The hummingbird's special hovering ability is crucial to its survival, with the bird relying on this to feed on flower nectar. A pair of researchers, however, has found that if this hovering ability were a program, it would have some glitches in the system or, at least, some limitations.

University of British Columbia researchers Benjamin Goller and Douglas Altshuler have found evidence that hummingbirds encounter problems controlling their hovering flight when there is background motion in their field of view.

For their study published in the journal PNAS on Dec. 8, the researchers came up with a virtual reality environment characterized by visual patterns displayed to freely flying hummingbirds in order to determine the role of vision in the tiny flappers' ability to control their hovering flight.

In laboratory experiments, Goller and Altshuler projected images behind a bird feeder to see how these influence the hummingbirds attempting to eat at the feeder. They observed that images of moving gratings and rotating spirals result in the birds flying more haltingly, repeatedly drifting away from the feeder and drawing their beaks away.

Interestingly, the birds did not get used to the moving images even as the researchers conducted the same experiment again. The little creatures were still unable to adjust and adapt to these distracting images.

The researchers also observed that once the beak of the bird broke contact with the feeder, the hummingbird's brain appears to do a sort of reset. The bird comes back to its starting hovering and feeding position only for it to be distracted by the moving images again. The researchers said that this suggests a stabilization reflex that is triggered by the hummingbird's visual processes, which kick in when the bird attempts to hover.

"Despite the urge to feed, the birds seemed unable to adapt to the moving images," Goller said. "It suggests the hummingbirds' visual motion detection network can over-ride even a critical behavior like feeding."

While moving images have unwanted impact on the birds, the creatures appeared to have no response when the researchers projected still images, and this indicates that the birds control their hovering position by stabilizing movement in their visual field.

Goller and Altshuler said they found this process to be surprisingly sensitive for a bird with special abilities in visual processes and spatial mapping.

"The high sensitivity and persistence of this disruptive response is surprising, given that the hummingbird brain is highly specialized for sensory processing and spatial mapping, providing other potential mechanisms for controlling position," the researchers wrote.

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