Example kinematic traces for takeoff, mid-flight and landing for bird 2. Arrows indicate the direction of wingtip movement during downstroke. Top panels show wingtip position relative to the shoulder for each wingbeat. Gray crosses indicate the location of the shoulder when the origin is not shown. Lower panels show wingtip position in the global coordinate system, with tick marks indicating distance from the perch. The traces illustrate the changes in stroke planes from negative angles during takeoff and mid-flight to positive angles during landing. The steeply tilted stroke planes during takeoff account for the compressed appearance of the wingtip path in the dorsal view during takeoff. These trends in stroke plane angle (SPA) are evident for both local and global coordinate systems.