Response of the emerald-spotted wood-dove to the song of conspecific males and sympatric congeners

Bird song contains crucial information that enables recognition of conspecific individuals from a distance, which facilitates subsequent complex behaviors related to mate attraction and rival deterrence. Loud broadcast signals of non-learning bird species are usually treated as less complex than songs of Oscines, but several studies have revealed that song learning is not necessary for the evolution of complex signaling. Here, we focused on a species of African wood-dove which produces superficially simple songs consisting of short notes organized into two parts of different amplitude. Our model was a population of emerald-spotted wood-doves (Turtur chalcospilos) that live in the same area as the physically and vocally similar blue-spotted wood-dove (Turtur afer). We tested the responses of male emerald-spotted wood-doves to different playbacks simulating territorial intrusion. We used songs of the focal species and of the congener, two types of artificially mixed songs with different parts belonging to the focal or congeneric species, and a control song. We aimed to assess (i) whether the focal species responds only to its own species' song or exhibits interspecific territoriality, and (ii) which part of the song is responsible for coding species identity. We found that male emerald-spotted wood-doves responded strongly to playback, but almost exclusively approached only the playback of their own species' song. Additionally, only conspecific song caused a decrease in song rate during playback and an increase in song output after playback. Our results suggest that emerald-spotted wood-doves are able to discriminate their own songs from those of congeners and do not exhibit interspecies territoriality. We were unable to identify a single part of the song that codes species-specificity, as mixed songs of any kind did not substantially increase responsiveness to playback in comparison to the congener song or the control. We discuss these results in the context of current hypotheses regarding interspecific territoriality and the evolution of species-identity coding.