The Optokinetic Basis of Head-bobbing in the Pigeon

1. Head-bobbing of pigeons during walking and landing was studied using high-speed motion photography. 2. The analysis of film records indicated that head-bobbing whilst walking consists of two phases: one where the head is 'locked' in space but moves backward relative to its forward moving body; and another where it is thrust rapidly forward to a new position. 3. The fact that head-bobbing is abolished when pigeons walk on a treadmill suggests it is primarily a visual response rather than an equilibratory response. 4. Data are presented which show that stabilization during the 'lock' phase allows a small degree of slippage which is the probable source of error signals for compensatory head movements. 5. The head-bobbing that appears to occur during landing is shown to be illusory.