Shorebirds send out plaintive cries as Ed Martinez strolls beside an enormous marsh known as Cheyenne Bottoms. He spots a long-beaked bird with stilt-like legs -- a killdeer. Now in his 70s, Martinez recalls learning the bird's name when he was only three. "My dad said that was a bird that said its own name. Killdeer. I've remembered that all my life. See how the little feet go ptptptpt? The plovers do the same thing."

Every spring, thousands of sandpipers, avocets, dowitchers, killdeer and other shorebirds stop by this marsh in Central Kansas before flying off to mysterious places. As a boy, Martinez wondered where do they go? And what do they listen for, that tells them it's time to travel? Those questions stayed with him as an adult. "You sit there and work with those birds, you wonder, I guess what you wonder is what makes them tick, and what are they listening for," he explains. "It's one of those mysteries that a lot of people don't even think about. But it's still there."

To learn more, Martinez devoted many years to capturing migrating shorebirds and putting a tiny ID band on each bird's leg. Once banded, he let the bird resume its journey, hoping that someday, somewhere, another naturalist might find it and register the discovery with the North American Bird Banding Program, a national site for bird banding data.

Aristocratic Europeans of the 17th century placed identifying bands on their falcons' legs, but the modern science of bird banding began in 1902. Today, naturalists like Ed Martinez catch birds, put an ID band on their legs, then release them. When the birds are caught again, information from the band can tell scientists how far and how fast it has traveled.

When Martinez began his effort in the 1960s, no one knew how far shorebirds migrated. Thanks to bird banding, scientists now have the answer, and so does Ed Martinez: "They travel a l-o-n-g distance. From the Arctic clear down to South America." Some shorebirds travel more than 24,000 kilometers, among the longest bird migrations in the world.

Figuring out these flights is a two-step process. First, someone must capture a bird, to put on the band. Then, the bird has to be recaptured, killed or found dead later, in a new location. To increase the odds of finding the same bird, twice, naturalists have always had to capture huge numbers. Ed Martinez estimates he's banded some 85,000 shorebirds since the 1960s. Helen Hands, a wildlife biologist at Cheyenne Bottoms, says that may be a world record, adding admiringly, "He probably banded for about 30 years and did shorebird surveys for 20 years. I guess [he] developed an interest in the place and made a tremendous contribution."

The data collected by Martinez helped scientists realize the importance of Cheyenne Bottoms for shorebirds on their long migrations. Over the years, the data gathered by banders here and around the world has shed light on bird lifespans as well as travels. And it's helping scientists identify changing migration patterns that can warn of habitat damage.

But banding takes time, and it stresses the birds. So scientists have been developing ways to track these flying travelers, without having to catch them twice. Danny Bystrak, a scientist at the North American Bird Banding Program, says these efforts make tracking birds easier and more efficient.

Bystrak says that larger birds can be fitted with large tags, whose ID can be read through binoculars. Another option is feather isotope analysis. That involves capturing a bird during the molting season and collecting a few, older feathers. The chemicals in feathers vary, depending on where the bird has lived, and some of those chemical "feather prints" are unique enough to identify the location. As yet another approach, many researchers now inject tiny transponders beneath a bird's skin instead of attaching a band, so they can track it constantly by radio.

These newer methods eliminate the need to catch the bird a second time. But, Bystrak says, only the second time. "The catching part of it, I don't see ever being replaced. Because in order to track a bird, you're going to have to do something to it, and to do that, you have to catch it.

As a naturalist whose bird catching career has led to better understanding of them, Ed Martinez says that he's glad that he spent so many hours, catching shorebirds then letting them go. "I'd rather be with them than with most people," he admits with a laugh. "Those little things can fly, and they can fly a long ways. It's just an amazing creature."

Thanks to bird banders such as Ed Martinez, the Western Hemisphere Shorebird Reserve Network lists Cheyenne Bottoms as a wetland of world importance.