They don’t venture forth by the thousands on “opening day.” They don’t have to buy licenses or complete any kind of safety training to pursue their pastime.

They’re bird-watchers, or birders. They’re out there. They’re just invisible to us.

Minnesota and Wisconsin can boast more birders than all but two other states in the nation. Birders, both homegrown and those who come to visit, contribute more than $412 million annually to Minnesota’s economy, based on a 2001 survey by the U.S. Fish and Wildlife Service.

Birding expenditures are close behind the $467 million that hunters spent but far behind the $2.5 billion that anglers spent in 2001.

Birding is the most popular form of wildlife-watching in Minnesota and has enjoyed steady growth since the early 1990s. More than 1.4 million birders, residents and nonresidents, pursued their hobby in Minnesota in 2001.

The birding figures are part of a larger survey conducted by the U.S. Fish and Wildlife Service to track outdoor recreation trends.

Birders range from the casual “backyard” birders who keep a few feeders to serious birders who will travel widely and often keep detailed lists of birds they’ve observed.

“As we become more and more urbanized, more and more pulled away from the natural world, we still need nature in our lives,” said Duluth birder Laura Erickson.

“It gives you an eye on nature,” said longtime Duluth birder and former National Aubudon Society board member Jan Green. “It takes you away from the affairs of the world, or your personal affairs, and opens up a world you’re not in control of. It’s kind of this spiritual, God-created-the-universe kind of message.”

Birding appeals to people on several levels, Erickson said. The collectors among us can keep lists of birds. Backyard lists. County lists. Minnesota lists. Lifetime lists. The intellectuals enjoy learning birds’ habits and natural history. And most of us simply enjoy looking at birds and watching them fly.

“They appeal to something deep in the human soul,” Erickson said.

It doesn’t hurt that they are all around us, that we can watch them from inside our homes and that even serious birding requires little special equipment. A pair of decent binoculars and a good birding guide are the essentials.

Most birders can recall a single moment that opened their eyes to the world of birding, Erickson said.

“Usually there’s a magic moment that sparks it,” she said. “Somebody will see a bird that is either so beautiful or doing something that seems so strange, and it will ignite something.”