Hummingbirds Have Trouble Hovering with Background Motion

Even superb flyers such as hummingbirds have trouble sometimes, with a new study showing that their graceful hovering ability is hampered by something as simple as background motion.

A pair of researchers, Benjamin Goller and Douglas Altshuler, from the University of British Columbia, projected images of moving spiral and striped patterns on a surface behind a bird feeder in a lab. With this kind of background motion in their field of view, the hummingbirds became increasingly disoriented, drifting away from the feeder as they tried to slurp its sweet nectar.

"Despite the urge to feed, the birds seemed unable to adapt to the moving images," Goller explained to Discovery News.

Even after adjusting and adapting to the moving images, getting used to them over some time, once they actually made contact with the feeder it brought them back to square one. A sort of reset button was triggered, bringing the birds back to their starting hover position where they were confused by the background motion all over again.

Still images, however, did not seem to hamper these masters of flight.

The scientists believe that hummingbirds are able to hover with such precision by stabilizing movement in their visual field. Anything that disturbs this spatial mapping and visual processing, no matter how slight, can through these flitters off.

"We think the hummingbird's brain is so precisely wired to process movement in its field of vision that it gets overwhelmed by even small stimuli during hovering," Goller said in a news release.

Normally, hummingbirds flutter so well that they outdo even a tiny helicopter, with a hovering capacity that is 20 percent more efficient in comparison. And another recent study attributes these hummingbird acrobatics to unsteady airflow mechanisms that generate vortices that produce the lift they need to fly.

The team's findings were published in the journal Proceedings of the National Academy of Sciences.

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