Fig. 6. Velocity fields, revealed using DPIV, of the wake of a baby chukar Alectoris chukar, 6 d.p.h., which was obviously struggling during WAIR at 65°. Backgrounds illustrate the bird (A) and vorticity, (B). Transparent red loop in A is an assumed 3D shape of vortex ring as inferred from concentrations of about and . Only a starting vortex () is visible. Compared with the wake of the baby in Fig. 3A,B (day 7, post-hatching), the wake is less organized and negative circulation () is less (40.5%).