Gargle vocalizations of black-capped chickadees: Test of repertoire and video stimuli

The gargle call is uttered by male black-capped chickadees, Parus atricapillus, during agonistic encounters; in fights between two birds, the gargler nearly always wins. Individuals vary in the number of different types of gargles they have in their repertoires. An experiment was conducted on captive chickadees to determine whether they had a greater aversive response to a larger gargle repertoire. The measure of aversiveness was the time spent away from the stimulus. Video images of a gargling chickadee or of no bird were paired with different gargle repertoire sizes as the test stimuli. The treatment causing the most aversive response was a video of a stimulus bird paired with a repertoire of three gargle types broadcast from a loudspeaker. Only low response was found when a vocal stimulus of three gargle types was presented without the video of the stimulus bird, or when the video was presented with no gargling. The treatment in which the video of a chickadee was paired with a repertoire of a single gargle type was of intermediate aversiveness. Black-capped chickadees find the presence of a potential rival that is giving a multiple-gargle repertoire to be more threatening than one giving a single-gargle repertoire. (C) 1996 The Association for the Study of Animal Behaviour