A comparative analysis of sex differences in birdsong

Birdsong is often used as an animal model for human speech and language, because of the many similarities between them. The assumption that in songbirds generally only males produce learned vocalizations whereas in humans both sexes do was, on the other hand, considered to be an important difference. A recent study, however, demonstrated that this assumption probably reflects a geographical research bias towards temperate zones. Most species found in this region belong to the most recently evolved group of songbirds, the Passerida, in which female song is uncommon. The study shows that female song is widespread across the more basal, non-Passerida, groups. Only few studies so far have investigated how different or similar song produced by male and female birds in non-Passerida species is. To compare sex differences across many different species, one needs a song analysis method that is independent of singing style. The aim of this thesis was to devise such a method based in part on...Show moreBirdsong is often used as an animal model for human speech and language, because of the many similarities between them. The assumption that in songbirds generally only males produce learned vocalizations whereas in humans both sexes do was, on the other hand, considered to be an important difference. A recent study, however, demonstrated that this assumption probably reflects a geographical research bias towards temperate zones. Most species found in this region belong to the most recently evolved group of songbirds, the Passerida, in which female song is uncommon. The study shows that female song is widespread across the more basal, non-Passerida, groups. Only few studies so far have investigated how different or similar song produced by male and female birds in non-Passerida species is. To compare sex differences across many different species, one needs a song analysis method that is independent of singing style. The aim of this thesis was to devise such a method based in part on sex differences that have previously been reported in the literature. To test this method, it was used to investigate sex differences in the song of six non-Passerida songbird species. This song analysis showed that the method could indeed be used to analyze sex differences in birds with different singing styles, and sex differences in some parameters, such as spectral similarity and element versatility, were found. In future studies, this method can thus be used to investigate sex differences in more species from different phylogenetic groups which can help better understand the selection pressures that led to the sexual dimorphism in song that can currently be observed in Passerida songbirds. This insight can then be used to generate hypotheses about the evolution of sex differences in the learned vocalizations of other vocal learning species, such as humans.Show less

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A comparative analysis of sex differences in birdsong