Birdsong as an Indicator of Habitat Structure and Quality.

Birdsong is a complex and highly flexible sexual signal that plays a crucial role in intra- and intersexual communication. Various aspects of the surrounding habitat can influence birdsong; for example, birds may modify their songs to enhance acoustic transmission, or males in high-quality territories with abundant food resources may produce more elaborated songs. However, these mechanisms remain largely unexplored in many natural systems. In our field study, we recorded the songs of male-collared flycatchers () in a Hungarian population, alongside detailed habitat variables reflecting structure and quality. We analysed song traits describing frequency, temporal structure and complexity. Habitat variables included canopy closure, Shannon diversity index of the tree species, mean trunk circumference of dominant tree species and tree health status. We revealed that mean song frequency was negatively associated with canopy closure. This result likely reflects birds adjusting the frequency of their songs to the acoustic properties of their environment, or it may be explained by quality-dependent territory selection or the use of high-performance songs to signal territory quality. Our results have implications for the study of sexual selection and how birds adapt to different environments and suggest that aspects of birdsong can reflect habitat quality.