Song complexity and song structure in the Moustached Warbler Acrocephalus melanopogon

We examined different song parameters leading to a complex song configurati on, and song output (production), and their relation in male Moustached War blers and discuss them with reference to female choice. With more than 120 different syllables per two minutes of song, male Moustached Warblers can b e regarded as one of the most complex singers within the genus Acrocephalus . We found significant differences between males for almost all song parame ters investigated (repertoire size, switching and repetition rate, song spe ed and strophe length) but not for time spent singing per 20 minutes. This individual variation probably is an important cue for female mate choice. M ale Moustached Warblers achieve song complexity mainly via frequent syllabl e switching. Song complexity seems to be consistent throughout the song and our results suggest that females could assess the overall song complexity of a singer by examining even very short song bouts. Furthermore, a high pr oportion of motifs - clusters of syllables with the same sequence - occurs within the song of each male which would also Facilitate assessment of song complexity by females. However, repertoire size and strophe length were po sitively related, thus it remains to be investigated which song feature, if any, females actually use.