Résumé
Vocal dialects have been described in several taxa such as humans, cetaceans, bats and birds. They are characterized by geographic variation in vocal signals and can range from several hundred kilometres to less than two kilometres (micro-dialects). Most studies reported stronger responses by both males and females to local compared to foreign songs but up to date species with micro-dialects remain poorly studied. We studied a migratory population of a territorial songbird, the black redstart, in a French mountain village. Only males sing and they defend territories around farms and houses. The patchy distribution of the buildings leads to small neighbourhoods (2-8 males), with important song sharing between neighbours but low song sharing between different building patches (micro-dialects). We broadcast during the 2021 and 2022 breeding seasons (April-May) two non-familiar vocal stimuli: a song of the local micro-dialect and a song of a foreign micro-dialect. We hypothesized that birds’ territorial responses will be stronger towards the songs of the local micro-dialect. In line with our prediction males (n=26) spent more time near the loudspeaker and performed less flights over the speaker for the local song treatment.These results suggest that male black redstarts discriminate between local and foreign micro-dialects, consistently with the existing literature on species with broader dialects. Further studies are needed to understand the function of the micro-dialects in the black redstart and more broadly in songbirds.