As part of the US state of Hawaii, this EBA comprises the islands of Kaua'i, O'ahu, Moloka'i, Lana'i and Maui, but not Hawai'i, which is considered an EBA in its own right (EBA 218; see also EBA 216), nor the two other (smaller) islands in the same group, Ni'ihau and Kaho'olawe, as nothing is known about their ornithological history and neither island is suitable now for native birds; goats were introduced to Ni'ihau in the late 1700s, and sheep and cattle had destroyed the original vegetation before the 1890s (Berger 1972).

Maui, at 1,861 km² the largest island in the EBA, reaches the highest altitude at Haleakala Volcano (3,055 m). The native vegetation is forest and woodland with two distinct types in the uplands, which are important for restricted-range birds: rain forest in the wetter areas (where the myrtaceous tree ohia Metrosideros polymorpha is dominant) and open, dry, woodland elsewhere (where koa Acacia koa is dominant).

The Hawaiian Islands are renowned for their unique wildlife, with 91% of flowering plants, 100% of land mammals and 81% of birds being endemic at least at subspecies level (Gagné 1988).

The majority of the restricted-range species of this EBA are taxonomically highly distinct, especially the Hawaiian honeycreepers. This endemic family is a particularly good avian example of adaptive radiation and speciation in an isolated island ecosystem for, from what is believed to have been a single successful colonization by an ancestral species from North America, its members have evolved into a diverse array of species and subspecies, e.g. Viridonia virens with a small insectivorous bill, Dysmorodrepanis munroi with a woodpecker-like bill and Vestiaria coccinea with a large decurved bill for nectar feeding. Five genera are endemic to the EBA-Dysmorodrepanis, Melamprosops, Palmeria, Paroreomyza and Pseudonestor.

The taxonomy of the species of these islands is still in a state of flux such that populations of Chasiempsis sandwichensis (which differ strikingly in plumage coloration among the three islands they inhabit) may prove to be separate species, and O'ahu Amakihi Viridonia virens chloris and Hawaiian Stilt Himantopus mexicanus knudseni are also treated as separate species by some experts (Pratt 1993, H. D. Pratt in litt. 1994).

Apart from two wetland species, all the restricted-range bird species are forest and/or woodland dwellers (mostly occurring in ohia rain forest), and many are restricted to higher altitudes (largely above 1,000 m), although historically they are likely to have occurred in lowlands too.

The distributional patterns of species vary considerably, with many island extirpations. Extant single-island endemics are found on Kaua'i (seven species), Maui (five), Moloka'i (one) and O'ahu (one), but all these islands are combined into one EBA with Lana'i because of the restricted-range species which are common to them (in various island combinations). Kaua'i and Maui are the most important islands both for their endemics and for the numbers of extant restricted-range species which they support in total (14 on Kaua'i and 11 on Maui).

Many species have tiny distributions within the islands on which they survive, with the Alaka'i Swamp on Kaua'i (a wet montane plateau mostly above 1,000 m) being a very important area, and the north-east slopes of Haleakala and upper Kipahulu valley on Maui being similarly important.

Two restricted-range species have been introduced: Nene Branta sandvicensis (from Hawai'i, EBA 218), introduced to Maui (184 birds present in 1989-1990) and Kaua'i (130 in 1995); and Micronesian Swiftlet Collocalia inquieta (from the Mariana and East Caroline Islands (EBAs 189, 192), established on O‘ahu from a flock introduced in 1962 (the race bartschi which is endemic to Guam).

Two seabirds, Hawaiian Petrel Pterodroma sandwichensis and Newell's Shearwater Puffinus newelli, are, as breeders, largely endemic to this EBA (otherwise likely to breed only, and in very small numbers, on Hawai'i, EBA 218).

Of all the Pacific EBAs, the Central Hawaiian Islands has the highest number of threatened restricted-range species (18), of threatened endemic restricted-range species (14), and of Critical endemic restricted-range species (eight). Several species with tiny populations have not been seen recently and are therefore likely to be close to extinction: Myadestes myadestinus (last seen on Kaua'i in 1989 with an unconfirmed sighting in 1993), M. lanaiensis (last seen on Moloka'i in 1988), Moho braccatus (last recorded on Kaua'i in 1987), M. bishopi (last seen on Maui in 1981 with subsequent reports from the 1980s unconfirmed), Psittirostra psittacea (last seen on Kaua'i in 1989) and Paroreomyza maculata (last confirmed sighting on O'ahu in 1985) (R. Pyle in litt. 1996).

The demise of the avifauna-documented by Pratt (1994) for the period 1893-1993 (see also Jacobi and Atkinson 1995)-has been due to a combination of factors: hunting by early settlers; forest clearance (most of the lowlands have been cleared for cultivation, grazing and settlement, and less than 40% of the land surface is covered with native-dominated vegetation); introduced predators (e.g. rats, cats, dogs and, except on Kaua'i, mongooses Herpestes auropunctatus); introduced browsers (e.g. pigs, deer, goats) and plants (such as the invasive neotropical tree Miconia calvescens) leading to habitat deterioration; introduced birds and arthropods (e.g. ants and wasps) resulting in increased competition for nesting and food resources; and diseases (especially viral pox and protozoan-caused avian malaria, carried by introduced Culex mosquitoes, which are common in wet mid-elevation forests where their populations overlap with highly susceptible native birds).

Since the late 1800s the human population in the Hawaiian Islands has grown exponentially, as has the tourist industry; the direct and indirect impacts of the resulting visitor load on the natural resources of the islands is an additional threat to wildlife (WWF/IUCN 1994-1995), although most native birds survive today in remote refuges where any disturbance is minimal (S. L. Pimm in litt. 1996).

These man-related threats can be exacerbated by cyclones, an irregular natural hazard. For example, Hurricane Iniki, which struck Kaua'i with devastating force in 1992, severely altered this legendary 'Garden Isle' by removing most of the forest canopy on exposed ridges. The island's extremely rare native birds, largely surviving in Alaka'i Swamp (and because of habitat alteration no longer able to ride out the storms in lowland valleys), may have been delivered the final death blow by this single event (Pratt 1993), there having been few or no records since.

In recent years the loss of species on Lana'i has accelerated as ecosystems have begun to suffer catastrophic collapse, and this serves as an example of what can happen to small-island systems when native flora and fauna are severely reduced (Hobdy 1993).

In addition to the 18 threatened restricted-range species in this EBA, three subspecies, which may be species-Chasiempsis sandwichensis ibidis, Viridonia virens chloris and Himantopus mexicanus knudseni-also qualify as threatened (H. D. Pratt in litt. 1994), and two endemic seabirds-Pterodroma sandwichensis and Puffinus newelli-(see 'Restricted-range species', above) are classified as threatened (both Vulnerable); P. sandwichensis has been reduced to c.900 pairs mainly on Haleakala on Maui, and P. newelli to c.8,000 breeding adults (perhaps more) on the mountains of Kaua'i.

There are many important parks and refuges in the Hawaiian Islands-for example, the Haleakala National Park (embracing the Kipahulu valley), which was established on Maui in 1916, and the more recently designated Alaka'i Wilderness Preserve, Koke'e and Waimea Canyon State Parks on Kaua'i-but much of the best remaining forest habitat remains unprotected and vulnerable (Pratt et al. 1987), and the long-term survival of native species within protected areas depends on the intensity of management, including programmes such as control of non-native species (IUCN 1992c).

One such programme has successfully controlled feral pigs in Kipahulu valley (Anderson and Stone 1993), an undertaking that has been described as the single most important management action for the protection of the biological diversity of east Maui's rain forests. Another programme is under way to remove Miconia calvescens from private and state land on Maui (Loope and Medeiros 1995), and further initiatives and recommendations are described in Stone and Loope (1987) and Medeiros et al. (1993). Major new efforts to develop strategies for monitoring transmission of diseases in remote forest habitats and for controlling vector populations are also in progress (Jacobi and Atkinson 1995). A detailed survey of Hawaiian forest birds (1976-1983) has resulted in a mass of distributional, population and habitat data, and in conservation recommendations for specific islands (Scott et al. 1986).

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Central Hawaiian Islands. Downloaded from https://datazone.birdlife.org/eba/factsheet/211 on 23/11/2024.