Date of this Version
Distress call playbacks are used as deterrents to keep birds out of areas where they are causing problems. However, the calls often are ineffective, owing to birds' rapid habitation to them. Recent studies on the functional significance of distress calls indicate that adult passerines only distress call when physically constrained and that the calls are designed to startle the predator holding the caller into releasing it. Further, distress calls attract other birds, which approach the caller to acquire information about the predator. These findings suggest that distress calls would be more effective if their broadcast is paired with a predator model that appears to be grasping the caller. Such a pairing should reinforce a bird's fear of the predator model and delay its habituation to the distress call.