Predators and other natural enemies have

A simulated intrusion was accompanied in one condition by playback of song sparrow alarm calls, indicating the presence of predators, and in the other by playback of the songs of yellow warblers, Dendroica petechia, as a control. The eavesdropping avoidance hypothesis predicts that the birds should increase their use of soft song under increased risk of predation, but what the authors actually found was the opposite: the proportion of soft songs the subjects sang was significantly lower in the predator condition than in the control condition.