Singing complexity of the banded wren (Thryothorus pleurostictus): Do switching rate and song-type diversity send different messages?

摘要

Most species of songbird possess repertoires of song types or variations that allow singers to vary how they present their songs. "Complexity," or the amount of variation in a singing performance, has several distinct components that include the number of song types used, variation within song types, and rate of switching between song types. Because singers can control each factor somewhat independently, different components may encode different kinds of information. In a series of interactive playbacks, I presented Banded Wrens (Thryothorus pleurostictus) with stimuli that altered song-type diversity and switching rates independently. My results show that switching rates affect males' aggressive approach responses, with lower switching rates eliciting stronger responses. By contrast, song-type diversity does not appear to affect males' approach responses when switching rates are held at a high and constant level. Although focal male switching rates and song-type diversity are not strongly influenced by playback type, males frequently respond to high-diversity playback with delayed matches. Delayed matching entails using one or more of the same song types from the playback, without immediate song-type matching. Although delayed matches occurred at levels above chance during high-diversity playbacks, focal males appeared to avoid them during other types of playback; immediate matches were rare and repertoire matches frequent for all playback treatments. Overall, males' responses to the three playback stimuli suggest that switching rate and song-type diversity encode different messages.