Territorial song frequency does not signal body size in a song-learning passerine.

The negative relationship between song frequency and body size in birds is well-established across species. However, whether song frequency reliably signals body size and individual quality requires more detailed within-species comparisons, particularly in species with diverse song repertoires. We investigated this relationship in the Ortolan Bunting (Emberiza hortulana), a song-learning species with a limited repertoire. Males of this species produce songs composed of two phrases: an initial phrase, which varies across individuals and defines their repertoire, and a final phrase, which is shared across the population. We analysed multiple frequency parameters across both components, accounting for phrase-sharing patterns among males, to assess whether song frequency reflects body size, using tarsus length as a proxy. No significant associations were found between body size and any frequency measure. These findings contribute to the ongoing debate over whether sound frequency signals body size, and by extension, competitive ability, during territorial interactions. Our results highlight the importance of within-species approaches and underscore the need to consider vocal learning dynamics, such as song sharing patterns, when exploring this relationship in song-learning species.