Close Males Sing With Dissimilar Minimum Frequency and Repertoire Size in a Wild Passerine

The position occupied in social networks influences the success of individuals in many animal species. However, the associations between bird song (an important means of communication) and the relative position in social networks remained understudied. Such associations are expected because neighbors can learn song elements from each other or change their songs due to competition, and also because song can be related to other individual traits determining social network positions. We investigated these phenomena in males of the collared flycatcher (<i>Ficedula albicollis</i>), a passerine with complex songs and intense territorial interactions. Relying on 19 years of song recordings, we used multiple traits reflecting the spectral and temporal characteristics and complexity of songs, as well as syllable composition, to investigate if similarity in song is associated with the position in neighbor networks. We also examined whether birds settle down in an age-dependent manner (as age is linked to individual quality) and whether the nonrandom spatial distribution of song is affected by the proportion of immigrants, young birds, or the number of displaying males. We found that the minimum frequency and the repertoire size of neighbors differed, but this pattern was not shaped by the investigated predictors. Therefore, our results highlight the need to study communication traits and social environment together. The fact that neighboring males tend to sing differently with respect to some song traits suggests that songs can be flexibly adjusted based on the performance of conspecifics.