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Hummingbirds Avoid High-Speed Collisions Thanks To Their Eyes

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Researchers have found that hummingbirds process visual information differently from other animals, allowing them to avoid high-speed collisions while in midair.

Hummingbirds are agile fliers, traveling faster than 31 mph, but capable of stopping immediately to navigate through vegetation. Given the speed they fly in, hummingbirds are in danger if they collide with anything in their surroundings.

"We wanted to know how they avoid collisions and we found that hummingbirds use their environment differently than insects to steer a precise course," said Roslyn Dakin, a postdoctoral fellow from the University of British Columbia's Zoology Department and the lead of the study.

The researchers created a special tunnel and placed the hummingbird subjects inside, projecting patterns on the tunnel walls to observe how the birds will come up with a way to prevent collisions while they are flying. There were eight cameras set up to record the hummingbirds' movements as they flew within a tunnel, about 18 feet in length.

Hummingbirds like sugar water, thus, the researchers used that to lure the birds and make them fly back and forth the feeders located at either end of the tunnel.

There's not a lot of information about the role of vision in bird flight. Bees, however, process distance depending on how quickly they pass an object. This means that as they pass a certain flower, for instance, they understand that flower is nearby. It's actually a lot similar to how people perceive distance.

When the researchers tried to simulate a similar situation in the tunnel, they saw it didn't register a reaction from the hummingbirds. Dakin and colleagues then realized that the birds focused instead on object size and not proximity to gauge distance. As such, the bigger an object is, the nearer it is, and vice versa.

As objects in their field of vision grow bigger, the hummingbirds are able to gauge how much time they have until a collision with the objects was imminent.

Additionally, the researchers discovered that the hummingbirds utilized a technique called image velocity. Flies have also been observed to use the technique, which helps them assess how high up in the air they are. When the researchers adjusted the tunnel wall patterns, making them appear to move up and down, they observed that the hummingbirds adjusted how they were flying accordingly.

Douglas Altshuler and Tyee Fellows also contributed to the study, which was published in the journal Proceedings of the National Academy of Sciences.

Photo: Andrew E. Russell | Flickr

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