You wouldn't know it, looking out your car windows as you drive down Interstate 57 near Arcola, Ill., that you're passing through one of the most important bird areas in Illinois.

In summer, all you see are green waves of corn and soybeans. In winter, flat fields of corn and soybean stubble.

But for a few weeks in April and May, if you find the right places in the countryside southeast of Arcola, you'll see something else: thousands and thousands of American golden plovers, stopping over to rest and feed on their 10,000-kilometer round-trip migration from their wintering grounds on the pampas of Argentina to the shores of the Arctic Ocean.

All told, ornithologists estimate, about one-tenth of all the golden plovers in existence depend on the crop fields of Douglas County as a stopping point in their northward migration.

Ben O'Neal, a researcher at the University of Illinois, is studying the golden plovers and their relationship to these few square miles of east-central Illinois farmland. Last year, he and his crew of students counted about 14,500 of the birds, and this spring, they continued what has come to be called "The Plover Project."

"During the day, plovers were found in wet soybean stubble, but at night, they seemed to switch to standing corn stubble. Through this work, three areas were identified as perennial hot spots, each supporting more than 3,000 golden plovers at one time. Among them was a 6-by-6-mile area south of Arcola," he says.

Golden plovers have been noted as stopping off each spring in this area for more than 100 years, but no one was really certain what makes this area of Douglas County so attractive to the birds. Topography and soil hydrology seem to be important factors.

Before the advent of drainage ditches and tiling, the soils of Douglas County were among the wettest in the state. Some fields still are, forming ephemeral wetlands each year from March to May.

These wet areas attract golden plovers, which feed on insects in the soil. The bounty enables them to replenish their energy reserves for the final leg of their journey to their summer breeding grounds.

Because the golden-plover population is declining, the birds' stopover in east-central Illinois is more important than ever, O'Neal says.

But ornithologists aren't looking to make any changes in the way farmers manage their fields or their relationship with the birds. The plovers seem to be coexisting well with intensive row-crop farming methods.

O'Neal says no-till farming methods seem to benefit the birds most because they leave organic matter on the surface. And no-till benefits farmers, as well, by reducing erosion and protecting the soil.

Instead, he just wants farmers to be aware of the importance of their land to the golden plovers.