A Sexually Dimorphic Learned Birdsong in the Northern Cardinal

Abstract

In most temperate zone songbirds, singing is solely a behavior of males. However, in some species, such as the Northern Cardinal (Cardinalis cardinalis), both sexes sing, and in both, songs are learned. The song of male and female cardinals sounds very similar to the human ear. Whether songs learned by the two sexes can be sexually dimorphic in acoustic structure has never been examined. In the present study, I carried out detailed analyses of the acoustic structure of male and female songs. Songs of the two sexes proved to be dimorphic with respect to the degree of syllable stereotypy and the amplitude of harmonics. These findings show that vocalizations that are learned by the two sexes can be sexually dimorphic.