The European nightjar migrates thousands of kilometers between Europe and southern Africa, but its wings are not built like a typical long-distance traveler's. Researchers at Lund University studied the birds in a wind tunnel and found that their broad wing tips, useful for catching insects during slow, sharp maneuvers, become a disadvantage at higher speeds by reducing the efficiency of lift generation.
More unexpectedly, the nightjar keeps generating thrust on the upstroke, the upward part of each wingbeat. That active use of the upstroke has been seen mainly in bats and insects, suggesting that distantly related flying animals may have converged on similar aerodynamic solutions when wing folding is limited.
The findings, published in PLOS Biology, point to evolution favoring compromise over perfection. Understanding how the nightjar balances migration and hunting could also inform the design of flapping-wing drones, which may face similar mechanical constraints on wing folding.