Tyrannidae is the largest family of birds, and its species breed throughout North and South America across broad climatic and ecological ranges. Across species, songs within the Tyrannidae family are highly variable, and as suboscine songbirds, their songs are innate, meaning that their songs are inherited rather than learned. Song variation among suboscine species therefore represents adaptive differences that may be associated with reproductive barriers. The overall goal of this study was to investigate how morphological, ecological, and geographic factors may have affected song evolution and ultimately whether song evolution is linked to the radiation of the Family Tyrannidae. To do this, we used phylogenetically controlled analyses to test the relative influence of morphology (body size, beak size), ecology (habitat, diet, climate) and range overlap on song evolution. Our results indicate that song structure in Tyrannidae appears to be driven by a combination of range overlap, selection on signaling via the environment as well as selection on morphological traits. Environmental properties seem to have the strongest effect on song length, while morphological properties appear to drive song frequency in tyranids. Understanding the ways in which differences in song between related species arise and the role of song divergence in species radiation is an important topic in evolutionary ecology because it addresses a fundamental question in biology—the origin of species.
