Aggression by Australian Magpies Gymnorhina tibicen Toward Human Intruders

Abstract

The pattern of aggressive behaviour by Australian MagpiesGymnorhina tibicen toward human and hetero-specific intruders was studied at rural and suburban sites in the Brisbane area during the 1994–95 breeding season. Both non-intrusive observations and experimental intrusions were used. All observations were based on breeding pairs. Preliminary observations of suburban pairs indicated that some were consistently aggressive toward humans (‘aggressive’) while others were not (‘non-aggressive’). In virtually all cases (97.5%), only males were involved in attacking humans; however, females were equal or more prone to attacking non-human intruders as males. None of the rural Australian Magpies reacted to human intruders, although they attacked heterospecific intruders as frequently as did aggressive birds. The patterns of attacks during the breeding season showed a peak in the late nestling phase, immediately before the fledglings left the nest.