| Summary: | Anthropogenic noise may interfere with avian acoustic communication, however some species alter the structure of vocalizations, to improve transmission in noise. Here, I conducted playback experiments to determine whether compressor stations, generator or grid-powered screw pump oil wells, and overall ambient noise levels affected responses of Savannah sparrows (Passerculus sandwichensis) to conspecific alarm calls at their nests. I also measured the structure of alarm calls, to determine whether Savannah sparrows altered vocalizations in noise. On control sites, Savannah sparrows responded to alarm calls by delaying provisioning visits. At compressor station sites, the loudest infrastructure treatment, they showed less of a delay. Close to compressor stations, Savannah sparrows lowered the frequency and increased the bandwidth of alarm calls. These findings suggest the compressor stations may interfere with anti-predator communication, but that Savannah sparrows can alter the structure of alarm calls at these sites, perhaps mitigating some effects of noise. === October 2016
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