Avifauna of Lehua Islet, Hawai‘i: Conservation Value and Management Needs.

Abstract

We conducted surveys from 2002 to 2005 and compiled historical information on the avifauna of Lehua Islet, Hawai‘i, to assess its conservation status and management needs. Thirty-five bird species have been observed on Lehua since 1931, including 18 seabirds endemic or indigenous to the Hawaiian Islands, one resident indigenous waterbird, six migratory waterbirds, and 10 alien land birds. We observed 29 of these species during surveys from 2002 to 2005, 13 of which had not been recorded on the islet previously. Over 25,000 pairs of eight seabird species were documented to breed on Lehua, including previously unknown breeding colonies of Black-footed Albatross (Phoebastria nigripes) and Laysan Albatross (P. immutabilis), and the largest breeding colonies of Brown Booby (Sula leucogaster) and Red-footed Booby (S. sula) in the Hawaiian Islands. Remains of a Newell’s Shearwater (Puffinus auricularis newelli) chick and a Band-rumped Storm-Petrel (Oceanodroma castro) chick were found, demonstrating that those species have nested on the islet and probably still do. The nesting season varied among species, with most species breeding from March to August, and at least one species breeding in every month. Predation by alien Polynesian rats (Rattus exulans) and Barn Owls (Tyto alba) is the most serious threat to nesting seabirds on Lehua. Sediment beneath a Barn Owl roost contained hundreds of bones from a variety of bird species, including Brown Noddy (Anous stolidus), which has been extirpated from the islet. Feral rabbits (Oryctolagus cuniculus) are suppressing vegetation that could provide additional nest sites for Red-footed Boobies and help prevent erosion and burying of seabird burrows. The most urgent management needs on Lehua are eradication of alien Polynesian rats, alien Barn Owls, and feral rabbits. Rocky offshore islets like Lehua may become increasingly important in seabird conservation because their small size makes it more feasible to manage threats, and because they are less likely to be affected by increases in sea level associated with climate change.