It's closer than you might guess, but hummingbirds continue to outpace human engineers when it comes to aerodynamic know-how.

A recent study by researchers from Stanford University, Wageningen University, Eindhoven University of Technology, and the University of British Columbia, pitted a surveillance drone against the flight efficiency of a hummingbird. While we might be excused for thinking, "Not even close; hummingbirds for the win!" the results weren't quite so lopsided.

The researchers found that while the best of the hummingbirds tested was more than 20 percent more efficient than the drone, the typical hummingbird was about as efficient as the man-made bird.

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The team studied the wings from hummingbird specimens stored in museums, looking for insight into how the blades of a tiny drone could fare against a hummingbird's wings. At issue was efficiency vs. drag -- which apparatus was best, needing the least power, to triumph over the force (drag) that slows the upward lift of either flapping wings or shiny helicopter blades.

The bird wings were measured and calculated for how much they would need to be flapped in order to attain lift. The results were compared with the specs of the "Black Hornet," a tiny British surveillance drone weighing just 16 grams.

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While the Anna's hummingbird species topped all comers -- bird or drone -- at this efficiency metric, most other hummingbirds were around the same level of efficiency as the Black Hornet.

"This shows that if we design the wings well, we can build drones that hover as efficiently, if not more efficiently, as hummingbirds," Standford University Professor David Lentink told BBC News, while noting that the little flappers made by Mother Nature were still way ahead of machines at visual flight control in crowded spaces and other skills.

"But if we focus on aerodynamic efficiency, we are closer than we perhaps ever imagined possible," Lentink added.

The team's work has been published in the Royal Society journal Interface.