Vocal interactions in nightingales, Luscinia megarhynchos: more aggressive males have higher pairing success

Song overlapping in birds is used and perceived as a signal of aggression, and evidence suggests that eavesdropping females base their extrapair mating decisions on the performance of males in vocal contests. In our study population of nightingales a large proportion of territorial males remain unpaired throughout the breeding season. A comparison between subsequently mated males and unpaired males may reveal whether females could use singing performance during vocal interactions in their choice of a social mate. We investigated how males that differed in their subsequent pairing status overlapped a noninteractive playback during the period of mate attraction, and how males used specific structural song components in response to playback. Subsequently mated males overlapped more playback songs than did males that remained unpaired throughout the breeding season. Males also adjusted the use of specific song components and decreased song rate during playback, suggesting that the flexible use of structural song components is more important in vocal contests than increasing song output. Because song overlapping is thought to be a signal of aggression, more aggressive males seem to have greater pairing success.