Fig. 6. Nectarivorous bats generate more upstroke weight support than fruit bats during slow hovering flight by inverting their wing further.

(A) All 17 hummingbird species converged on generating similarly elevated weight support during the upstroke. (B) The amplitude of upstroke weight support averaged over a 10% wingbeat interval (74 to 84% of the wingbeat cycle) confirms this (see table S1 for species names sorted by mass). (C) In contrast, nectar bats produce noticeably more vertical force during the upstroke than the fruit bat. (D) The vertical force amplitude is significantly different (78 to 88% of the wingbeat cycle). (E) This difference is explained by the radial angle-of-attack distribution for the upstroke (based on Fig. 3F), which shows pronounced differences in the angle of attack (<0%, inverted wing) of the wing tip (75 to 100% span). (F) At the wing tip, hummingbirds use angles around −15° to generate lift efficiently. Nectar bats (G. soricina, green; A. geoffroyi, orange) flick their wing tips back at around −35°, generating significant lift and drag, whereas fruit bats (Artibeus watsoni, purple) operate at −52°, generating more drag. Shaded areas and error bars represent SD across individuals. *P < 0.05, **P < 0.01 (light gray comparison bar; nonsignificant; see the “Statistical analysis” section).