Hakalau Bioacoustic Surveys and Models 2015

In this study, we create and evaluate a protocol to estimate the density, which can be used to estimate the abundance of terrestrial sound-producing animals from single automatic sound recorders. The protocol uses cue rates from the target species as well as sampling conditions and an estimate of the distance of the individual to the recorder based on the power of the sound. We applied our protocol to estimate the density of two Hawaiian forest bird species (Hawai'i 'amakihi, Chlorodrepanis virens and 'oma'o, Myadestes obscurus) on the island of Hawai'i, USA. We validate our approach by comparing our density estimations with others calculated at the same stations using a traditional point-transect distance sampling method based on human observations. Both rain and wind affected the analyses and were included in the density estimation. In general, the density estimates based on acoustic signs were lower than those based on human-made surveys, but the estimates were relatively close, especially for one species, the 'oma'o, validating our protocol.