Figure 4.
Absolute value of the bound circulation Γbound and circulation from leading-edge vorticity (ΓLEV; in parentheses) around the 4 cm x-section throughout the wingbeat cycle. Not all birds were sampled at every position. Mid-downstroke circulation was significantly (p ≪ 0.05) higher than mid-upstroke in all birds (rh20, d.f. = 5; rh23, d.f. = 4; rh26, d.f. = 3) for which both positions were measured. Birds sampled: ×, rh18; diamonds, rh22; triangles, rh23; vertical line through ×, rh25; solid circles, rh26; open circles, rh27.