Anthropogenic noise changes the acoustic environment in which avian signals have evolved, possibly decreasing active space or the area over which signals may be detected and discriminated by receivers. Linking signal transmission patterns to signal function and species’ spatial ecology is important for understanding behavioural changes of receivers in noise. We tested whether varying levels of ambient noise affectstransmission of two structurally distinct sections of male house wren (Troglodytes aedon) song used for short- and long-distance communication. We placed our experiment in an ecological context by measuring signal degradation and attenuation in relation to species-typical spacing patterns to investigate whether song structure is maintained within (short-distance within-pair communication) and between territories (long-distance male-male and extra-pair communication) depending on noise levels. Songs experienced more masking and fell below thresholds for detection and discrimination at shorter distances under noisier conditions. Decay of signal-to-noise ratios and cross-correlation factors in noise were so pronounced that song components used for both short- and long-distance communication did not transmit beyond average territory boundaries. Noise masking could affect species ecology: if signals are not detected by intended receivers in noisier habitats, settlement, space use and social interactions may be fundamentally altered compared to those in quieter environments.
Anthropogenic noise, signal masking, signal design, acoustic communication, song transmission, house wren