A review of the literature on female birdsong function

Growing research on the function of female birdsong now allows for identification of large-scale patterns emerging in the published literature. We conducted a review that analysed female birdsong function studies to characterize the literature and research approaches in this field. We examined when, where and how researchers study female birdsong function and then quantified which functions for female song were most often supported by authors. Our data set included studies published between 1900 and 2022 that concentrated on singing female birds and either investigated or addressed functions of solo female song directly. The number of female song studies published per year has increased rapidly in recent decades, with the majority of the work focused on North/Central American species, followed by Australian and South American species. Most research studies used natural observation techniques, about half used playback and only 21% used other manipulations. In 67% of the studies analysed, female song was reported to be used in defence of a territory, 43% of studies reported intrasexual competition/aggression and 45% reported intrapair communication. Mate attraction and parent–offspring communication were the song functions least often supported and least often tested by authors. Most authors identified multiple contexts in which female song functioned in each study species. Outcomes match the demonstrated multifunctionality of male birdsong. In contrast, females apparently use song for mate attraction much less than male birds do. Surprisingly, less than 10% of papers directly linked female song behaviour to reproductive success, a connection providing critical support for ultimate explanations of function. It is evident that scientific interest in female birdsong function is on the rise. Our review identified a need for future research to include African and Asian avian species and studies that comprehensively test the fitness correlates of female birdsong function.