Bird song is thought to be subject of both inter- and intra-sexual selection and song complexity a signal of
male quality. One aspect of song complexity, repertoire size, correlates with estimates of male quality in
several passerine species. 
The Common Blackbird (Turdus merula) has a large repertoire of different song patterns which are
organized in a complex structure without fixed song types. Previous studies found that Blackbirds show
large individual differences in repertoire sizes and use these repertoires in both inter- and intra-sexual
contexts. In this study we investigate the signal value of repertoire size in Blackbirds in an intra-sexual
context with the hypothesis, that males use the repertoire sizes of rivals as a cue to assess their quality. We
conducted playback experiments in which we broadcast songs of conspecifics with different repertoire
sizes to the test birds. The responses will be discussed in relation to the test birds own repertoire sizes.