Editorial: Fitness Costs and Benefits of Female Song

The complexity and musicality of birdsong has fascinated naturalists for centuries. However, the historical research focus on temperate northern hemisphere birds has led to a widespread perception that song production is the domain of males alone. More recently, studies of birdsong have undergone a major paradigm shift, with the discovery that song in female birds is in fact widespread and ancestral, occurring in over 70% of surveyed species (Odom et al., 2014). This revolution in our understanding of song evolution has significant implications. First, it casts doubt on the view that song evolved primarily through sexual selection acting on males. Instead, the discovery that song occurred ancestrally in both sexes raises the possibility that song evolved initially for broader, social functions. Second, where sexual dimorphism in song production occurs, it is likely to reflect relatively recent loss of female song from an ancestor that had both male and female song (Odom et al., 2014). This shifts the focus of questions about sexual dimorphism in song production from “why do males sing?” to “why have females of some species lost song?.” These issues are addressed in this Research Topic by Price, who argues that recent findings about the prevalence of female song do not conflict with previous research, but instead highlight some problematic assumptions about the evolution of sexual dimorphisms. These include misconceptions that current patterns of elaboration and diversity in each sex reflect past rates of change and that levels of sexual dimorphism necessarily reflect levels of sexual selection. Given the changing focus in studies of birdsong evolution, a better understanding of how selection acts on song in females is sorely needed. Specifically, we need to understand the fitness costs and benefits of female song, yet there is an almost complete dearth of studies on this topic. The contributions presented in this special issue approach this topic from a diversity of angles, encompassing measures of the relationship between song and fitness, between song and other display traits and between male and female songs, as well as investigations of how females learn their songs.