Aggression by Australian magpies Gymnorhina tibicen toward human intruders

The pattern of aggressive behaviour by Australian Magpies Gymnorhina tibice n toward human and heterospecific intruders was studied at rural and suburb an sites in the Brisbane area during the 1994-95 breeding season. Both non- intrusive observations and experimetal intrusions were used. All observatio ns were based on breeding pairs. Preliminary observations of suburban pairs indicated that some were consistently aggressive toward humans ('aggressiv e') while others were not ('non-aggressive'). In virtually all cases (97.5% ), only males were involved in attacking humans; however, females were equa l or more prone to attacking non-human intruders as males. None of the rura l Australian Magpies reacted to human intruders, although they attacked het erospecific intruders as frequently as did aggressive birds. The patterns o f attacks during the breeding season showed a peak in the late nestling pha se, immediately before the fledglings left the nest.