Forest degradation reduces acoustic partitioning in tropical avian communities

The acoustic niche hypothesis posits that species partition acoustic space by frequency and time to avoid signal masking, and that any local loss of species leaves detectable gaps in co‐evolved soundscapes. However, loss, fragmentation and disturbance of habitat often lead to species turnover, and as sensitive species are lost, generalist species colonise, potentially leading to novel overlaps of acoustic niches. We tested the acoustic niche hypothesis in variably disturbed tropical forests in the Brazilian Amazon by comparing overlapping vocalisations in undisturbed and disturbed forests. We measured the effect of disturbance on the frequency of overlapping vocalisations, then assigned sensitivity scores to each species and modelled how species sensitivity and species richness per sound file impacted overlapping vocalisations. We found that logged forests that have burnt recently had significantly higher rates of vocalisation overlap. Across all disturbance types, overlapping vocalisations were significantly higher when species richness and species sensitivity per 15‐s sound file increased. To our knowledge this is the first paper to test the acoustic niche hypothesis in human‐modified tropical forests and it provides insight into the impact of disturbance on species' ability to effectively communicate, as well as the utility of passive acoustic monitoring in measuring the responses of avian communities to global change.