Responses of Hermit Thrush (Catharus guttatus) males to conspecific playback with typical and atypical syntactical patterns.

Birdsong exhibits syntactical patterns, wherein singers from a variety of species perform vocal sequences that follow set rules with respect to the order of vocal units (e.g., song types or syllables). However, little is known with certainty regarding the degree to which such patterns contribute to the two main functions of birdsong, mate attraction and territorial defense. The present study investigates the role of syntactical patterns in the songs of the hermit Hermit Thrush (Catharus guttatus), which delivers its song types in a semi-predictable order that cycles up and down the frequency spectrum. A within-subjects playback experiment was conducted to assess the strength of territorial response among males exposed to conspecific song stimuli with and without species-typical patterns. The magnitude of territorial response did not differ with between the two stimulus types, suggesting that the syntactical patterns within Hermit Thrush song do not contribute to territorial defense and aggression. Implications for overall understanding of birdsong syntax, as well as future studies with this species, are discussed.