Invasive species eradication and control are considered vital components of the conservation, restoration, and management of many native ecosystems. Invasive ants, which are notoriously difficult to eradicate, can cause catastrophic changes in ecosystems and are aggressive colonists. Here we report the eradication and control of two widely distributed invasive ants and subsequent unanticipated effects on arthropod and avian communities. We used a paired experimental design that included 1 year of baseline data collection, to test the effects of the formicide hydramethylnon on abundances of two ant species on two pairs of offshore islets. Pheidole megacephala was eradicated from the treated islet in pair 1 and was not detected during 2003-2008. On pair 2 Solenopsis geminata numbers declined, but the species remained present. Target ant densities remained high on untreated islets. Application of hydramethylnon reduced numbers of alien cockroaches (Order: Blattaria), but we did not detect effects on other nontarget arthropods. The eradication of P. megacephala was followed by dynamic compositional changes in the ant community, including the apparent colonization by three species (S. geminata, Tetramorium bicarinatum and Anoplolepis gracilipes) previously undetected on the islet. One of these, A. gracilipes, underwent a rapid range expansion during 2006-2008 which corresponded with reduced seabird nesting success. We conclude that hydramethylnon can be used effectively to eradicate P. megacephala. However, ant eradications can have detrimental effects on ecosystems and the potential for subsequent colonization of sites by other ant species that may be more harmful and more difficult to eradicate needs to be considered.

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,