Video of four and six bar wing mechanisms from How pigeons couple three-dimensional elbow and wrist motion to morph their wings

Including wrist bones in a six-bar mechanism improves the model's performance in tracking measured wing bone motion. This video compares the four-bar wing model with fused wrist bones and a full six-bar wing model with the measured bone locations (both mechanisms are shown as cartoons in Figure 6). The measured locations of the large bones are shown in grey, while the modeled bones are shown in color.