Secondary sexual characters may have evolved in part to signal resistance to parasites. Avian song has been hypothesized to be involved in this process, but the role of parasites in modulating acoustic communication systems in birds remains largely unknown, owing to lack of experiments. We...

Stress may have consequences for the evolution of condition-dependent sexual traits. For example, stress may be related to sexual traits through immune function, and sexual traits can reflect how individuals bear the costs of stress-mediated immunosuppression. However, male traits may be...