Historically, bird song has been regarded as a sex-specific signalling trait; males sing to attract females and females drive the evolution of signal exag- geration by preferring males with ever... Show moreHistorically, bird song has been regarded as a sex-specific signalling trait; males sing to attract females and females drive the evolution of signal exag- geration by preferring males with ever more complex songs. This view provides no functional role for female song. Historic geographical research biases generalized pronounced sex differences of phylogenetically derived northern temperate zone songbirds to all songbirds. However, we now know that female song is common and that both sexes probably sang in the ancestor of modern songbirds. This calls for research on adaptive expla- nations and mechanisms regulating female song, and a reassessment of questions and approaches to identify selection pressures driving song elab- oration in both sexes and subsequent loss of female song in some clades. In this short review and perspective we highlight newly emerging questions and propose a research framework to investigate female song and song sex differences across species. We encourage experimental tests of mechanism, ontogeny, and function integrated with comparative evolutionary analyses. Moreover, we discuss the wider implications of female bird song research for our understanding of male and female communication roles. Show less
Many mating signals consist of multimodal components that need decoding by several sensory modalities on the receiver’s side. For methodological and conceptual reasons, the communicative functions... Show moreMany mating signals consist of multimodal components that need decoding by several sensory modalities on the receiver’s side. For methodological and conceptual reasons, the communicative functions of these signals are often investigated only one at a time. Likewise, variation of single signal traits are frequently correlated by researchers with senders’ quality or receivers’ behavioural responses. Consequently, the two classic and still dominating hypotheses regarding the communicative meaning of multimodal mating signals postulate that different components either serve as back-up messages or provide multiple meanings. Here we discuss how this conceptual dichotomy might have hampered a more integrative, perception encompassing understanding of multimodal communication: neither the multiple message nor the back-up signal hypotheses address the possibility that multimodal signals are integrated neurally into one percept. Therefore when studying multimodal mating signals, we should be aware that multimodal signals can give rise to multimodal percepts, meaning that receivers can gain access to additional information inherent to only combined signal components (‘the whole is something different than the sum of its parts’). We review the evidence for the importance of multimodal percepts and outline potential avenues for discovery of multimodal percepts in animal communication. Show less
