A comparative study of song form and duetting in neotropical <em>Thryothorus</em> wrens

The traditionally-defined wren genus Thryothorus is notable for its diversity of singing styles with some species producing highly coordinated duets or choruses in various formats while, at the other extreme, songs are performed almost exclusively by males. In this comparative study, we document the singing styles of almost all of the 27 or so species in this group, relating these to a molecular phylogeny in an effort to identify the conditions that have led to the evolution of duetting and chorus singing. In a previous study, we used molecular data to demonstrate that Thryothorus is actually paraphyletic, leading us to propose its splitting into three genera ( one newly described) in addition to Thryothorus. Here we show that most species within each of these four genera usually sing with the same style, and that these styles tend to differ between the genera. We also show that a few species have songs that differ markedly from those most typical of their genus. We argue that these exceptional cases will provide important insights into the origins of duetting behavior, and tentatively suggest factors that may have played a role in determining the extent to which male and female birds combine their vocalizations together.