Visual fixation of a landing perch by chickens.

Chickens were video recorded while making jumps or flights toward a landing perch, to test hypotheses about visual fixation behaviour. In the first experiment, varying the height above the landing perch of the food container providing the incentive to jump had no effect on head orientation, indicating that the birds were not fixating this object. In the second experiment, hens jumped over six combinations of perch height and distance, and a linear relationship was found at take-off between head orientation and the angular distance of the perch from the horizontal at the eye. This relationship is consistent with fixation of the perch by a linear combination of head and eye rotations, with the head component contributing 73% of the total response. The image of the perch is fixated 20 masculine below that of the bill tip, outside any region of the chicken retina specialised for high acuity vision. Fixation of the perch before jumping must therefore have some function other than inspection with high acuity, such as providing a constraint that enables precise visual control of trajectory and landing manoeuvres.