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Studies of auditory distance perception in song birds 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 can use reverberation and
high-frequency attenuation separately 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.
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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.
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