Drones and sound recorders increase the number of bird species identified: A combined surveys approach

Many studies have compared results from sound recordings and traditional point-count survey observer data when surveying avian communities. None have investigated the use of a moving sound recorder to replicate line-transect surveying. We conducted point-count surveys and line-transect surveys in four urban/peri-urban habitats in Darwin, tropical Australia, with stationary and moving sound recorders, respectively, to assess whether such a combination would result in more bird species being identified than with either technique alone. More bird species were identified using sound recordings than standard observer data. Further, the difference in the number of species identified between the observer and audio from point-count surveys was found to be significant with audio identification being more accurate; however, line-transect surveys showed no significant difference between the two identification methods. Overall, there was no statistical significance between using point-count surveys and line-transect surveys for total species identified. Linear mixed modelling found the interaction between habitat and survey type (point-count vs line-transect) was strongly significant, but not so that between habitat and survey method (sound recording vs human observation). Our results indicate that the integration of bioacoustic and drone technologies with traditional avian surveying techniques adds significant additional identifications when compiling a species list of an area.