Immediate signaling flexibility in the model system Zonotrichia leucophrys nuttalli

Background noise can interfere with acoustic communication and subsequently influence signaling behavior. Immediate signaling flexibility (ISF) is a context-dependent form of behavioral plasticity that allows animals to temporarily change their acoustic behavior in response to noise fluctuations and potentially improve the chances of successful communication in noisy environments. However, the adaptive value of ISF is ultimately contingent on the response of the intended receiver, and there are differential effects on receiver response depending on which signal component is modified. Here, we describe ISF in the model system Zonotrichia leucophrys nuttalli using results from a noise broadcast experiment conducted in urban and rural locations. Three types of noise broadcasts were incorporated into the experimental design to test whether plasticity of song behavior, if observed, was dependent on the spectral qualities of the experimental noise. We predicted that all birds would exhibit ISF, but vocal plasticity would be greater in noisier territories. Instead, we found that only urban males displayed ISF by decreasing song bandwidth in response to experimental noise. Song modification did not change with type of noise broadcast or territory background noise, nor did it involve the temporary adjustment of trill structure traits used by receivers to assess vocal performance.