Passive Acoustic Monitoring (PAM) is emerging as a method to inexpensively and reliably collect information on bird species richness. Several studies have compared PAM to traditional methods of species enumeration and have found them to yield similar results. However, none of these studies has been conducted in an urban environment. The field of urban ornithology is rapidly expanding, and there is an urgent need for ecological best practices regarding biodiversity maintenance and improvement. PAM could prove to be a valuable data collection tool in this context, while also providing important acoustic data relevant to human well-being. However, urban environments present very different acoustic environments than natural areas, which affects both aural detectability of birds and their vocal behavior. Because of this, there is a need to evaluate PAM in urban settings. To test the suitability of PAM for biodiversity measurement in an urban environment, we paired point counts with acoustic recordings at six sites, ranging from front yards in areas of heavy residential development to natural fragments, all within an urban context. These sites were visited multiple times over the year, and recordings were later hand-identified and compared to the records of the human observers.
Results/Conclusions
Preliminary results suggest that more birds are detected by sight alone in residential sites compared to natural remnants. This suggests that PAM may be appropriate to measure biodiversity in these remnant habitats, but not in heavily developed settings. However, this is not due to acoustic masking, as these sites have similar acoustic profiles. Rather, birds in residential areas appear to vocalize less often than birds in natural remnants. This could be because birds are less likely to be defending territories in such heavily-disturbed sites. These findings suggest that PAM may be appropriate in more natural urban areas, but will underpredict biodiversity in built-up areas. Further work needs to evaluate how the potential increase in visual detectability resulting from a more open line of sight in built-up environments contributes to this effect.