Haleakala means "house of the sun" and is also the name of the active shield volcano that forms the eastern part of the Hawaiian Island of Maui. The Haleakala Important Bird Area encompasses most of the higher elevations of the volcano, from near sea level on the northern coast to the summit at 3,055 meters (10,023 feet). Prevailing northeasterly trade winds cause high rainfall on the northern and eastern slopes, while the southern and western sides of the mountain are drier. Annual rainfall ranges from about one meter (39.3 inches) in the southwest to over seven meters (275 inches) at around 1,000 meters elevation on the northeastern face. The northern and eastern slopes are covered in dense rainforest, the southern and western slopes support dry shrubland and mesic forest. Vegetation becomes shorter at higher elevations, giving way to subalpine shrubland and grassland above about 2,000 meters (6,600 feet). The crater and summit of Haleakala consist of bare lava and ash punctuated by many cinder cones, with only sparse vegetation. Three large canyons cut the flanks of Haleakala, Ko`olau Gap on the north and Kaupo Gap and Kipahulu Valley on the south. The windward slopes in particular have been eroded by numerous streams. Dense rainforests on the northern and eastern slopes have hindered human development, and these areas contain some of the most intact native ecosystems in Hawai`i. The drier southern and western slopes have been extensively altered by human development, timber harvesting, grazing, and agriculture. Invasive alien plants dominate much of the lowlands on all sides. The area is 46,602 hectares (115,106 acres) in size and includes Haleakala National Park, Hanawi State Natural Area Reserve, Ko`olau, Hana, Kipahulu, Kahikinui, Kula, and Makawao State Forest Reserves, Polipoli Spring State Recreation Area, State Department of Hawaiian Home Lands, The Nature Conservancy's Waikamoi Preserve, and some private lands.
The Halekala IBA supports one of the greatest concentrations of endemic Hawaiian forest birds, including the entire population of several species that are endangered or of global conservation concern. The endangered Maui Parrotbill and Akohekohe or Crested Honeycreeper number about 500 and 3,700 individuals, respectively, and occur only in high elevation forests on northern and eastern Haleakala. The entire population of about 34,000 Maui Alauahio is also restricted to east Maui. Haleakala supports about 18,000 `I`iwi, another species of global conservation concern. `Apapane and Hawai`i `Amakihi occur on other islands and are somewhat more numerous at about 93,000 and 44,000 individuals, respectively, but these represent a large proportion of each species' total population. The remote forests of east Maui are the last possible refuge for two extremely rare endemic birds, the Po`ouli and Nukupu`u. The last known Po`ouli died in captivity in 2005, before a mate could be located, and no wild birds have been observed since. The Nukupu`u has not been observed on Maui since 1996, when a single bird was seen, and may be extinct. If either of these species still survive it is somewhere within the Haleakala IBA. Their status cannot be known with certainty until the most remote areas of Maui have been adequately searched.
The endangered Nene or Hawaiian Goose was reintroduced to Maui starting in 1985, and the crater area of Haleakala now supports an important population of about 250 birds. Haleakala also supports one of the largest breeding populations of the endangered Hawaiian Petrel. Several hundred pairs nest in burrows among lava rocks near the summit and around the crater rim, where they are protected and find some safety from introduced predators.
Habitat and land use
The Haleakala IBA contains a wide range of habitats, from dense rainforest to subalpine shrubland and bare lava and cinder. The northern and eastern slopes of the mountain are wetter than the southern and western slopes due to prevailing northeasterly tradewinds that carry moist air across the Pacific. Rainfall increases with elevation due to adiabatic cooling and condensation that occurs as air is forced upward over the mountain slopes. Annual rainfall ranges from about one meter (39 inches) in the southwest to over seven meters (275 inches) between 1,000 and 1,200 meters elevation in the northeast. Dense rainforest covers most of the northern and eastern slopes. The middle elevations are often cloaked in clouds and mist for days at a time and are covered with dripping, moss-shrouded cloud forest. The rainforests and cloud forests of east Maui have been protected from disturbance by their remoteness, rugged terrain, and high rainfall and are some of the least disturbed native habitats in Hawai`i. `Ohi`a is the dominant canopy tree in most areas, but the forest is diverse and contains many endemic and endangered plant species. The dry shrubland and mesic forest habitats on the leeward side are more disturbed and much of the forest has been removed for timber and grazing, but remnant groves of koa trees occur in some areas. Haleakala is an active volcano, and the lunar-like summit area and 12 km-wide crater consist of bare lava, ash, and cinder. Vegetation is sparse in this area, but the spectacular Haleakala silversword is found only here.
Almost all of the land comprising the Haleakala IBA is zoned for conservation and used for some sort of conservation purpose. Haleakala National Park is managed for the protection of natural and cultural resources and for public use. The park contains a campground, numerous hiking trails, and several cabins available for overnight use. The Kipahulu section of Haleakala National Park and Hanawi State Natural Area Reserve are used strictly for conservation and research purposes and access is controlled. Waikamoi Preserve is also used for conservation purposes, and guided nature walks are available in one area of the preserve. Public hunting of non-native ungulates, primarily feral pigs, is permitted in all state forest reserves, but most hunting occurs in the more accessible sections. Birdwatching, hiking, sightseeing, and photography are also popular activities.
Pressure/threats to key biodiversity
The greatest threats to forest birds at Haleakala are diseases carried by alien mosquitoes, invasive alien plants, alien ungulates, and predation by alien mammals. The parasite that causes avian malaria and the alien mosquito that carries malaria and avian pox virus cannot tolerate cold temperatures, so most forest birds are found primarily in the highest, coldest parts of the island above about 1,500 meters (5,000 feet) elevation. Some species with greater immunity, such as `Amakahi and `Apapane, can be found at lower elevations. Global warming may allow mosquitoes to increase in range, reducing the amount of disease-free habitat. Invasive alien plants displace native plants needed by forest birds for nesting and foraging and often grow in monocultures that reduce floristic diversity. Some of the worst invasive plants are Miconia calvescens, strawberry guava, christmasberry, and black wattle. Feral pigs degrade native forest habitat by uprooting understory plants, preventing regeneration of native trees, spreading the seeds of invasive alien plants, and creating wallows where mosquitoes breed. Browsing by feral sheep has caused extensive damage to forests on leeward slopes, though efforts are underway to fence remnant koa forests in the Kahikinui area. Feral axis deer are increasing in number in some areas and their browsing is also damaging forest habitat. Black rats are the most serious predator on nests of many forest birds. Mongoose and feral cats are the most serious predators on ground-nesting birds like Nene and Hawaiian Petrels. Predators are controlled in parts of Haleakala National Park and Hanawi State Natural Area Reserve. Collisions with vehicles are a cause of mortality for Nene, and this problem is exacerbated by public feeding even though this practice is prohibited. In 2007 a fire in the Kula and Polipoli area on the southwestern slope damaged forest habitat used by an isolated population of the Maui `Alauahio.
Most of the lands comprising the Haleakala IBA are owned by the State of Hawai`i (63%) and the National Park Service (25%). Haleakala IBA also includes Waikamoi Preserve (5%), which is managed by The Nature Conservancy and owned by Alexander & Baldwin, and some additional land owned by Alexander & Baldwin (7%). State lands include Hanawi Natural Area Reserve (7%), Department of Hawaiian Home Lands (6%), Ko`olau, Hana, Kipahulu, Kahikinui, Kula, and Makawao State Forest Reserves (50%), and Polipoli Spring State Recreation Area (<1%).