Research on avian vocalisations has traditionally focused on male song produced by oscine passerines. However, accumulating evidence indicates that complex vocalisations can readily evolve outside the traditional contexts of mate attraction and territory defence by male birds, and yet the previous bias towards male song has shaped – and continues to shape – our understanding of avian communication as a whole. Accordingly, in this review we seek to address this imbalance by synthesising studies on female vocalisations from across signalling contexts throughout the Aves, and discuss the implications of recent empirical advances for our understanding of vocalisations in both sexes. This review reveals great structural and functional diversity among female vocalisations and highlights the important roles that vocalisations can play in mediating female‐specific behaviours. However, fundamental gaps remain. While there are now several case studies that identify the function of female vocalisations, few quantify the associated fitness benefits. Additionally, very little is known about the role of vocal learning in the development of female vocalisations. Thus, there remains a pressing need to examine the function and development of all forms of vocalisations in female birds. In the light of what we now know about the functions and mechanisms of female vocalisations, we suggest that conventional male‐biased definitions of songs and calls are inadequate for furthering our understanding of avian vocal communication more generally. Therefore, we propose two simple alternatives, both emancipated from the sex of the singer. The first distinguishes song from calls functionally as a sexually selected vocal signal, whilst the second distinguishes them mechanistically in terms of their underlying neurological processes. It is clear that more investigations are needed into the ultimate and proximate causes of female vocalisations; however, these are essential if we are to develop a holistic epistemology of avian vocal communication in both sexes, across ecological contexts and taxonomic divides.
Reproductive suppression, whereby individuals decrease the reproductive output of conspecific rivals, is well-studied in mammals, but while it is suspected to be widespread in birds, evidence of this phenomenon remains rare in this class. Here we provide compelling evidence of reproductive suppression in the Superb Lyrebird (Menura novaehollandie), with the first audio-visual documentation of the destruction of one female’s nest by another. We propose that nest destruction may be a strategy that females use in protracted territorial negotiations spanning multiple breeding seasons, and discuss how reproductive suppression could explain puzzling nesting behaviours in this species, such as the construction of multiple unfinished nests in each breeding season. More broadly, these results reveal high intra-sexual competition among female lyrebirds, and thus may provide an explanation for their elaborate vocal displays.
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