Spatial pattern of syllable sharing in white-throated thrushes: implications for song learning and dispersal behaviours

Abstract

The relationship between song sharing among male songbirds and geographic distance between their territories is a function of juvenile dispersal distance and length of the song learning period. I analysed the spatial pattern of syllable sharing in white-throated thrushes (Turdus assimilis) to infer their song learning strategy. Songs of 23 males from three different sites (2.5–21 km) in Puntarenas, Costa Rica, were studied using visual classification, spectrogram correlation and multidimensional scaling analysis. In total, 8505 syllables were classified into 296 syllable types. All males shared syllables but most types were unique to particular males, suggesting that males invent most of their repertoires. Repertoire dissimilarity increased with geographic distance. Within sites, syllable sharing was higher between intermediate than between adjacent neighbours. These results suggest that juvenile dispersal distance is <2.5 km and relatively lower song sharing between adjacent neighbours may result from non-random dispersal or active avoidance by open-ended learners.