Adaptive hypotheses on the evolution of non-vocal communication sounds in birds

Abstract

The birds have evolved to produce communication sounds(sonations) with their wings, tail, feet, or beak dozens ifnot hundreds of times independently. Ongoing workcontinues to uncover many new examples of sonationsand the physical acoustic mechanisms by which thesesounds are produced. The repeated (convergent)evolution of a trait permits sophisticated evolutionarytests of how and why it evolves. Here, we outline aseries of adaptive questions about the evolution ofsonations: Does producing sonations entail tradeoffswith other functions, such as flight? How do sonationsco-evolve with production of vocalizations? How dosonations co-evolve with behavior? Compared tovocalizations, do sonations occupy the same functionalspace as vocalizations? Do sonations occupy the sameacoustic space as vocalizations? Each of these questionshas already received some attention within individualbird clades, but with so many independent origins acrossbirds, the bigger picture has only begun to appear.