Acoustic monitoring of the great reed warbler using multiple microphone arrays and robot audition

This paper reports the results of our field test of HARKBird, a portable system that consists of robot audition, a laptop PC, and omnidirectional microphone arrays. We assessed its localization accuracy to monitor songs of the great reed warbler (Acrocephalus arundinaceus) in time and two-dimensional space by comparing locational and temporal data collected by human observers and HARKBird. Our analysis revealed that stationarity of the singing individual affected the spatial accuracy. Temporally, HARKBird successfully captured the exact song duration in seconds, which cannot be easily achieved by human observers. The data derived from HARKBird suggest that one of the warbler males dominated the sound space. Given the assumption that the cost of the singing activity is represented by song duration in relation to the total recording session, this particular male paid a higher cost of singing, possibly to win the territory of best quality. Overall, this study demonstrated the high potential of HARKBird as an effective alternative to the point count method to survey bird songs in the field.