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Distress calls, recorded from birds captured in mist nets, were played to territorial pairs in successive stages of the breeding cycle. Responses included approach, movement about the speaker, alarm calls, and displays. Latent time to response, closeness of approach, and numbers of movements and calls were measured.Males of all three species responded strongly in the nest building and egg-laying stage and weakly in the incubation and early nestling stage, when behavior is generally cryptic. A major peak of response, characterized by close approach and distraction displays, occurred in the late nestling and fledgling stage, when young are capable of emitting distress calls. Responses declined as juveniles became independent.Responses of females were generally weaker and more variable but the major peak was still evident.When a red squirrel or blue jay was exposed during playback to white-throated sparrows in the late nestling and fledgling stage, diving attacks and distraction displays were directed toward the "predator."Distress calls, normally given by a bird seized by a predator, may startle the predator and elicit harassment and distraction behavior from other birds. A responding individual learns the characteristics and location of the predator and may facilitate the escape of its mate or young.
Stefanski et al. (Fri,) studied this question.