The degradation of bird sounds during long-range propagation depends on different parameters such as density of vegetation, height from the ground and atmospheric perturbations. We investigated whether the wren Troglodytes troglodytes, a bird species which has a high-pitched song that is very susceptible to degradation and lives in an environment that is very restricting for sound propagation, has any advantage in choosing relatively high song posts. Song degradation was investigated by analysing sound attenuation, duration of notes and silences, spectrum composition, modifications of frequency-modulated notes and amplitude fluctuations.
Our data show 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 male wren's ability to hear opponent songs. The results are discussed from an ecological point of view.