VANDERLEEUW, A.H.J.*; BOUT, R.G.; ZWEERS, G.A.: Control of the cranio-cervical system during feeding in birds.

The avian neck is a complex, kinematically redundant system, that plays a role during i.a. food prehension and manipulation. The kinematic redundancy is resolved by movement principles, e.g., Fowl move their necks according to a geometric principle that maximizes rotation efficiency. The movement pattern shows large rotations in some joints, while keeping the other vertebrae more or less as straight bars. Waterfowl show a pattern of successive, rather than simultaneous rotations, in the rostral part of the neck. A kinematic model shows that the geometric principle only produces a Waterfowl-like pattern if a constraint on the movement of the caudal vertebrae is introduced. The constraint is related to the amount of stretch in the long dorsal neck muscles, which have a different configuration in Waterfowl. To investigate whether the difference in movement pattern result from differences in either anatomy or neuromotor patterns, the EMG of neck muscles was compared between Mallard and Chicken for drinking, pecking and inertial feeding. The results show large differences: 1. In mallards, considerable overlap is found in the activity of antagonist, but not in chickens. 2. Dorsal muscles in the rostral part of the neck are activated successively in mallards, rather than simultaneously as in chickens. 3. In mallards, ventral and dorsal muscles are active during the backward and forward movement of inertial feeding respectively, but the reverse is found in chickens. We conclude that the difference in movement patterning between Chicken and Mallard results from a difference in the control system of the neck, which may have evolved as an adaptation to aquatic feeding in Waterfowl, but is also evident in various movements above the water surface and on land.