Figure 1.

Sonograms illustrating variation in the structural complexity of song playbacks and the acoustic make-up of noise treatments. (a) Structural differences between a low and high complexity song playback (xenocanto.org; respective identifiers: XC349141, XC414220), where higher complexity is characterized by longer duration and by greater syllable abundance, diversity (discrete syllable types are denoted by separate letters) and versatility (unique syllable transitions). (b) Noise treatments exhibited spectral overlap with lower frequency elements of songs.