Data from: Female song is widespread and ancestral in songbirds

Bird song has historically been considered an almost exclusively male
trait, an observation fundamental to the formulation of Darwin’s theory of
sexual selection. Like other male ornaments, song is used by male
songbirds to attract females and compete with rivals. Thus, bird song has
become a textbook example of the power of sexual selection to lead to
extreme neurological and behavioural sex differences. Here we present an
extensive survey and ancestral state reconstruction of female song across
songbirds showing that female song is present in 71% of surveyed species
including 32 families, and that females sang in the common ancestor of
modern songbirds. Our results reverse classical assumptions about the
evolution of song and sex differences in birds. The challenge now is to
identify whether sexual selection alone or broader processes, such as
social or natural selection, best explain the evolution of elaborate
traits in both sexes.