On a Nebraska Cornfield, Birdwatchers Respond To the Call of the Cranes

Witness the spectacular migration of the most ancient of bird species

By , Staff writer of The Christian Science Monitor

Bundled against the chill of a March morning, we gathered in predawn darkness in a Nebraska cornfield, bathed in the silvery light of a full moon. Paul Tebbel, the lanky bearded director of the Audubon Society's Rowe Sanctuary, cautioned us to remain absolutely silent as he led small groups across the field to a two-story wooden blind built on the bank of the Platte River.

We had come to witness one of the most spectacular natural events in North America - the migration of a half-million sandhill cranes, funneling through the Platte River basin, as they have done every spring for millions of years. It is by far the largest concentration of cranes anywhere in the world - part of a vast movement of geese, ducks, and other waterfowl numbering up to 9 million birds passing through this region of flat lands and shallow marshes.

For birders like me, this was a long-awaited pilgrimage. Mr. Tebbel laughingly calls it "the Super Bowl of bird-watching." But even for the casual observer, the cranes of the Platte offer a spellbinding experience of nature that will never be forgotten.

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The elegant, long-legged gray cranes spend their nights crowded onto the sandbars of a 70-mile stretch of the river, whose shallow waters provide warning of the approach of coyotes. After spending their winters in the south central US and Mexico, the cranes spend about a month here. They forage by day in the fields for corn kernels, worms, and insects to fatten themselves up before heading to their nesting grounds on the Arctic tundra.

A chorus of avian voices

In the darkness, the cranes were still not visible, except as indistinct clumps. But we could hear their calls, a long, vibrating bugling sound that can be heard for miles. At first the calls came singly, the almost plaintive sounds of early risers seeking company. Then others answered, the calls rising steadily to a chorus of avian voices that one author has dubbed "crane music."

As light filled the sky, the dark outlines slowly began to resolve into a vista of tens of thousands of cranes, some standing only feet from our hiding place, slowly rustling and moving.

Suddenly the sandhill cranes began to "dance." In a complex and fascinating display, they lower their heads almost to the ground, while lifting and spreading their wings. Then the elongated birds lift their heads, while pulling their wings down. Sometimes they literally jump. Two birds may face each other, dancing simultaneously. The behavior is infectious, spreading through groups of cranes in an almost ecstatic explosion of activity.

Cranes are among the most ancient of all bird species - there is fossil evidence of cranes in the Platte River basin going back about 9 million years. Perhaps because of their size and behavior, cranes have long fascinated mankind. Cranes are long-lived - some have lived in captivity into their 80s - and they pair for life. References to cranes fill the literature and art of human civilization, and in many cultures they have a mythic status as symbols of long life, happiness, steadfastness, and love.

Despite their almost revered status, cranes are also perhaps the most threatened family of birds. Of the 15 species of cranes worldwide, seven are considered endangered, as are two subspecies of sandhill crane. There are several species of sandhill cranes, but the most numerous is the lesser sandhill crane which, despite its name, stands four-feet tall. After one year, the crown of the bird is bare and the skin bright red.

Whooping cranes number less than 200 in the wild, and were saved from extinction only by the heroic efforts of scientists led by the International Crane Foundation, a Wisconsin-based research institution that has successfully bred and reintroduced cranes around the world.

George Archibald, founder of the ICF and probably the world's leading expert on these birds, combines a passion for cranes with a scientist's knowledge of their habits. Leading our group trip, Dr. Archibald alerts us to one of his discoveries - the cranes' "unison call," a series of notes uttered in a coordinated sequence by paired birds.

Gradually the cranes lift off from the riverbed and head for their daytime feeding and resting areas. They spread out into crop land, alfalfa fields, and grasslands, but prefer the cornfields where there is waste corn left behind after harvest. The corn accounts for most of the cranes' diet and for the buildup of fat needed to survive the lean times in their Arctic breeding grounds.

Ironically the spread of huge, mechanized farms in Nebraska since the 1930s has contributed to the concentration of the crane migration here and the expansion of their numbers. Mechanical harvesters leave behind far more grain in the fields than the old-style hand-picked methods did.

But the presence of people has also posed a threat to cranes and waterfowl migration. Dams and irrigation projects have diverted water from the Platte and its tributaries, shrinking the riverbed that is vital for protecting the roosting cranes. The birds are now concentrated into two small stretches of the river, only partly protected by conservation measures.

At the same time, fewer than 400 of the original 4,000 marshes remain in the Rainwater Basin Area adjacent to the Platte River Valley, a major staging area for waterfowl. The crowding of the waterfowl into small areas, scientists say, has allowed for the spread of avian diseases, resulting in the death of hundreds of thousands of ducks and geese.

A last-minute sighting

The Platte River basin is crucial not only for the survival of the sandhill crane but also for small numbers of migrating whooping cranes. I spent part of a day following reports of sightings in hopes of seeing this beauty. Ready to concede failure, I finally caught a glimpse of the tall, striking white bird, flashing its black-tipped wings as it joins a group of sandhills in a cornfield.

At the end of the day, crane watchers position themselves, in blinds or from bridges over the Platte, to watch the return of the cranes from their day in the fields. Their honking calls fill the air as the flocks begin to form above, a leader at the point. Archibald points out the cranes' parachutist-style landings, circling downward and then, at the last moment, dropping almost vertically with their legs dangling, their tail spread, and their wings cupped.

At first, only a few birds stand sentinel back on the sand bars and in the shallow waters. But soon they descend in great clouds and the islands of cranes form again, black and stirring, their throaty cries slowly fading as the sun sets in orange and pink over the Nebraska prairie.

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