January 20, 2017 | David F. Coppedge

Fast Flight Specializations in Birds and Bats

When you are moving rapidly, you need to see things differently.

Hummingbirds

“Hummingbirds see motion in an unexpected way,” says Science Daily based on a paper in Current Biology. Think about that tiny flyer darting this way and that at your feeder, then speeding off in a flash. How does the world look to the bird? A key area of the brain in hummingbirds processes visual information in a “unique and unexpected way,” scientists at the University of British Columbia found.

“In all four-limbed vertebrates studied to date, most of the neurons in this [motion-detecting] brain area are tuned to detect motion coming from behind, such as would occur for an impending collision or when being attacked from behind by a predator,” says Douglas Altshuler of the University of British Columbia. “We found that this brain area responds very differently in hummingbirds. Instead of most neurons being tuned to back-to-front motion, almost every neuron we found was tuned to a different direction. We also found that these neurons were most responsive to very fast motion.

One doesn’t often see bruised hummingbirds lying on the ground from collisions, so the adaptation works well. It’s obvious even to children that these little birds are very special.

Earlier studies showed that the LM [lentiformis mesencephalic] in hummingbirds is enlarged in comparison to that of other birds. Scientists also knew that hummingbirds monitor and correct for any minor drift in their position as they hover.

Altshuler’s assistant Adrea Gaede added, “This study provides compelling support for the hypothesis that the avian brain is specialized for flight and that hummingbirds are a powerful model for studying stabilization algorithms.

Bats

Ever heard of an “acoustical field of view”? We’re used to our visual field of view, but in addition to sight, bats rely on sound to see their surroundings. A paper in PLoS One explores “Coordinated Control of Acoustical Field of View and Flight in Three-Dimensional Space for Consecutive Capture by Echolocating Bats during Natural Foraging.” How can bats go bam-bam! and catch two insects in succession while darting about in the dark? The scientists found out how:

The results showed that when the bats successively captured multiple airborne insects in short time intervals (less than 1.5 s), they maintained not only the immediate prey but also the subsequent one simultaneously within the beam widths of the emitted pulses in both horizontal and vertical planes before capturing the immediate one. This suggests that echolocating bats maintain multiple prey within their acoustical field of view by a single sensing using a wide directional beam while approaching the immediate prey, instead of frequently shifting acoustic attention between multiple prey.

Annie Oakley could hardly do better. So now you know; “echolocating bats coordinate their control of the acoustical field of view and flight for consecutive captures in 3D space during natural foraging.”

Interested readers may wish to follow another batty story from Science Daily about what Israeli scientists are learning from bat brains.  “Scientists have now identified the neurons that point bats in the right direction, even when their destination is obscured.” What they are discovering about grid cells in bats may lead to treatments for Alzheimer’s, they say.

Teach children to marvel at design in nature. It’s a crime to take such things for granted.

 

Leave a Reply