Avian Abundances on Yap, Federated States of Micronesia, after Typhoon Sudall

Typhoons can add to chronic threats such as incremental habitat loss and pressure from feral predators to jeopardize the unique biodiversity of Pacific Ocean islands. Typhoon Sudall severely damaged Yap, Federated States of Micronesia, in April 2004. To establish an initial assessment of consequences of the typhoon for the avian community on this poorly studied island, we surveyed birds along line transects in mangroves, savannah, and forest on Yap during the last week of August 2004. We found all expected 22 resident species in abundances whose rank order was very similar to results from surveys in the early 1980s. Most-common species were White Tern, Plain White-eye, Micronesian Starling, Micronesian Myzomela, and Yap Monarch. All five species were common in all three major habitats, mangroves, upland forest, and savannah, although terns nested primarily in forests. Least commonly encountered resident species were Common Cicadabird, Micronesian Pigeon, and White-throated Ground-Dove. We found one to six individuals of each of those species. We also encountered 27 species of migratory birds, including the first record for Yap of Greater Scaup. Populations of birds appeared to be about 50% lower across all resident species than estimates from 1983–1984, suggesting the possibility that Typhoon Sudall caused widespread mortality. However, other possible explanations for reduced abundances exist, which we review briefly. A long-term monitoring plan is needed to track population dynamics of birds on Yap.