Song degradation during propagation: importance of song posts and reaction to degraded signal in the wren Troglodytes troglodytes [abstract]

Degradation of the wren song was investigated by analysing sound attenuation, duration of notes and silences, spectrum composition, modifications of frequency modulated notes and amplitude fluctuations. All these parameters are affected by propagation. It appears that the choice of an elevated song post improves the reliability of all song parameters and increases the propagation distance of the song. It also improves the wren's ability to hear an opponent's song. Following this analytic work, we investigated the response of the wren to a degraded song. The propagated song is still considered by the receiver as a specific territorial aggressive signal. However, it appears that the wren is sensitive to song degradation, since the territorial reaction is modified when the rival song has been degraded during propagation. Especially, it chooses a higher song post than when it responds to an undegraded song. Taking into account the previous results concerning song degradation, this behavioural change may correspond to a long distance communication strategy. As the acoustic information is perturbed, the wren perches itself to improve the reception of its rival song and/or the reliability of the propagation of its own territorial song.