Fig. 4
From: Birds repurpose the role of drag and lift to take off and land
Relatively high drag forces provide an expensive way to enhance total aerodynamic force. a High aerodynamic power requirements (normalized by pectoralis muscle mass) result from large drag forces during downstrokes and initial upstrokes, as shown for the same representative flight from previous figures. b Downstroke-averaged power requirements (filled bars) are much larger than upstroke averages (open bars), especially during mid-flight. Light pink lines and shaded regions show mean ± s.d. for the full wingbeat. c High instantaneous drag coefficients CD (red) and lift coefficients CL (blue) during maximum net force generation suggest the presence of a leading-edge vortex. d The high lift coefficients contribute to relatively high instantaneous power factors (CL1.5/CD), (e) while high drag coefficients result in relatively low lift-to-drag ratios (CL/CD). All bar plots show mean ± s.d. for N = 5 birds, n = 4 flights per bird (overlaid dots show individual flights). Source data are provided as a Source Data file.
