Data for: Geographic variation of song sharing in birds - a meta-analysis

Bird song, an important signal in sexual selection, often displays geographical variation as closer birds usually sing more similar songs that can lead eventually to speciation. Song sharing is a commonly investigated trait in this aspect that is created by neighbouring birds learning songs or song elements from their neighbours or matching each other’s song.
However, the generality of this phenomenon and the factors and mechanisms that shape it are not fully discovered.
In this meta-analysis, we investigated the overall relationship between song sharing and geographical distance and the effect of some variables with potential effect: migratory tendency, song complexity, dichromatism (as a proxy for the strength of sexual selection) and habitat (urban, rural or natural).
We found a general pattern of more shared songs in closer birds, but no comprehensive effect of migratory status or song complexity.
However, the general pattern were stronger in monochromatic birds and in suburban habitats, suggesting that dichromatic species may share fewer songs with their neighbours to advertise their individuality for potential mates and more urbanized areas my necessitate more song sharing to produce vocalizations spreading efficiently under these conditions or due to increased competition.
Our results highlight the need to study multiple potential creating forces when investigating geographical variation in song sharing.
Further research should explore also the patterns in other types of song similarity measures and the effect of social structure and learning.