Fig. 5. Gliding perching sequence (Run 9 of
Table 1) taken using high-speed
digital video camera. Time of frame t is shown at upper left of each
panel, referenced to the point of maximum wing flexion t=0 ms (D).
Phase 1 (A): gliding approach. Alula begins to peel upwards; tail flicked up
and back. Phase 2 (B–D): pitch-up manoeuvre. Wrist sweeps forward. (E)
Lesser underwing coverts begin to deflect from wrist (red arrow); alula starts
to protract; wing begins to straighten; tail spreads and pushes downwards and
forwards. (F) Lesser underwing coverts deflecting in travelling wave from
wrist towards shoulder (red arrow). (G) Lesser underwing coverts fully
deflected (red arrow). Phase 3 (H): deep stall. Wings outstretched to give
parachute-like shape. An animation of the complete sequence at 500 frames
s–1 is provided in supplementary material Movie 5.