Female song sparrow, Melospiza melodia, response to simulated conspecific and heterospecific intrusion across three seasons

To investigate female responses to territorial intrusion I presented female song sparrows with either a simulated female song sparrow intrusion or a simulated spotted towhee, Pipilo maculatus, intrusion as a control during either the prebreeding, breeding or postmoult seasons. Aggressive and nonaggressive behaviours and vocalizations were compared between intrusion types and across seasons. Principle components analysis suggested that female responses fell into three categories: (1) responses directed towards the intruder, mostly aggressive; (2) responses directed towards the mate; and (3) lack of response to the intruder. In every season, females responded more aggressively to simulated female song sparrow intrusion than simulated towhee intrusion. Responses directed towards female song sparrow intruders dropped across the three seasons and were significantly higher in the prebreeding season than in the breeding or postmoult seasons. (C) 2000 The Association for the Study of Animal Behaviour.