An Investigation of Song-Based Species Recognition in the Red-Winged Blackbird (Agelaius Phoeniceus)

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Abstract
To determine the aspect(s) of male red-winged blackbird (Agelaius phoeniceus) advertising song which function in the transmission of species identity, 74 territorial adult male redwings were exposed to 173 playback experiments of normal and experimentally altered red-wing song during the 1977, 1978 and 1979 breeding seasons. Unaltered red-wing song and altered song containing species-identifying information evoked aggressive behavior from territorial redwings when played through a loudspeaker placed in their territories. A list of red-wing aggressive behaviors was compiled and the males' responses to altered and unaltered song were scored on a "hybrid-index" scale according to the number of times they performed each of the aggressive behaviors during the playback experiment. The results of the study indicate that 1) the ordering of the three song "syllables" did not affect the intensity of the males' agonistic responses to playback song and therefore does not convey species information, 2) the initial two syllables of the red-wing song do not encode the species-identifying information, as these two syllables, alone or in conjunction, failed to elicit fully aggressive responses from the males, 3) the last syllable of the song, a "trill", when presented to the males alone or in conjunction with the other song syllables, evoked fully agonistic responses, suggesting that this trill syllable encodes the majority of species-specific information in the red-wing song, and 4) by playing back increasingly shorter (in duration) sections of the trill syllable to the territorial males, it was demonstrated that the trill must be somewhat longer in duration than 180 msec to function in species identification. To determine the aspect(s) of male red-winged blackbird (Agelaius phoeniceus) advertising song which function in the transmission of species identity, 74 territorial adult male redwings were exposed to 173 playback experiments of normal and experimentally altered red-wing song during the 1977, 1978 and 1979 breeding seasons. Unaltered red-wing song and altered song containing species-identifying information evoked aggressive behavior from territorial redwings when played through a loudspeaker placed in their territories. A list of red-wing aggressive behaviors was compiled and the males' responses to altered and unaltered song were scored on a "hybrid-index" scale according to the number of times they performed each of the aggressive behaviors during the playback experiment. The results of the study indicate that 1) the ordering of the three song "syllables" did not affect the intensity of the males' agonistic responses to playback song and therefore does not convey species information, 2) the initial two syllables of the red-wing song do not encode the species-identifying information, as these two syllables, alone or in conjunction, failed to elicit fully aggressive responses from the males, 3) the last syllable of the song, a "trill", when presented to the males alone or in conjunction with the other song syllables, evoked fully agonistic responses, suggesting that this trill syllable encodes the majority of species-specific information in the red-wing song, and 4) by playing back increasingly shorter (in duration) sections of the trill syllable to the territorial males, it was demonstrated that the trill must be somewhat longer in duration than 180 msec to function in species identification.