Grasping in the pigeon: mechanisms of motor control.

A quantitative analysis of grasping in the pigeon suggests important functional similarities between the visuomotor controls of the avian beak and the primate hand. Beak-opening (gape) during eating is directly proportional to target size and the adjustment is completed prior to contact. The control of gape size involves variations in both the velocity and duration of jaw opening and these parameters are mediated by different effector systems (jaw muscles, neck muscles). Nerve section experiments were used to identify jaw motoneurons which are components of the final common path for grasping. Grasping in the pigeon approximates the functional complexity of mammalian visuomotor behavior but is mediated by a relatively simple effector system.