As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.

Friday, 29 July 2016

Hummingbird vision wired to avoid high-speed collisions


Date: July 18, 2016
Source: University of British Columbia

Hummingbirds are among nature's most agile fliers. They can travel faster than 50 kilometres per hour and stop on a dime to navigate through dense vegetation.

Now researchers have discovered that the tiny birds process visual information differently from other animals, perhaps to handle the demands of their extreme aerial acrobatics.

"Birds fly faster than insects and it's more dangerous if they collide with things," said Roslyn Dakin, a postdoctoral fellow in the UBC's department of zoology who led the study. "We wanted to know how they avoid collisions and we found that hummingbirds use their environment differently than insects to steer a precise course."

Scientists at UBC placed hummingbirds in a specially-designed tunnel and projected patterns on the walls to figure out how the birds steer a course to avoid collisions when they are in flight. They set up eight cameras to track the movement of hummingbirds as they flew through a 5.5-metre long tunnel.

"We took advantage of hummingbirds' attraction to sugar water to set up a perch on one side of the tunnel and a feeder on the other, and they flew back and forth all day," said Douglas Altshuler, associate professor in the department of zoology. "This allowed us to test many different visual stimuli."

While not a lot is known about how birds use vision in flight, it is known that bees process distance by how quickly an object goes past their field of vision, like we do as we drive down a road. As we pass by telephone poles on the side of the road quickly, our brains understand that the objects are nearby; buildings in the distance will take some time to pass, letting us know they are further away.

When scientists simulated this type of information on the tunnel walls, the hummingbirds didn't react. Instead Dakin and her colleagues found that the birds relied on the size of objects to determine distance. As something gets bigger, this may signal to the birds that they are getting closer, and as something gets smaller, it may signal that they are moving farther away.



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