biologically, having a large repertoire is advantageous in territorial defence and larger repertoires are also correlated with higher reproductive success. marcel lambrechts and andré dhondt proved that average strophe length and repertoire size can be used as proxies for male quality. male quality refers to the fitness of the bird, measuring how well it survives and its reproductive success. lambrechts and dhondt set out to find the answers to four questions also pertaining to percentage performance time and male quality in the great tit.