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Perceptual salience of acoustic differences between conspecific and allospecific vocalizations in African collared-doves

In speciation events, species-distinct vocal signals can diverge acoustically in many ways. Signal receivers have to be able to distinguish conspecific from allospecific vocalizations, and the perceptual salience of acoustic features is therefore expected to be an important factor in the evolution of such vocalizations. We tested how dissimilar the species-identifying perch-coos of 12 closely related turtle-dove species (genus Streptopelia) are, as perceived by one of its members, S. roseogrisea. With operant, psychoacoustic methods we trained six doves to respond only to their conspecific coo. Responses to the perch-coos of the 12 other dove species were used as a measure of their perceptual similarity to conspecific perch-coos. Turtle-doves differentiated between the allospecific coos: some were perceived as more similar to their own species’ coo than others. With multiple regression analysis we identified three acoustic features that correlated with these differences in perceptual similarity: coo duration, minimum frequency and Wiener entropy. In contrast to findings in other bird species, duration was by far the most important feature in the discrimination between conspecific and allospecific vocalizations for S. roseogrisea. The results suggest that this is due not only to the coos of the various species differing in duration but also to a comparatively high perceptibility of the differences in duration.  2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.