Song type and song type matching are important for joint territorial defense in a duetting songbird

Birds have a diverse acoustic communication system, with species specific repertoires facilitating more complex behaviors in terms of both within- and between-pair communications. Certain song types are produced for specific functions, such as aggressive encounters. In addition, song matching behaviors, whereby neighboring individuals match song types, can be used in aggressive interactions as a sophisticated acoustic behavior. In this study, we examined the functions of song types, in a duet context, of male yellow-breasted boubous (Laniarius atroflavus), an Afromontane bush-shrike with a vocal sexual dimorphism. We aimed at assessing whether, structurally, certain song types elicited a heightened reaction than others, and also whether song matching affected response behavior. A dual speaker playback procedure was performed for 18 pairs of boubous, each pair being exposed to duets with three different male song types. We found differences in response towards the different duet types bu...