Song repertoire size is correlated with body measures and arrival date in common nightingales, Luscinia megarhynchos

In songbirds, the individual features of a male's song play a role in female choice and male–male interactions. Therefore, it has been hypothesized that the song characteristics of an individual should be correlated with its quality and this has been shown for some species. The species studied so far have only small or medium-sized song repertoires, leaving open the question of whether, in species with large repertoires, song characteristics such as repertoire size are related to male quality. We investigated the correlations between body measures, song characteristics and arrival dates of common nightingales, a songbird species in which males have extraordinarily large song type repertoires. We found that birds with large repertoires had longer wings and were heavier, and arrived earlier, than those with small repertoires. Other song characteristics, such as song diversity and proportion of whistle songs, were not significantly correlated with body measures. When we correlated body measures with arrival date, we found that birds that arrived earlier were heavier and tended to be in better condition. These findings provide supporting evidence that repertoire size is an indicator of a male's quality.