Signalling through acoustic windows: nightingales avoid interspecific competition by short-term adjustment of song timing

The function of bird song is closely linked to sexual selection through female choice and male-male competition, and thus variation in communication success is likely to have major fitness consequences for a singing male. A crucial constraint on signal transmission is imposed by background noise, which may include songs from other species. I investigated whether singing nightingales (Luscinia megarhynchos) avoid temporal overlap with the songs of other bird species in a playback experiment. I analysed the temporal song patterns of six males, each of which were exposed to songs of other species. The nightingales significantly avoided overlapping their songs with the playback songs, and started singing preferentially during the silent intervals between the heterospecific songs. This timing of song onset produced a greater variability in pause duration compared to the nightingales' undisturbed solo singing. These findings suggest that birds adjust their song timing to avoid acoustic interference on short temporal scales, and thus are able to improve the efficiency of acoustic communication in complex sonic environments. Moreover, the results indicate that temporal song patterns can be affected by the songs of other species, and thus such influences should be taken into account when studying bird song in the field.