Female song can be as long and complex as male song in wild House Finches (Haemorhous mexicanus)

In temperate zone avian species, female song is typically less common and structurally complex than male song. Although anecdotal accounts suggest that female House Finch (Haemorhous mexicanus) song is less complex, it has never been compared quantitatively with male song. We analyzed songs from 2 House Finch populations in southern New York to investigate the degree of sexual dimorphism in complexity, as measured by concavity, frequency excursion, and length of song. We found that, although females sing at a significantly higher mean frequency and lower bandwidth, there is no significant sex difference in the structural complexity of song. Future research should investigate whether female House Finch song has an unrecognized function, or whether the retention of complexity is a byproduct of selection on a correlated trait.