Female birds of several species prefer to mate with males who can perform elaborate songs with lots of sound variation, hence the evolution of complex calls like those of the lyrebird. But what about species that sing simple songs? Are the females of those species simply not as choosy? Not so, according to a new study by Gonçalo Cardoso and Yang Hu. They studied several species of wood warblers, many of which sing songs consisting almost entirely of trills—simple repetitions of the same syllable. Those species that use mostly trills, the researchers found, tended to sing faster and modulate pitch more widely than the other species. Those warblers appear to use their simple songs to impress choosy ladies or to fight rivals, but they demonstrate their prowess with the quality of the performance, not the complexity of the song. “These simple songs are like a canvas on which vocal ability can be advertised and assessed easily,” Dr. Cardoso said. “It’s easier to identify the best athlete on a 100 meter run than on a gymnastics competition,” he analogizes. The study suggests that mate choice can cut in two opposing ways, driving complex songs in some species and simple ones in others. Listen to the warbler’s simple call here: http://www.allaboutbirds.org/guide/wilsons_warbler/id.
Gonçalo C. Cardoso and Yang Hu, “Birdsong Performance and the Evolution of Simple (Rather than Elaborate) Sexual Signals”