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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.
BirdLife International (2021) Important Bird Areas factsheet: Northwestern Hawaiian Islands. Downloaded from http://www.birdlife.org on 22/10/2021.