A look into coastal Rufous-collared Sparrows vocalizations: do they modify their songs to reduce surf-noise masking?

LIJTMAER, DARÍO A.; TUBARO, PABLO L.; CANALE, ELISABET

Congreso; VII North American Ornithological Conference (virtual); 2020

American Ornithological Society y otras 6 sociedades de ornitología de América

Acoustic signal transmission is deeply intertwined with the surrounding environment and is constrained by noise. Birds have been shown to adjust their song amplitudes and frequencies, and also to use a repetitive and predictable structure, to avoid the masking effect of both natural and anthropogenic noise. However, the effect of surf-noise on the song structure of passerine birds has never been studied. Here, we present the first analysis of this kind based on Rufous-collared Sparrows (Zonotrichia capensis) living along the coastal environment in central Argentina. This species? song includes an introduction composed typically by 2 to 5 whistled notes, and a final trill, composed by a variable number of rapidly descending notes repeated at a regular rate. In January 2020 we recorded the songs of 30 individuals living close to the coast (less than 200 m from the surf zone) or far inland (between 500 and 1000 m from the coast) where the surf-noise is negligible. We also measured noise levels after recording each individual using dBX software. The spectrographic analysis using the Raven software showed that the trills of coastal individuals have higher minimum frequencies and narrower bandwidths compared to those of the inland. We interpret these results as evidence that Rufous-collared Sparrows living near the surf zone modify their song to avoid the masking effect produced by the low frequency noise generated by sea waves.