Fig. 3. Rear view of the thrush nightingale in the wind tunnel. Consecutive frames spaced at 0.008 s intervals showing a complete wingbeat at U=5 m s^–1 (A), 7 m s^–1 (B) and 10 m s^–1 (C), starting with the upstroke (a) to the transition between upstroke/downstroke (e,f) and through the downstroke (j) to the transition between downstroke/upstroke.