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Signs of Spring Update: February 28, 2000

Today's Report Includes:

Leaping for Love

Our calendar says it's still winter, but birds don't have a clue about calendars. Sandhill Cranes notice the sun's angle in the sky and lengthening days, and something deep in their bones tells them it's time to head north, spring or not. What's on their minds? Romance!

By the middle of March, the birds that arrived first will be nice and plump. As they fatten up, they become more interested in romance and less interested in food. Then they start their courtship dance. Each pair spreads its wings and jumps and leaps into the air in a beautiful display that helps cement their pair bond.

Cranes mate for life, and stay together as a pair even during the winter. Most birds, like robins, take a new mate each year. Some, like Red-winged Blackbirds, mate with as many birds as enter their territory. Besides cranes, other birds that mate for life include Canada Geese, swans, ravens, and eagles.

Challenge Question #4:
"What do these species that mate for life have in common? Give reasons that would explain why these species might mate for life when others don't."

(To respond to this question, please follow the instructions below.)

Thousands Landing by Leap Year Day
The first cranes of spring 2000 arrived on the Platte River in Nebraska at the beginning of February. Just a handful arrived to begin with, but by February 16 there were hundreds right in the Audubon sanctuary, according to Bill Taddicken. He said the next south winds will bring a big push of cranes. He expects the Audubon sanctuary to have about 17,000 cranes by Leap Year Day.

Wally Jobman, in Grand Island, Nebraska, looks at the whole river. He said that several thousand cranes had arrived along the Platte as of February 17. Wally expects the first Whooping Crane, a lone individual who wintered with Sandhill Cranes in west Texas, to arrive any day now, but noted that it's too early for the Whooping Cranes that wintered in Aransas National Wildlife Refuge to be leaving yet.

Air Traffic Control, Crane Style
Cranes feed all day, and spend nights on the river. This means at sunrise and sunset tens of thousands of cranes are taking off and landing all at the same time. They don't have air traffic controllers to protect them from collisions, but they do have calls and body language to let each other know they're about to take off and where they're going. Before taking off, they let the cranes in their vicinity know what they're up to by leaping and flapping their wings and then making a pre-flight neck-stretch display.

Fattening and Fueling in Nebraska

Most of the cranes that spent the winter in western Texas, and some that wintered in Oklahoma and eastern New Mexico, migrate through central Nebraska every year. Each pair spends about four weeks fattening up before making the final long journey to the north. Some of the cranes that migrate through central Nebraska fly up to far northwestern Alaska and cross the Bering Strait into Siberia! The fat they put on in Nebraska is the fuel that will power their flight over those long miles.

The Sandhill Cranes and whoopers arriving in Nebraska are hungry! They'll spend their first week or two eating. Long ago cranes dined on succulent tubers of aquatic plants as well as frogs, insects, and small rodents. Now they get their plant food from acres and acres of cornfields, eating the wasted corn from the previous fall. Farmers don't plant the new corn until after the cranes have left in spring, so cranes do little or no damage to the farm fields.

Birdwatching at 70 MPH
About 400,000 cranes--that's 80 to 90% of all the Sandhill Cranes in the mid-continent population--stop for a month or so along a 60-mile stretch of the Platte River every March. Interstate Highway 80 runs alongside the Platte River in Nebraska. People driving along the highway at sunset can see thousands of cranes right from their cars as they speed along! During the peak of migration in mid-March, birders can see as many as 70,000 cranes and about a million geese in a six-mile stretch of river along the Audubon Society's Lillian Annette Rowe Sanctuary near Kearney. Bill Taddicken of the sanctuary said "The whole springtime here in Nebraska is an amazing thing--just amazing!"

World's Best Crane Stop

The Platte River was once called the river that was a mile wide and a foot deep. Long ago, water from Colorado rainfalls and melted snow from the Rocky Mountains rushed along this wide river valley every spring, scouring out tree seedlings and other land plants before they could get a toehold on the sandbars. A very wide expanse of river and sandbars was kept open this way. Cranes seem to need wide vistas to feel safe from predators, and after a day of pigging out in fields and meadows, they retreat to the river every evening to sleep close together in shallow water and on the sandbars. The river is shallow enough for them to stand in, while deep enough to discourage most predators.

Now most of the natural wetland and prairie has been replaced by farmland, and dams and other water projects have stopped the annual natural flooding cycles. With less water, the river has become narrow in many stretches, and without the annual surge in snow-melt water, huge cottonwood trees have taken root along much of the shore and on sandbars. So large stretches of river are now too closed-in for cranes. People at the Lillian Annette Rowe Sanctuary keep their stretch of the river open by occasionally burning and cutting trees down. As a result, their 6-mile stretch remains one of the best places in the world for migrating cranes.

Deadline Today for Challenge Question #3
Hurry, send your guesses today!

Last time we asked "When do you predict ice-out will occur this year on Thoreau's Walden Pond?" Today's the last day to enter the ice-out contest! Have you sent us your prediction?

Steve Maanum's class in Park Rapids, Minnesota sent not only a prediction, but also a great math class idea:

"Our 5th grade class in Minnesota took guesses that ranged from late Feb. to mid April. It gave us a chance to do a problem with range, mode, median, and mean. Our class guess for ice out on Walden Pond is March 10th."

Send YOUR prediction TODAY. Then we'll ALL wait for nature's answer, with Michelle Dumas reporting.

(To Respond to this question, please follow the instructions below.)

How to Respond to Today's Challenge Questions:

Please answer ONLY ONE question in each e-mail message!

1. Address an E-mail message to:
2. IMPORTANT: In the Subject Line of your message write: Challenge Question #3 (or #4).
3. In the body of the message, give your answer to the question above.

The Next "Signs of Spring" Update Will be Posted on March 13, 2000.

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