Auditory distance assessment of singing conspecifies in Carolina wrens: The role of reverberation and frequency-dependent attenuation

Studies of auditory distance perception in songbirds have shown that the overall degradation of songs during atmospheric propagation can be used to estimate the distance of the singer (called ranging). Natural sound degradation, however, incorporates several potential auditory distance cues that are not always equally available. This study investigated whether Carolina wrens, Thryothorus ludovicianus, can separately use reverberation and high-frequency attenuation to estimate the distance of a singer. In response to playbacks broadcast from within a subject's territory but at least 40 m away from its singing location, subjects approached more frequently and responded more intensely to playback of clear (unaltered) songs than to playback of reverberated, high-frequency attenuated, or naturally degraded songs. The results indicate that Carolina wrens can use reverberation and high-frequency attenuation separately to assess the distance of a singing conspecific. This ability could be an adaptation that enables them to defend territories efficiently in habitats with different acoustical properties. In addition, the ability to use several cues to assess auditory distance is likely to increase the accuracy of ranging by pooling information acquired in different ways.