Hummingbirds, whose supreme hovering ability is the key to their survival by allowing them to feed in mid-air on the nectar in flowers, may have a "glitch" in that ability the tiny birds cannot control, researchers say.
Experiments at the University of British Columbia proved the tiny flappers lose a bit of their in-flight hovering expertise if there is background motion within their almost 360-degree field of view.
Projecting moving images onto a wall behind a hummingbird feeder in their laboratory, researchers Benjamin Goller and Douglas Altshuler found that images such as a rotating spiral or shifting stripes caused the birds to fly more erratically.
As the birds tried to achieve contact between their beaks and the flower, the motion behind the feeder would cause them to drift away, the researchers say.
"Despite the urge to feed, the birds seemed unable to adapt to the moving images," zoologist Goller says.
Once the hummingbird's beak lost contact with the plastic feeder, its brain appeared to experience a kind of re-boot, the researchers say, and the bird would reestablish its intended hovering position only to have it disrupted again by the movement in its field of view.
Projected still images didn't seem to affect the birds, suggesting movement may interfere with birds' technique of hovering that requires them to stabilize movement in their visual field.
That stabilization reflex may be a vital part of their spatial mapping and visual processing crucial to their hovering expertise, the researchers said in reporting their study in the Proceeding of the National Academy of Sciences.
"It suggests the hummingbirds' visual motion detection network can override even a critical behavior like feeding," Goller says.
The study is the first to directly measure impacts of moving visual patterns on the free flight of birds.
"We were very surprised to see how strong and lasting the disruption was -- birds with hovering and feeding abilities fine-tuned to the millimeter were off the mark by a centimeter," says Goller. "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."
https://news.ubc.ca/2014/12/09/ubc-team-finds-a-glitch-in-hummingbird-hovering/
