A Comparison of the Structure of Acoustic Signals of Red-headed Buntings (Emberiza Melanocephala) and Black-headed Buntings (E. Bruniceps)

Analysis of song structure characteristics in the passeriform can be used as a powerful index in determining the taxonomical status of species of genus or subspecies of a species. Black-headed bunting (Emberiza melanocephala) and red-headed bunting (E. bruniceps) meet in a hybrid zone southeast of the Caspian Sea, Iran, and produce hybrid bunting individuals. This phenomenon, which creates these hybrid individuals may originate from the fact that there is a high similarity in the male song of the two species which may cause females to make a mistake in identifying the species they choose to mate with. This study was conducted to investigate the similarities and differences of the male songs of these two species by downloading their songs from the open-access online repository Xeno-Canto. Thirty audio files were selected for analysis in the warbleR software. The spectrograms and principal components were extracted according to the offered functions of this package. The Principal Component Analysis (PCA) showed no clustering of signals detected by this technique as well as overlap in some of the sound characteristics of the two species. The results of the present study revealed that despite the evolution of plumage and morphometric differences between the two species, the mechanism of reproductive isolation between them (including the development of acoustic signals to correctly identify males and females of each species and exclude other species individuals) was still incomplete which may cause gene flow and consequently hybridization.