Coding in the song of the wren: importance of rhythmicity, syntax and element structure.

Communication between territorial songbirds usually involves a transfer of encoded information over long distances. We would expect coding and decoding strategies to be adaptive given the constraints imposed by the habitat. We used playback to examine some song parameters important for information transfer in the wren, Troglodytes troglodytes. Six stimuli were tested with various modifications to song rhythmicity, song composition, element structure, syntax and overall song spectra. Song features encoding information essential for eliciting a territorial response seemed to be embedded in the fine structure of song elements, that is, their variations in frequency and amplitude over time. To function, this strategy must be flexible enough to accommodate the deleterious effects of habitat-induced degradation. All stimuli composed of original song elements elicited responses regardless of their other alterations. Rhythmicity seemed not to be essential for eliciting territorial behaviour. However, alterations in song rhythmicity, syntax and spectra affected territorial responses, suggesting that these nonessential song parameters do contribute to the options for discrimination. Copyright 2000 The Association for the Study of Animal Behaviour.