SONG IN CHIPPING SPARROWS, SPIZELLA-PASSERINA - STRUCTURE AND FUNCTION

Bird song is thought to function in territory defence and mate attraction. This 'dual function hypothesis for song in male chipping sparrows was tested using two approaches. Males of this species each sing a single, simple, individually distinct song type. It has been hypothesized that selection should favour this type of song structure when song functions primarily in territorial defence. First, male responses to playbacks of songs of territorial neighbours and strangers at the boundary of a subject's territory were compared. If song functions primarily in territory defence, theory and previous studies suggest that males should respond more strongly to strangers than to neighbours. Although males did respond, there was no difference in the response to neighbour and stranger playbacks either before or after the onset of incubation. Second, the pattern of song output was examined during different stages of the breeding cycle. Song output declined to near zero after pairing, but resurged dramatically when males lost mates. These results suggest that chipping sparrow song functions primarily in mate attraction, contrary to predictions based on song structure. (C) 1995 The Association for the Study of Animal Behaviour