This bird cheats at flying — it makes thrust on the upstroke, like a bat

Researchers at Lund University flew European nightjars — nocturnal migrants that travel between Europe and southern Africa — in a wind tunnel and measured the air behind their wings. They found the bird's broad wingtips, ideal for slow hunting flight, cost it lift efficiency at cruising speed: a compromise, not a perfectly optimized wing. The surprise was the upstroke: the nightjar generates real thrust as its wings rise, a trick previously thought to belong mainly to bats and insects. The team thinks restricted wing folding is the key, and that the phenomenon may be widespread among birds — with lessons for flapping drones and flying robots.