Wing kinematics differ depending upon a bird's wing design and flight speed. (A) Birds with pointed, high-aspect ratio wings such as the pigeon Columba livia transition from tip-reversal upstrokes during slow flight to feathered upstrokes at intermediate speeds and a swept-wing upstroke during fast flight. (B) Birds with rounded, low-aspect ratio wings such as the black-billed magpie Pica hudsonica use a flexed upstroke at all flight speeds. Shown are wingtip (filled circles) and wrist (open circles) paths in dorsal and lateral view
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