The Moustached Wren Thryothorus genibarbis is a common South American species found at forest edges and singing either in solo or duet. In the duet song the Notes are alternated by males and females in highly synchronized patterns. We analysed the repertoire of eight pairs of T. genibarbis from a population in Santa Bárbara, 50 km from Belém, PA, Brazil. We identified two different duets and three solo phrase types, one of which (“introductory phrase”) is emitted also at the beginning of the duets. This phrase is made of three Notes of two types (ABB) and was present in all the songs of the observed pairs. The duets had the same syntax, one type showing the note sequence ABB CD ABB CD ABB, and the other the alternative CD ABB CD ABB; according to our observations the first duet type is started by the male and the second by the female. These four note types (A to D) differ between the pairs, but some note sharing occurs between neighbours. The other solo vocalizations are variable among the pairs in note types, sequence and number of Notes. Playback experiments show that one of the solo vocalizations has an alarm function, while duets and the other solo phrases are related to territorial defence. These results indicate that the song syntax of the duets is a species-specific parameter, although other parameters, like the minimum frequency of the Notes, are also stereotyped. The maximum frequency of the Notes and the note shapes are variable among the pairs and these parameters could be used for individual recognition.
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