Movie 1.

The high-speed movie clip shows an example of a mandarin duck swimming horizontally underwater followed by an example of a pochard swimming horizontally underwater. Such movies from two cameras were used to analyze the paddling kinematics. Next, the clip shows a female mandarin duck swimming horizontally underwater using wing propulsion. This duck was an exception that used its folded wings for wing propulsion consistently in the experiments. Consequently, it was excluded from the study that focused on the foot-propulsion. The end of the clip exemplifies the digitized points on the foot used to analyze the kinematics.