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Beak 'Handedness,' Crows Favor Left or Right Too

Dec 30, 2014 11:25 AM EST

It turns out that crows favor the left or right side of their beak just like humans favor their left or right hand when holding tools. This draws even more intriguing parallels between the clever black birds and humans. However, according to a new study, this may have a lot more to do with bird eyes than "handedness."

The study, recently published in the journal Current Biology, suggests that a crow's bill-side preference is designed to keep the tip of its tool in sight of its best eye - a strategy to ensure some impressive beak-eye coordination.

Like most animals, humans too have a dominant eye (you can determine your own eye dominance with a simple test) - that is, an eye that best measures and ultimately determines the relative position of an object. Interestingly, this is but a factor that influences handedness, and those who are left handed are not necessarily also left-eye dominant. Recent research has indicated that handedness may also have a lot to do with which hemisphere of the brain develops more rapidly, leading to an early preference for one arm or the other.

This may hold true for birds too, in which a crow may favor one leg over the other for grasping things. However, in the case of tool use, it's all about the eye. That's because crows have what is called "extreme binocular vision" - characterized by an unusually wide field of view in comparison to other species. However, this wide field of view comes at a price.

"We thought that their binocular fields would facilitate binocular vision, perhaps allowing the birds to judge the distance from tool tip to target," zoologist Antone Martinho of Oxford University explained in a statement. "It turned out that, most frequently, they only see the tool tip and target with one eye at a time."

And if you can only use one eye when guiding a tool, you would want to use your best one, thus the beak-side preference.

Of course, crows are not alone in understanding the importance of eye dominance. Human sportsmen frequently emphasize the importance of learning this dominance even before learning to play pool or fire an arrow.

"Birds and humans face similar problems in tool use and many other activities," study author Alex Kacelnik added. "Studying similar problems across species helps to put all of them in perspective."

And, as the crow teaches us, it really all comes down to getting the best perspective.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

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