A study of distress calls of song, swamp, and white-throated sparrows (Aves: Fringillidae). II. Interspecific responses and properties used in recognition

Recorded distress calls of each species were played to territorial males of the other two, in successive stages of the breeding cycle. Responses were like those given to intraspecific calls and showed a similar peak of intensity in the late nestling and fledgling stage.Song and swamp sparrows (Melospiza spp.) responded strongly to each other's calls, which are alike in length, carrier frequency, and frequency range and overlap broadly in rate of frequency modulation. However, responses were generally weak between Melospiza spp. and the white-throated sparrow (Zonotrichia), whose calls differ in these properties.Song and swamp sparrows responded strongly to artificial sounds that simulated their natural distress calls, but white-throated sparrows responded weakly to sounds that resembled their natural calls in some but not all properties.Song sparrows were exposed to artificial sounds that were varied in length, carrier frequency, and frequency modulation rate. With respect to each property, they responded strongly if the value fell within the range found in natural calls, but weakly if it fell outside this range. Evidently, all three properties are used in call recognition.We conclude that interspecific responses among these sympatric species resulted from similarities in their distress calls. Possible advantages of this behavior are discussed.