Head bobbing and the movement of the centre of gravity in walking pigeons (Columba livia)

The head bobbing of a walking bird is considered as an optokinetic response, but the question of why head bobbing is synchronized with leg movement is not clear. It is possible that head bobbing also has biomechanical correlation with leg movement at least during walking. Movement of the centre of gravity (COG) along the sagittal axis was estimated in pigeons Columba livia from carcasses and motion analysis from video films of walking. Although it was ascertained that the head thrust observed in the double support phase helps to shift the COG over the supporting foot around the beginning of the single support phase, its effect was very small. The hold phase showed correlation with the COG positioning over the supporting foot in the single support phase. Stabilization of the eyes during the single support phase may be significant for the control of balance.