Postures of the avian craniocervical column

The avian cervical column comprises a large number of vertebrae and has far more degrees of freedom than necessary to position and orient the head. The large number of joints makes the avian neck a very suitable model for the study of coordination and movement strategies in kinematically redundant chains. A static optimization model that finds a solution for the configuration of cervical vertebrae is proposed and tested in a series of neck postures of a chicken. As inputs, the model uses length of the vertebrae, orientation of the articulation facies, and the position and orientation of the head with respect to the body. The model demonstrates that an even distribution of rotation over the whole chain is sufficient to explain all the essential characteristics of neck postures. It is shown that the model not only predicts static postures but also minimizes the change in angle needed to go through a series of successive postures. J Morphol 231:287-295, 1997. © 1997 Wiley-Liss, Inc.