HEAD-BOBBING AND HEAD ORIENTATION DURING LANDING FLIGHTS OF PIGEONS

1. The head-bobbing rhythm previously reported in pigeons Columba livi a during approximately level landing flights also occurs in upwards la nding flights. This finding strengthens the evidence that head-bobbing in flight is linked specifically to approach to a landing target, and that the behaviour has a visual function. 2. In both level and upward s flights, head-bobbing arises from an oscillating flexion and extensi on of the neck. Rhythms in translation and rotation of the body do not make a detectable contribution to head-bobbing. 3. Head-bobbing occur s at the same frequency as the wingbeat cycle and in a fixed phase rel ationship to it. 4. The orientation of the head relative to the horizo ntal is correlated with the trajectory of upwards approach to a perch. In contrast to downwards landing flights, this relationship cannot ha ve the function of keeping the perch in focus during landing. It is pr oposed instead that it enables the head to be bobbed along the axis wh ich maximizes amplification of optic flow.