Meeting Abstract
Birds can morph their wings through a remarkable range of motion, enabling them to surpass insects, bats and aircraft in their ability to fly in varied environments. While bird wings bones are homologous to human forearm bones, the bird wing has a unique coupling between wrist and elbow motion allowing them to automate wing flexion and extension. Planar drawing parallel mechanisms have been used to model this motion in the past, but have not been corroborated with quantitative data. Here we measure how the skeleton of a pigeon (Columba livia) moves during wing morphing. With this data, we show that wing skeletal motion is actually highly nonplanar, highlighting the limitations of the drawing parallel mechanism. To elucidate the internal mechanism, we evaluate a series of hypothetical mechanism layouts including four-bars similar to the drawing parallels and those which include the wrist bones. We find mechanisms without any wrist bones to be anatomically infeasible, because they require the radius and ulna to cross to accurately match measured skeletal kinematics. Incorporating the wrist bones, we find better fits to our data as well as anatomically realistic mechanisms and recover a roughly parallel radius and ulna arrangement. This helps to demonstrate the importance of the wrist bones and coupling to avian flight.
