Temporal acoustic patterns in an old-growth emberá community forest in Darién, Panama. Do birds shape neotropical soundscapes?

Few habitats remain undisturbed by human impact. Even protected areas are vulnerable to noise pollution, for example from traffic or industrial activities, which can affect species composition, behavior and health as well as ecosystem processes. The forest of Tierras Colectivas Emberá de Balsas in Darien, Panama is one such acoustic sanctuary, a territory of ~125,000 ha covered by old-growth forest with high biodiversity. Collaborating with Emberá communities, we recorded soundscapes throughout the dry and wet seasons to characterize temporal patterns in these exceptional natural soundscapes. Studies from the tropics have shown that birds are sensitive to changes in land use and forest structure and fragmentation. We therefore investigated the effect of bird richness on the temporal patterns of several acoustic indices and identified the index that best reflected differences in bird richness. Between diel periods and seasons, we observed a significant temporal turnover of acoustic properties. This suggests that animals active during these periods share distinct acoustic properties, forming an acoustic guild. Acoustic indices are generally driven by dominating sound sources. Most bird species were vocally rare, yet differences in bird richness could explain a significant amount of variation in acoustic patterns. An even larger amount of deviance was explained by considering only vocally common species. The frequency range between 0.1 - 4 kHz was least occupied by other sound sources and very important for bird communication. This stresses the need to protect natural soundscapes from low-frequency noise caused by engines and conserve the last remaining acoustic sanctuaries. The Tierras Colectivas Embera de Balsas constitute such an acoustic sanctuary.