The Northwestern Hawaiian Islands (NWHI) Important Bird Area coincides with the Papahanaumokuakea Marine National Monument, which was established in 2006 and is the largest marine conservation area in the world. This vast, remote, and largely uninhabited area encompasses 362,061 square km of the central Pacific Ocean between 22? N and 30? N latitudes and 161? W and 180? W longitudes. The monument is 1,931 km long and 161 km wide and extends from subtropical latitudes to the northern limit of coral reef development. It includes 10 islands that were formed sequentially as the Pacific plate moved northwest over a hot spot, producing a series of shield volcanoes 7.3 million to 29.8 million years old. Erosion and subsidence has reduced these ancient volcanoes to small rocky islands or low atolls. Three of the easternmost islands (Nihoa, Necker, and Gardner Pinnacles) are steep and rocky. French Frigate Shoals is a near-atoll that contains two remnant volcanic pinnacles. Laysan and Lisianski are raised atolls. Maro, Pearl and Hermes, Midway, and Kure are true atolls with roughly circular rims and central lagoons. The islands have a total land area of 1350 hectares. All but four of them have an average height of less than 10 m, and the highest point is 274 m on Nihoa. The climate is mild year-round, with moderate humidity, persistent northeasterly trade winds, and infrequent storms. Annual rainfall averages 29 inches at French Frigate Shoals. Terrestrial habitats include sandy and rocky shores, coral rubble and reef flats, dunes, dry grassland and shrubland, rocky cliffs, a hypersaline lake on Laysan, and freshwater wetlands and water catchments on Midway and Kure. Marine habitats include abyssal basins over 4,500 m deep, submarine escarpments, banks at depths of 30-400 m, coral reefs, and shallow lagoons. These waters are critical foraging grounds for seabirds and provide a refuge from overfishing for pelagic fishes upon which many seabirds depend for efficient foraging.
Seabird colonies in the NWHI constitute one of the largest and most important assemblages of tropical seabirds in the world, with over 14 million birds of 21 species and 5.5 million birds breeding annually. They contain 99% of the worlds Laysan Albatrosses and 98% of the worlds Black-footed Albatrosses. The Laysan Albatross colony on Midway is the largest albatross colony in the world at over 617,000 pairs. Populations of several other seabirds are of global significance, including Bonin Petrel, Christmas Shearwater, Tristrams Storm-petrel, Gray-backed Tern, and Blue-gray Noddy. A few endangered Short-tailed Albatross have occasionally laid eggs on Midway, most of which have been infertile, but a single chick was fledged in 2011. Most seabirds breeding in the NWHI are pelagic feeders that obtain much of their food by associating with schools of large predatory fish, such as tuna and billfish. These seabirds are most successful at feeding their young when they can find schools of fish within commuting range of breeding colonies. The waters surrounding the islands are thus a crucial aspect of the ecosystem upon which these birds depend and an integral component of the IBA.
Four species of endangered birds are endemic to the NWHI, the Nihoa Finch, Nihoa Millerbird, Laysan Finch, and Laysan Duck. The Laysan Finch is relatively numerous, but populations of Nihoa Finch and Nihoa Millerbird are very small. In 2011, 24 Millerbirds were translocated from Nihoa to Laysan, where an endemic subspecies formerly occupied until 1923. Some birds are already nesting, but whether a breeding population becomes established remains to be seen. Laysan Ducks were once found throughout the Hawaiian Islands and were recently reintroduced to Midway, where a small population of about 50 birds is thriving.
Forty-seven species of shorebirds have been recorded in the NWHI. Most of these are infrequent visitors or vagrants, but the Monument supports significant populations of four migrants, Pacific Golden Plover, Bristle-thighed Curlew, Wandering Tattler, and Ruddy Turnstone. Most of these birds arrive in July and August and return to the arctic to breed in May, but some younger birds may skip breeding their first summer and remain in the Monument.
Habitat and land use
The NWHI support a diverse and unique array of marine and terrestrial habitats. The majority of the area consists of deep pelagic waters that surround the island platforms. Marine habitats include abyssal basins at depths of over 4,500 meters (15,000 feet), submarine escarpments, at least 15 banks at depths between 30 and 400 meters (100 and 1,300 feet), deep and shallow coral reefs, and shallow lagoons. These waters represent critical foraging grounds for seabirds and a refuge from overfishing for pelagic fishes upon which many seabirds depend for efficient foraging. Terrestrial habitats include sandy and rocky shores, coral rubble and reef flats, sandy dunes, dry coastal grasslands and shrublands, rocky cliffs, a hypersaline lake on Laysan, and freshwater wetlands and water catchments on Midway and Kure. Some of the most common plants include beach naupaka (Scaevola sericea), `ilima (Sida fallax), the native bunchgrass Eragrostis variabilis, and aweoweo (Chenopodium oahuense). Midway was extensively developed in the past for military and other uses, and contains paved runways and roadways, buildings, military fortifications, water catchments, and various other structures. Kure, Tern Island at French Frigate Shoals, and Laysan were developed to a lesser extent but still contain a few buildings and other man-made features.
The Northwestern Hawaiian Islands Important Bird Area coincides exactly with the Papahanaumokuakea Marine National Monument, which was established on June 15, 2006. Management of the Monument is the responsibility of three Co-Trustees, the State of Hawai?i, the U.S. Department of the Interior, Fish and Wildlife Service (FWS), and the U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA). The stated goals of the three trustees are to preserve the ecological integrity of the area and to perpetuate the native ecosystems of the NWHI, native Hawaiian culture, and other historic resources. The Secretary of Commerce, through NOAA, has primary responsibility regarding the management of the marine areas of the monument, in consultation with the Secretary of the Interior. The Secretary of the Interior, through FWS, has sole responsibility for the areas of the Monument that overlay the Midway Atoll National Wildlife Refuge, the Hawaiian Islands National Wildlife Refuge, and the Battle of Midway National Memorial, in consultation with the Secretary of Commerce. The Hawai?i State Department of Land and Natural Resources has primary responsibility for the Northwestern Hawaiian Islands State Marine Refuge and Hawai?i State Seabird Sanctuary at Kure Atoll.
Commerical fishing will be phased out within the monument, though a small amount of recreational fishing will be permitted on Midway as part of ecotourism. Midway is still used as an emergency landing site for commercial or military aircraft.
Pressure/threats to key biodiversity
Despite their remote location, the NWHI are threatened by a variety of factors, including marine pollution, contaminants, invasive plants, alien mammals, overfishing, vessel groundings, and climate change. Recent management actions have included eradication of black rats from Midway and Polynesian rats from Kure, eradication or control of invasive plants, cleanup of contaminants and other hazards at former military sites, and coordination with NOAA-Fisheries and Regional Fishery Management Councils to reduce fishing impacts.
Marine debris such as derelict fishing gear and nets poses an entanglement hazard for seabirds. Many young albatross die from accumulation of debris in their digestive system, such as disposable lighters and bottle caps, which are ingested by adults at sea and mistakenly fed to chicks. Albatross chicks on Midway also die by ingesting lead paint flakes from former military buildings, causing a fatal neural pathology known as ?droop-wing.? Low hatching success and impaired immune function in Black-footed Albatross have been linked to high levels of mercury and organochlorines. Ingestion of sand contaminated with carbofuran caused the deaths of Laysan Finches until the source was identified and removed by the FWS.
Climate change may be the most serious long-term threat to the NWHI. The higher temperatures, rise in sea level, changes in ocean chemistry, and more frequent and intense storms associated with global warming could inundate and hasten erosion of these low-lying islands, cause coral bleaching and inhibit coral growth, and destroy vital marine and terrestrial habitats.
Two of the worst invasive alien plants are golden crownbeard (Verbesina encelioides) and Sandbur (Cenchrus echinatus). Verbesina grows in dense stands that displace native plants and can kill albatross chicks by entanglement and heat exhaustion. Strict quarantine protocols are imposed to prevent further importation of invasive plants, animals, or insects.
Conservation responses/actions for key biodiversity
In 2011 24 Millerbirds were translocated from Nihoa to Laysan, where an endemic subspecies formerly occupied until 1923. Some birds are already nesting, but whether a breeding population becomes established remains to be seen.
A Small population of Laysan Duck have been reintroduced to Midway Island, where a population of about 50 birds is now thriving.
All of the Northwestern Hawaiian Islands are owned by the U.S. government except Kure, which is owned by the State of Hawaii.