Researchers at Lund University have identified previously unknown characteristics of European nightjar flight through wind tunnel experiments, revealing how the birds balance competing aerodynamic demands. The nightjar undertakes extensive annual migrations between Europe and southern Africa while also requiring the ability to hunt insects through slow, maneuverable flight.
Wind tunnel studies measuring airflow patterns showed that the nightjar’s broad wing tips, beneficial for slow-speed maneuverability during insect hunting, create disadvantages at higher speeds by reducing lift generation efficiency. This finding contradicts assumptions that long-distance migrants necessarily possess wings optimized primarily for efficient sustained flight. According to Christoffer Johansson, an associate professor at Lund University, the nightjar’s wing design represents a compromise accommodating multiple functional requirements rather than specialization for a single purpose.
The research also documented an unexpected aerodynamic mechanism in which nightjars generate thrust during the upward wing movement, or upstroke, of their wingbeat cycle. This active upstroke thrust generation had previously been documented mainly in bats and insects rather than birds, suggesting convergent evolution may have produced similar aerodynamic solutions across distantly related flying animals.
Johansson noted that the upstroke capability becomes relevant when wing folding is mechanically restricted, enabling alternative thrust generation methods. The findings underscore how evolutionary pressures can favor designs balancing several functions over single-purpose optimization.
The research team plans to investigate whether this flight mechanism appears across other bird and flying animal species or represents a specialized adaptation specific to nightjars. Understanding these principles could also inform development of flapping-wing aircraft and drones facing similar mechanical constraints.
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