Rainforest birds avoid biotic signal masking only in cases of high acoustic saturation.

Acoustic signaling among birds is central to intra-species communication, courtship, and reproductive success, and so habitat suitability is partially dependent upon the availability of a suitable acoustic niche. It is well documented that birds may modify their vocal behavior to avoid overlap with anthropogenic noise pollution, but responses to biotic signal making are less well understood. This study uses more than 50,000 h of audio recorded in tropical forest, and machine learning methods for the detection of the vocalizations of nine species of bird and tymbalizations of three species of cicada to examine patterns of signal masking and co-chorusing avoidance among species pairs. Among these focal species, no bird avoided co-chorusing with any other bird. Birds avoided co-chorusing with cicadas only and always when (1) the bird vocalized in a frequency band completely overlapped by the cicada tymbalization, and (2) the cicada tymbalization saturated the majority of that frequency band. These results indicate that avian behavioral modifications in response to biotic noise in longstanding species communities is similar to behavioral modifications observed in populations subjected to high levels of anthropogenic noise pollution—in all cases overlap avoidance is species-specific and dependent upon both frequency and intensity. [ABSTRACT FROM AUTHOR]