The demographic drivers of cultural evolution in bird song.

Social learning can give rise to shared behavioral patterns that persist as culture within animal communities, such as bird and whale songs and cetacean feeding techniques. These cultural traits evolve and can impact individual survival, population structure, and conservation efforts. Although theoretical work indicates that demographic processes-like population turnover, immigration, and age structure-significantly influence cultural evolution, empirical evidence from natural populations is limited. Using deep metric learning to analyze over 100,000 songs from >400 repertoires in great tits (Parus major), we show that demographic variation affects vocal cultures within the small spatial and temporal scales where learning occurs. Within-population dispersal homogenizes song culture, and immigrant birds adopt local songs while increasing neighborhood diversity through larger repertoires. Birds of similar age tend to have more similar repertoires, which provides evidence of cultural change, with mixed-age neighborhoods showing higher cultural diversity. We estimate that individual turnover is a main driver of cultural change and that its pace is also moderated by dispersal, immigration, and population age structure. These findings support theoretical expectations regarding a key role of demographic processes in cultural evolution while highlighting their interaction with species-specific factors such as the timing and mode of song acquisition.