Selective feeding in birds depends on combined processing in the left and right brain hemisphere.

During visually guided foraging birds tend to select certain types of food from a mixed diet. This selectivity is ecologically relevant. During scanning for food birds spot the surroundings mainly with the monocular lateral visual field of the one or other eye and then control pecking with their small binocular frontal visual field. As the visual systems of the avian left and right brain hemisphere are supposed to work largely independently in the short term, the problem arises of how the avian brain handles a task that requires coordinated activity of the left and right brain hemisphere for efficient processing. Here we report that chicks exhibit strong selective feeding when both of the brain hemispheres are involved. With the left or right hemisphere alone selectivity is reduced or completely absent. Our findings reveal a marked qualitative difference between unilateral and bilateral processing. They highlight an important but so far unexplored selection pressure for the evolution of hemispheric cooperation.