Song theme sharing in the Grey-crowned Warbler, Phylloscopus tephrocephalus

In many songbird species, individuals sing multiple song types, some of which are shared between neighbours. Individuals may also share transitions between different song types, which leads to sharing sequencies of several (usually few) song types. Song themes, i.e. groups of song types that are consistently delivered in close succession, were identified in song sequences of several bird species. Detailed data on song theme sharing are still lacking. Here, we examined patterns of repertoire sharing in the Grey-crowned Warbler Phylloscopus tephrocephalus. Males of this species had repertoires of 29–42 song types that were divided into shorter song themes of up to 10–15 song types each. Each of the 13 studied males shared 81.6–100% of his repertoire as well as several song themes with other males. These themes recombined in different ways leading to the fact that exact song sequencing varied between individuals. That is why males shared much less transition types than song types in our study. Therefore, the analysis of song theme sharing may provide more careful description of sharing above the level of song type than the analysis of song sequence sharing alone.