The Avifauna of Kosrae, Micronesia: History, Status, and Taxonomy

Kosrae, the easternmost high island of Micronesia, is a 110 km(2) volcanic island rising up to 630 in above sea level. It is seldom visited by birders and ornithologists because it is small, isolated, and lacks any previously recognized extant endemic bird species. We review the history of research on the island's avifauna and summarize the status of each species, including documentation for six new species': Northern Pintail (Anus acuta), Gray Plover (Pluyialis squatarola), Common Snipe (Gallinago gallinago), Bristle-thighed Curlew (Numenius tahitiensis), Red-necked Stint (Calidris ruficollis), and Whiskered Tern (Chlidonias by-brida). We discuss previously undescribed vocalizations of endemic taxa and provide online reference to recordings. We also present supporting evidence for the recognition of two taxa as full biological species: Kosrae Fruit Dove (Ptilinopus hernsheimi; formerly part of the P. porphyraceus complex) and Kosrae White-eye (Zosterops cinereas, as a split from Gray-brown White-eye, Z. ponapensis). The avifauna of Kosrac includes 53 naturally occurring species of birds of which 13 breeding residents are extant (2 endemic species, 4 endemic subspecies) and 2 are extinct (both endemic species), 21 are boreal migrants from breeding populations in the temperate Northern :Hemisphere (including 11 exclusively Palearctic migrants and 3 exclusively Nearctic migrants), 5 are austral migrants from breeding populations in the temperate Southern Hemisphere, and 12 are visitors from breeding populations on tropical islands elsewhere in the Pacific. Two additional species have been introduced; one has a self-sustaining feral population and the other is extirpated. Because of the island's low human population and relatively pristine environment, resident breeding birds are thriving with no serious threats to their survival at present, except for overhunting of the Micronesian Imperial Pigeon (Duatia occanica oceanica).