Geographic Variation of Song Sharing in Birds-A Meta-Analysis

Bird song plays a crucial role in sexual selection and often exhibits geographical variation, with neighboring birds typically singing more similar songs. Song sharing, created by birds learning songs or song elements from their neighbors or matching each other's song, is a key focus of research in this aspect. In this meta-analysis, we quantified the overall effect of geographic distance on song sharing and investigated the influence of migratory tendency, repertoire size, dichromatism (as a proxy for sexual selection intensity), and habitat (urban, rural, and natural) on the focal relationship. We confirmed that song sharing decreases with geographic distance but found no overall effect of migration or repertoire size. Interestingly, this association was stronger negatively in monochromatic species and suburban habitats, potentially indicating that dichromatic species prioritize individuality in their vocal displays, while suburban birds may benefit from increased song sharing to enhance signal transmission or reduce competition. Our findings emphasize the importance of considering multiple factors when studying geographical variation in bird song. Future research should investigate other measures of song similarity and the roles of social structure and learning mechanisms.