Song varies with latitude, climate, and species richness in a Neotropical bird

Animals can encode information within acoustic signals, particularly, bird songs can be remarkably complex and can indicate individual identity and quality. Two main sets of hypotheses attempt to explain the evolution of increased birdsong complexity across large-scale geographic ranges: (1) larger acoustic space availability, and (2) greater sexual selection intensity, both of which would favor the evolution of more complex songs at higher latitudes, more seasonal and/or species-poor environments. However, few studies have assessed patterns of song complexity for birds with broad geographic ranges. Here, we determined patterns of song variation in the blue-black grassquit (Volatinia jacarina), considering metrics of song complexity, structure and performance. This Neotropical bird occurs from Mexico to Argentina and produces a monosyllabic song. Using recordings from online databases, we calculated song metrics, such as bandwidth, song rate, number of song components, and proportion of...