Comparisons Between Autonomous Acoustic Recordings and Avian Point Counts in Open Woodland Savanna

In order to evaluate the possibility of using this method in the Brazilian Cerrado or other open vegetation areas, we compared the performance of point counts and autonomous recording units (ARU) for avian monitoring. From September to November 2012, we surveyed birds in 13 points established in six localities in central Brazil by using simultaneously ARU and point counts for species presence only comparisons. We identified a total of 84 species and found no significant differences between the number of species obtained by each method. Differing from what we initially expected, few records in point counts were obtained only by visual detection. The number of species registered by ARU corresponded to 90.4% of all observed species. About 92% of the recorded species sang at least once during point counts. Of all species recorded, 17% were not recorded by point counts and 10% were missed by ARU. Jaccard’s index of similarity was 68%. Our results indicate that the ARU can be an effective method to sample bird assemblages in open vegetation areas, such as the Brazilian Cerrado, being as efficient as the point count proceeding is. The disadvantages of ARU have already been highlighted in the literature (huge data volume to process, high costs to acquire the equipment, malfunctioning and loss, among others), but we must add that missing visual contacts with species must be considered depending of the study’s scope and the type of bird species in question. Nevertheless, the use of ARU can be a cost-effective method for long-term monitoring programs and also helps to quickly obtain the necessary data to characterize species assemblages associated with highly threatened ecosystems, such as the Brazilian Cerrado.