Impacts of noise on the response to territorial intrusions in hermit thrush (Catharus guttatus)

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University of New Brunswick


The obstacle that anthropogenic noise presents to songbird acoustic communication is well understood from the signaler perspective, but less is known about signal receivers. Using playback studies to simulate intruders on territories along a gradient of ‘urbanness’, the impact of both urban noise and experimental noise on hermit thrush (Catharus guttatus) territorial defense behaviour was quantified. Detection of the simulated intruder did not change as a result of urbanness or experimental noise. Responses to the intruder were less aggressive when experimental noise was present, but more swoops were performed near busier roads. As such, the urban anger hypothesis appears to be related to road presence, not noise level. When vocally responding to the intruder, experimental noise, but not urbanness, was associated with increased song amplitude and lower signal to noise ratio. Urban noise is less detrimental to hermit thrush than previously thought, but experimental and urban noise have different impacts.