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.
For 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.
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 more on the cranes, see the
US Wildlife
and Rowe Sanctuary sites,
and an article by Clara Johnson.
For video of the cranes, individually and en masse, see:
this trio,
this pair,
and this huge flock.
