Nancy Leo, left, peers through her binoculars as Helen Hewins describes a nest she saw Sunday morning at Perry State Park. Hewins and Leo, president of the Kansas Ornithological Society, were two of many birders to participate in the annual Christmas Bird Count sponsored by the National Audubon Society.

Perry ? Armed with binoculars, an iPod and a checklist of bird species, Nancy Leo, Janeen Walton and Helen Hewins set out Sunday to hunt some of the more than 400 species of birds that call Kansas home during the winter. More precisely, they were taking part in the Audubon Society’s annual Christmas Bird Count, which began in 1900 to counter the traditional bird hunting that occurred on Christmas Day.

The women were among more than 20 bird-watchers who spanned the area around Perry Lake to identify and count birds, statistics that will be provided to the Audubon Society and other organizations to help assess the vitality of bird populations across the country.

As Leo, Walton and Hewins combed back roads near Perry, they said bird counting is an inexact science, at best.

“You have to guesstimate,” Walton, of Topeka, said. “There’s a possibility there are some that get counted more than once.”

But, she said, “It’s amazingly accurate. You miss more (birds) than you would ever count.”

In order to count the birds, bird-watchers keep a sharp eye out for flocks or individual birds, tallying the numbers they see. It’s challenging to get an exact count, because birds are constantly bouncing from tree branch to branch.

Also, birders are limited by geography. Leo, Walton and Hewins drove at a snail’s pace on dirt roads, sometimes hopping out of the car to walk in wooded areas, like the Topeka Audubon Wildlife Preserve, near Perry. They rarely go onto private property, unless they have permission from the property owner.

Still, bird-watching enthusiasts look forward to the Christmas Bird Count, which actually runs for several weeks across the country; this one goes through Jan. 5. It is one of several bird counts conducted throughout the year.

By early Sunday afternoon, Leo, Walton and Hewins had counted more than 30 species, including blue jays, cardinals, purple finches and eagles. Leo, of Prairie Village, has been watching birds for about 20 years; Hewins, of Overland Park, has been on the scene for about 15 years; and Walton, 10. Their tools for attracting and finding birds have changed with the times. On Sunday, they carried high-powered binoculars and an iPod with tiny speakers, with which they played bird calls.

“You don’t realize all these birds exist,” marveled Walton, after the group recorded a golden-crowned kinglet. She said it’s typical to observe 80 to 90 species during a day. Last year, 94 species were seen around Lawrence, according to the Audubon Society.

What originated as a way to preserve wildlife has led conservationists to learn more about how bird populations are coping with human encroachment.

“I think it’s kind of indicative of how we’re doing environmentally, overall,” Hewins said.