|Most recent IBA monitoring assessment|
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Lehua Islet is a small, rocky, volcanic island 1.2 kilometers north of Niihau and 31 kilometers west of Kauai. The volcanic tuff crater that formed Lehua 4.9 million years ago is now highly eroded and nearly half submerged, forming a steep, crescent-shaped island with an area of 117 hectares, a length of 2 kilometers, and a maximum elevation of 213 meters. The upper slopes of the inner crescent are composed of parallel strata that have eroded at different rates, producing a series of weathered ledges 1-2 meters wide and 1-2 meters high. The lower slopes of the inner crescent are eroded into chasms and fissures. The outer slopes are smoother, but have several eroded gullies that widen near the shore. Cliffs up to 55 meters high occur on the eastern and western points. The shoreline is rocky and often washed by large waves, especially in the winter. Lehua is in the rain shadow of Kauai and is very dry, especially during the heat of summer. Much of the island is bare rock, eroded sediment has collected only in gully bottoms, ledges, and small caves. Vegetation is sparse but many plants have a growth spurt after winter rains. Rabbits and rats introduced over 70 years ago severely altered the islet's ecosystem by decimating native plants, allowing alien plants to dominate, and impacting smaller seabird species. The eradication of feral rabbits in 2005 has allowed recovery of some native plants but also the proliferation of several invasive weeds. An attempt to eradicate Pacific rats (Rattus exulans) in 2009 failed and rats are still present on the island. Lehua is owned by the U.S. Coast Guard and managed by the State of Hawaii as a seabird sanctuary. There is no evidence of permanent human habitation, but several stone structures built by ancient Hawaiians are present, and Hawaiians probably visited Lehua to fish and to harvest seabirds, feathers, and eggs. The federal government built a lighthouse on Lehua in 1932 that was replaced by a solar powered light in 1989, which is maintained by the Coast Guard.
Lehua Islet is important for the number and diversity of breeding seabirds it supports and for the presence of several seabird species that are rare or have restricted breeding ranges. Recent surveys documented over 25,000 pairs of 11 seabird species nesting or attempting to nest on Lehua. Wedge-tailed shearwaters are the most numerous species on the island, with an estimated 23,000 pairs. The Brown Booby colony on Lehua is the largest in the Hawaiian Islands with 521 breeding pairs, and the Red-footed Booby colony is one of the two largest in the Hawaiian Islands, with 1294 pairs and approximately 4288 total individuals. The colonies of Laysan Albatross (28 pairs, 93 total individuals) and Black-footed Albatross (16 pairs, 53 total individuals) are small but appear to be growing and are important because these species have restricted breeding distributions and Lehua is one of the few high islands where they nest. Other species nesting on the islet include Christmas Shearwater, Bulwer's Petrel, Red-tailed Tropicbird, and Black Noddy. Newell's Shearwater, which is listed as threatened under the U.S. Endangered Species Act, and Band-rumped Storm-Petrel, a candidate for listing, attempt to nest on Lehua in small numbers, but predation by alien rats makes it difficult for these small seabirds to nest successfully. These species appear to be declining in Hawaii and may be difficult to manage on the larger Hawaiian Islands. Offshore islets such as Lehua may become increasingly important in the conservation of these species because their small size makes it more feasible to eradicate predators and manage other threats.
BirdLife International (2020) Important Bird Areas factsheet: Lehua Islet. Downloaded from http://www.birdlife.org on 19/02/2020.