Hemispheric specialization in Australian magpies (Gymnorhina tibicen) shown as eye preferences during response to a predator.

Brain lateralization in birds is frequently expressed as a preference to view stimuli with one eye using the lateral monocular visual field. As few studies have investigated lateralized behaviour in wild birds, we scored eye preferences of Australian magpies (Gymnorhina tibicen) performing anti-predator responses. When animals deal with potential predators by mobbing them, constant assessment is needed to consider whether to approach, mob or withdraw. When presented with a taxidermic specimen of a monitor lizard, the magpies assembled on the ground close to the lizard and circled, pecked, jumped over, viewed and approached, or withdrew from it. Using video footage, the monocular fixations prior to or during performance of these activities were scored and the following significant eye preferences were found. Prior to withdrawing, the magpies viewed the lizard with the left eye (LE) (85% of events). Prior to approaching, the right eye (RE) was used (72%). Hence, the left hemisphere is used to process visual inputs prior to approaching the predator and the right hemisphere prior to withdrawing from it. This result is consistent with hemispheric specialization shown in other species, including humans. The LE was used also prior to jumping (73%) and prior to circling (65%), as well as during circling (58%) and for high alert inspection of the predator (72%). Mobbing and perhaps circling are agonistic responses controlled by the LE/right hemisphere, as also seen in other species. Alert inspection involves detailed examination of the predator and likely high levels of fear, known to be right hemisphere function.