Are different song types used in different contexts in brownish-flanked bush warblers?

The repertoires of most songbirds consist of two or more different song types. Studies on a growing number of species have indicated that song types are used selectively in different contexts. For example, two bush warblers (Cettia diphone and C. cettia) use song types selectively in spontaneous singing and playback-evoked singing. Most male brownish-flanked bush warblers (C. fortipes) have two distinct song types. In this study, we tested whether these two song types are used selectively in different contexts. Most frequency and temporal variables are significantly different between these two song types, but neither song type is used more frequently during or after playback compared to spontaneous singing. Additionally, males did not respond differently to the two song types during playback experiments. In conclusion, these two song types differ significantly in both frequency and temporal variables, but we did not find any evidence that they are used selectively in different contexts. Comparing two related bush warblers (C. diphone and C. cettia) that selectively use different song types in different contexts, our study offers further evidence that avian vocalization is a plastic characteristic and can vary considerably, even among closely related species.