Quantitative analysis of differences in the vocaIizations of the Common Swift Apus apus and the Pallid Swift Apus pallidus

Malacarne G., Palomba I., Griffa M., Castellano S. & Cucco M.

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Multivariate analysis was used to assess acoustic features of the vocalizations of the Common and Pallid Swifts. One set of features, consisting of frequency and temporal patterns, set the two species quite apart. Previous differences based on subjective evaluations have been specified: Pallid Swift calls are on a lower frequency, especially the final part of the vocalization. This difference is discussed considering the features of Swift environment, However, we have no conclusive evidence as to whether these differences play a role in reproductive isolation between the two species.