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Of Birds and Brains: a lesson in humility

Bill Meredith

I used to see hummingbirds around the house when midsummer flowers were In bloom, but we never fed them until last summer; we started then only because one of my grandchildren got me a feeder for Christmas. Sometime in June I remembered it, and hung it outside the kitchen window. It was a month or more before the hummingbirds found it; thereafter, they were regular daily visitors. 

There were at least two pairs of them, and one of the males established his territory around the feeder. He grudgingly allowed his wife to feed, but aggressively attacked all others; sometimes he would perch on the hanger above the feeder and flash the iridescent red feathers on his throat for all to see, and at other times he would hide in the nearby plum tree and ambush the interlopers. This went on until the first of October, when he left for his migration to Central America.

Early on the 10th of May my wife woke me up and told me the hummingbird was back, and when I sat down to breakfast he came and buzzed around the window several times. Since I hadnít yet put the feeder out and there were no flowers in the area, I assumed he was the same one who was here last year. The logical conclusion is that he remembered the feeder was there, and was looking for it. When I reflected on that, and on everything else I know that bird has done, I found myself thoroughly amazed.

According to one of my biology books, the average adult humanís brain weighs about three pounds and contains over 10 billion nerve cells. An entire hummingbird weighs about a tenth of an ounce, most of which is accounted for by the muscles that work the wings; I donít know how big its brain is, but it canít be more than 1/10 of the bodyís weight. A little basic arithmetic gives me an estimate of about 2.5 million nerve cells in a hummingbirdís brain. I recall reading somewhere that it takes over 100 nerve cells for a rat to learn to make a left turn in a maze. If that is so, 2.5 million cells in a hummingbirdís brain hardly seems like enough to account for all it can do.

Of course, the birdís brain is arranged differently from ours. The cerebellum, which controls muscle coordination, has to be relatively larger in birds. I havenít found a text to prove it, but It seems to me that a bird would need at least half of the cells in its brain just to coordinate routine flight activities. When my hummingbird is hovering still in the air and poking its beak up into a columbine blossom, its wings are beating about 100 times a second; and this is not just a simple back-and-forth motion. 

To hover, the wings have to follow a sort of figure-eight motion, which gets even more complicated when flying backwards or changing direction. Over a dozen pairs of muscles in the breast, back and wings have to contract and relax in an orderly sequence 100 times each second! Then, from a hovering start, he can accelerate to over 50 miles per hour and fly through a tree without hitting any branches or leaves. Youíd think this would require a cerebellum so big as to make him front-heavy and drive his beak right into the ground... but, amazingly, that doesnít happen.

Most of what birds do is the result of inherited behavior patterns called instincts; they can augment these abilities to some extent by learning, but their basic repertoire is limited to what their species has evolved in order to survive. Hummingbirdsí brains are "pre-wired" to recognize the colors and shapes of flowers they can feed from; they may remember where flowers are and come back to them, but the parents donít have to teach the babies what a flower is. 

The female knows automatically how to collect lichens and spider web silk to make her nest; she gets no lessons in homemaking from her mother. Last summer I watched the male and female perform their mating dance by flying at high speed in a vertical circle some 20 feet in diameter, buzzing their wings like revved-up racing motors and clicking their bills; what they did was exactly like the diagram in my bird book, but they had never read it.

 When they left Emmitsburg last fall the young ones did not stay with their parents, yet they flew to Louisiana, stoked up on nectar to build body fat, and then flew non-stop across the Gulf of Mexico without a map or compass to spend the winter in Panama with the others of their kind from all over North America. And then when the lengthening days stimulated their pineal glands this spring, they made the reverse journey north without consciously thinking about it and ended up in my yard, buzzing about indignantly because I, with my 3-pound brain, hadnít remembered to put the feeder out on time.

When I taught biology, I found my students tended to look down on animals whose brains are limited to instinctive behavior. It was part of my job to teach them that in biology survival is what counts, and in terms of survival a hummingbird is just as successful as we are. And the real joy of teaching came when they realized that even though our "superior" brains allow us to understand a hummingbird, we can still be amazed by it.

Read other articles by Bill Meredith