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Site description (2011 baseline):
Site location and context
The Hamakua Forest Important Bird Area is located on the eastern flank of Mauna Kea volcano on the island of Hawaii. It encompasses about 51,168 hectares (126,436 acres) of predominantly native forest extending from about 450 to 2,130 meters (1,500 to 7,000 feet) elevation. The 13,252-hectare Hakalau Forest National Wildlife Refuge is the centerpiece of the IBA and was established in 1985 specifically to protect populations of endangered forest birds and their habitat. The IBA also encompasses adjacent parcels that contain additional important habitat, including Laupahoehoe State Natural Area Reserve, Hamakua, Hilo, Hilo Watershed, and Manowaiale`e State Forest Reserves, and several privately-owned parcels. Together, these lands form the single largest area of intact native forest in the Hawaiian Islands. The terrain consists of gentle to moderate slopes with steep rocky gulches cut by numerous streams. Rainfall is high throughout the area, peaking at over 6 meters per year around 500 meters elevation and declining gradually upslope. The lower and middle elevations are covered in dense `ohi`a and `ohi`a-koa rainforest. The upper elevations support mesic koa-`ohi`a woodland. The upper forest boundary in many areas is an abrupt, unnatural edge created by koa timber harvesting and clearing of forest for cattle ranching. The lower forest boundary is also abrupt in some areas due to clearing of forest for sugar cane cultivation. Most of the area is dominated by native plant species, but alien plants are common along the edges and dominate some areas, particularly at lower elevations. The dense vegetation, high rainfall, and steep stream gullies of the Hamakua region have limited human use and helped to protect it from disturbance and development, and it remains one of the most remote and little-visited areas in Hawai`i.
The Hamakua Forests IBA supports one of the most important remaining concentrations of endemic Hawaiian forest birds, including the largest populations of three species that are endemic to the island of Hawaii and listed under the U.S. Endangered Species Act, the `Akiapola`au (Hemignathus munroi), Hawai`i Creeper (Oreomystis mana), and Hawai`i `Akepa (Loxops coccineus). Several species reach their highest density in Hakalau Forest National Wildlife Refuge, which forms the core of their distribution. Although Hakalau comprises only 20% of the land area in the IBA, it harbors 50% of `Akiapola`au (50%), 49% of Hawai`i Creeper, and 72% of Hawai`i `Akepa. The endangered `Io or Hawaiian Hawk is widespread and observed frequently over much of the area. The Hamakua area also supports important populations of three other endemic Hawaiian forest birds of global conservation concern, the `I`iwi (Vestiaria coccinea), Oma`o (Myadestes obscurus), and Hawaii `Elepaio (Chasiempis s. sandwichensis). The `Apapane (Himatione sanguinea) and Common (Hawai`i) `Amakihi (Hemignathus virens) are the most abundant native birds in the IBA and also occur on other islands, but still have globally restricted ranges. The endangered Nene or Hawaiian Goose (Branta sandvicensis) has been reintroduced at Hakalau Forest NWR, and about 200 birds now inhabit the area.
The Hamakua Forest IBA is located between 450 to 2,130 meters (1,500 to 7,000 feet) elevation on the eastern flank of Mauna Kea Volcano on island of Hawai`i. The terrain consists of gentle to moderate slopes with steep rocky gulches cut by numerous streams. Rainfall is high throughout the area, peaking at over 6 meters per year around 500 meters elevation, declining gradually upslope. The lower and middle elevations (600 ? 1,900 meters) are covered in dense native rainforest where `ohi`a (Metrosideros polymorpha) and koa (Acacia koa) are the dominant canopy trees and common understory trees and shrubs include `olapa (Cheirodendron trigynum), kolea (Myrsine lessertiana), pilo (Coprosma spp.), tree ferns (Cibotium spp.), pukiawe (Leptecophylla tameiameiae), ohelo (Vaccinium calycinum), and akala (Rubus hawaiiensis). Below 1,200 meters dense mats of `uluhe fern (Dicranopteris linearis) cover some areas. The upper elevations (>1,900 meters) support mesic woodland dominated by koa and `ohi`a, with mamane (Sophora chrysophylla) and naio (Myoporum sandwicense) in some areas. The upper forest boundary in many areas is an abrupt, unnatural edge created by koa timber harvesting and clearing of forest for cattle ranching. The lower forest boundary is also abrupt in some areas due to clearing of forest for sugar cane cultivation.
Most of the land comprising the Hamakua Forest Important Bird Area is used for conservation purposes. Dense vegetation, high rainfall, and numerous steep stream gullies have limited human use and helped to protect this area from disturbance and development, and it remains one of the most remote and little-visited areas of Hawai`i. Hakalau Forest National Wildlife Refuge contains several buildings used for management and research purposes, including a greenhouse and a biological field station. Sections of the refuge are open to limited public use, by permission, for wildlife viewing. An annual open house also provides wildlife viewing opportunities. The refuge also has an active volunteer service program for planting native tree seedlings and endangered plants, and alien plant control. Entry into Laupahoehoe Natural Area Reserve Natural Area Reserves is restricted by permit only to protect delicate natural ecosystems and prevent the spread of invasive species. The Hamakua, Hilo, Hilo Watershed, and Manowaiale`e Forest Reserves are used for conservation in addition to other purposes, primarily public hunting of feral pigs. Privately-owned lands are used for a variety of purposes, including conservation, forestry, and cattle ranching. Selective logging of koa trees by helicopter was proposed on two parcels owned by the misleadingly named private groups Hawaii Forest Preservation and Ohana Sanctuary, which in reality are associated with the logging company Koa Timber Inc., but permits to harvest koa were not approved by the State.
Pressure/threats to key biodiversity
The greatest threats to birds in the Hamakua Forest IBA are diseases carried by alien mosquitoes, invasive alien plants, alien ungulates, predation by alien mammals, and logging. Abundance of endemic forest birds is higher above 1,500 meters because the parasite that causes avian malaria and the alien mosquito that carries malaria and avian pox virus cannot tolerate cold temperatures. Nectarivorous `I`iwi and `Apapane move altitudinally in search of flowering trees and may be exposed to diseases when they descend. Global warming may allow mosquitoes to increase in range, reducing the amount of disease-free habitat. Feral pigs degrade native forest by uprooting understory plants, preventing regeneration of native trees, spreading seeds of invasive alien plants, and creating wallows and tree hollows where mosquitoes breed. Feral cattle destroy native forests and prevent regeneration by eating native understory plants and tree seedlings. 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 in the Hamakua area are strawberry guava (Psidium cattleianum), gorse (Ulex europaeus), blackberry (Rubus argutus), and banana poka (Passiflora mollissima). Miconia calvescens, an extremely invasive alien tree, occurs along the coast in Hamakua and is likely to spread. Black rats (Rattus rattus) are the most serious predator on nests of many forest birds. Mongoose (Herpestes auropunctatus) and feral cats prey on ground-nesting Nene. Non-native birds disperse the seeds of alien plants and may compete for food with native birds. Koa trees are harvested on some private lands and plans have been proposed for selective logging of koa on some state lands. Most of Hakalau Forest NWR is fenced against ungulates and feral pigs have been removed, and extensive reforestation efforts have resulted in planting of over 350,000 koa and other seedlings since 1989.
Lands comprising the Hamakua Forest Important Bird Area are owned by the Federal Government, the State of Hawai`i, and several different private landowners. Hakalau Forest National Wildlife Refuge is owned by the U.S. Fish and Wildlife Service. Laupahoehoe Natural Area Reserve and the Hamakua, Hilo, Hilo Watershed, and Manowaiale`e Forest Reserves are owned by the State of Hawai`i. Private landowners include Kamehameha Schools, Queen Liliuokalani Trust, and Parker Ranch. Despite their misleading names, two private parcels owned by Hawaii Forest Preservation and the Ohana Sanctuary are in reality associated with the logging company Koa Timber Inc.
Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Hamakua Forests (USA). Downloaded from
https://datazone.birdlife.org/site/factsheet/hamakua-forests-iba-usa on 23/11/2024.
