Status of Landbirds in the National Park of American Samoa1

Abstract

Abstract: The National Park of American Samoa (NPSA) was surveyed in 2011 and 2018 using point-transect distance sampling to estimate trends in landbird distribution, composition, population density, and abundance. Surveys were conducted within the Ta‘ū Unit and Tutuila Unit, each on separate islands of American Samoa. We detected a total of 14 species during surveys and there were sufficient detections of seven species to allow for density estimation and abundance within each unit. We assessed differences in density between surveys with a two-sample z-test and found significant declines of Blue-crowned Lorikeets (Vini australis) in the Ta‘ū Unit, and of Samoan Starlings (Aplonis atrifusca) in the Tutuila Unit. Density estimates of the Crimson-crowned Fruit Dove (Ptilinopus porphyraceus), Pacific Kingfisher (Todiramphus sacer), Polynesian Wattled Honeyeater (Foulehaio carunculatus), and Samoan Starling (in the Ta‘ū Unit) were also lower in 2018 than 2011, but differences were inconclusive because of relatively large variance estimates. Densities of the Polynesian Starling (Aplonis tabuensis) and Pacific Imperial Pigeon (Ducula pacifica) in the Ta‘ū Unit were higher in 2018 than 2011, but differences were similarly inconclusive. Lower 2018 densities could be due to Tropical Cyclone Gita that struck the islands just four months before the surveys. We provide indices of relative occurrence and abundance for the remaining seven species detected, which include the Many-colored Fruit Dove (Ptilinopus perousii) and the rarely detected Spotless Crake (Zapornia tabuensis)—both of which are species of concern in American Samoa.