as forest clearing, wetland drainage, livestock grazing, etc. Hawaii's birds face not only these problems but a myriad of others as well. Hundreds of introduced plant species have become widespread pests competing with native plants; some, such as Fountain grass, create fire hazards to forests as well. Man introduced exotic birds that became established and now compete with the indigenous populations for territory, food and nest sites. More incidiously, they are carriers of disease. Mammals and mosquitoes, however, have caused the most devastating effects by far.
Only two mammalian species are endemic to Hawaii-the Monk seal and a
species of hoary bat. All mammals currently inhabiting the islands were introduced deliberately or accidentally, and thus have no natural predators. The list is long: rats, pigs, goats, cats, mongooses, dogs, deer, sheep, wallabies, horses, and cattle. European sailors on early visits to the islands released sheep, goats, rabbits, and pigs so that on return visits they would be able to hunt and have fresh meat. Rats were unintentionally introduced; they vacated sailing vessels when in port. Rats quickly became serious agricultural pests, particularly in sugar cane fields. To save his crops, man intervenes with a scheme to introduce another mammal-one that would prey on the rats. The Indian mongoose was thus introduced from Jamaica. There was, however, a serious flaw in the plan: the mongoose is diurnal; the rats basically nocturnal. The mongoose does particularly relish birds and their eggs in its diet.
Introduced birds carrying avian pox and malaria were not a direct threat to native species until mosquitoes, vectors of those diseases, were introduced from ships' water barrels.
Evolving over millions of years without mammalian predators, native populations of many species of birds continue to be devastated by the introduced predators: mongooses, rats, pigs, dogs, cats and man. Grazing mammals destroy the native flora, often devouring seedlings of established plants, interfering with the natural cycle of reproduction; the mature plants are not being replaced by new generations. Pigs living in the forests disturb the vegetation when rooting about for edibles. In their foraging they leave tree fem stumps, which collect water and serve as ideal mosquito egg sites. Unfortunately ground-nesting birds and their eggs are also items in the pigs' diet.
Birds inhabiting islands generally have small populations and restricted ranges, and so are particularly vulnerable to outside disturbances and introductions of alien animals and plants. This is a com-
mon situation for insular environments universally. By the time the first European arrived in the Hawaiian Islands (Captain Cook in 1778) 2 5 species of birds had already become extinct; 29 species or sub-species are currently endangered.
Realizing the precarious situation of many Hawaiian birds, the Territorial Government of Hawaii set up a captive breeding facility in 1949 at Pohakuloa on the ''Big Island'' (Hawaii), which has since become a large complex of pens on 5 acres of land. The Endangered Species Project is located half-way up Mauna Kea, a 13,784' snow-capped mountain opposite Mauna Loa a 13,680' mountain and active volcano. The Project is manned by a staff of two full-time State employees, Ah Fat Lee and Clyde Saragosa. Three species of endangered native waterfowl are being propagated there: the Koloa duck, Nene goose, and Laysan teal, as well as a severely endangered passerine known as the 'Alala (Hawaiian crow). Prior to their establishment at Pohakuloa, captive 'Alala, were maintained at Volcanoes National Park under the auspices of the United States Fish and Wildlife Service.
A little smaller in size and browner in color (as opposed to purplish feather gloss) than the common North American crow, the' Alala (Corvus tropicus) is now found only in limited segments of its original ranges of rnontane rain forest on the Big Island. The estimate for the wild population of crows is 30 to 40 individuals. Unfortunately, the factors causing their decline are still actively affecting them or even accelerating.