Sunday, December 25, 2016

Bird Navigation Systems

That bird behind us would fly no more, but I would spend years trying to help future birds not end in a heap on the road.

Around the age of ten I was riding with my father through the countryside of western Ohio, gently rolling crop land on each side.  In this great volume of free space a single bird thumped our windshield.  Through the rear window I watched its final flight powered by inertia from the collision and guided by gravity to the ground.  The wind made its wing flutter farewell.

In dismay I turned to my father.  I probably asked why he had hit it, because questioning the motives of a bird would not even cross my mind.  He understood the spirit of my inquiry, placing the blame on neither him nor the departed creature, and said simply that the bird had lost its bearings.

I was confused by this answer but it had a certain ring of truth that my young mind began to process. While it seemed clear that animals would not choose such an end, if their mechanism for navigation were broken then accidents like this would happen often.  Maybe there was some way to fix this failing.

First, I had to find the bearings.  More specifically, I had to find the balls that must have escaped from the mechanical bearing rings behind the bird's eyes. Through my father or uncle or neighbor I knew that bearings often failed due to damage or loss of these little spheres. When my father said the bird had lost its bearings, it seemed obvious that he meant the balls had fallen out of the bird's head.  I wondered if they would be shiny like metal, but there was no question that they would be tiny.  I figured there would be two rings, one for each eye, and several spheres within each.  Given the size of a bird's head this meant that the ball bearings would be very small and hard to find.

I searched the ground for bird bearings and considered how to use them to reorient the birds.  I never came up with a solution short of surgery, because pushing the tiny balls back in past their eyes would probably not re-seat them properly in the rings for navigation. Of course, other problems loomed even earlier such as how to identify a bird that needed new bearings. And there was the fact that I did not find a single bearing in the woods or anywhere outside.  Seeing flocks over fields gave me the sense that such concentrations might mean a greater chance that bird bearings might be found there. Even more might be in these fields, having accumulated from years of migration over grain-rich land. Waiting for spring I walked on neighboring farms after the plows had brought aged soil to the surface.

Pride in my hypothesis turned to disappointment, for never did the glint of a bird bearing against a dark loam background catch my eye.  Almost too many years later to admit I discovered the much simpler hypothesis that birds do not have physical bearings that fall from their head causing them to slam into moving silica.  The longer lesson was that my understanding of the world and words could be wrong but correctable.  And the best lesson was that thinking about nature while walking in fields and woods is a good way to spend part of life, even if I do not find what I am looking for.

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