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No. 2477:
Sand Hill Cranes

Today, Sand hill Cranes. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Sand Hill Cranes are curious creatures -- unlike other birds. The male and female are almost indistinguishable. Both are drab gray with one startling splash of color, a red cap atop their heads. We watched a half million Sand Hill Cranes who'd paused in central Nebraska in their migration from the south to Alaska and even Eastern Siberia. 

During March, they rest by the sand bars of the Platte River fulfilling a curious role in symbiosis with the vast fields of corn milo, and soy on either side. They clean up the stubble, eating bugs and stray kernels before the Spring planting.

Two Sand Hill Cranes

Squadron at eveningFor nearly a month, the cranes rise early and go to the fields to eat and rest until sunset. They return in the evening, shouting their strange purring "Karrrooo" cry -- back to the cold river in wave after wave of irregular V-shaped squadrons of ten or of a hundred. And there they stand quietly 'til the next dawn.

These once-prehistoric creatures might be the oldest waterfowl on Earth -- highly evolved and highly adaptive. Think how they stand all night in the perfect safety of icy water on the sand bars. They limit the flow of blood into their legs. And their leg veins and arteries are close together, forming a counter-flow heat exchanger. That way, the blood that does return is preheated. 

I wonder if the similarity of male and female plumage is connected to the fact they mate for life. The males don't sell themselves with fancy clothes. And, once mated, the couple continues its ritual dances through their thirty or more years of life, facing one another and leaping into the air for the sheer joy of it. Their legs are surprisingly strong. If they're attacked, they fight back with powerful kicks. But to avoid attack they daub themselves with rust-colored mud as camouflage in the stubble. 

In the stubble

We began a surreal week with the cranes by filing into a viewing blind along the Platte River at 6:00 AM. As dawn displaced the blue/black night sky, their gray forms emerged and their trilling cries went from meditative to ear-splitting.


Some danced; some flew short circuits as they roused the world and the sun. Gradually, a few squadrons flew up and away, calling the others to follow. Thousands of cranes soon blotted out the sky. (The crane density along the river is some 24,000 per mile.) 

At the end of a week, we stood on a bridge watching waves of returning birds one evening. But now, lit by the last of the sun, they were no longer a gray blur. Now they were countless individuals, each shining orange against the dark blue sky. 


Over there, one crane led a small detachment across a patch of deep water to their evening's roost. In a river bend we see a couple doing its goodnight dance. And I realize that Houston might look this way to aliens from Mars. Would our individuality, first masked by our numbers, likewise emerge from our millions? Of course it would. It would have to be the same story.

I'm John Lienhard at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

This episode recalls an Elderhostel week with the Sand Hill Cranes and other birds -- a program run twice each year by Dr. Doyle Howitt, University of Nebraska at Kearny. My thanks to Dr. Howitt and to Beth Hoekje of Portland, TX, for their counsel. All photos by J. Lienhard

For video of the cranes, individually and en masse, see: this trio, and this huge flock.

Taking wing 

Returning at night 

Leaving the stubble