Fig. 4. Wingbeat kinematics during hovering across a natural elevational gradient in the Peruvian Andes. Data are species mean for 43 species of hummingbirds. (A) Wingbeat frequency decreased with increasing body mass. The largest hummingbird is the giant hummingbird Patagona gigas, which is substantially larger than all other trochilid taxa and is considered an outlier. However, the decrease in wingbeat frequency with body mass is found even if P. gigas is removed from the analysis (inset; all P<0.001; see text). (B) Stroke amplitude increased with increasing elevation, mirroring the results of experiment 1 (Fig. 1). See text for regression equations.