Fine nets are strung in the morning, then the crew sits back and waits for that day's catch.

It's not fish they're after -- it's birds.

Every week, volunteers at Carpenter St. Croix Valley Nature Center in Hastings string nets and wait for birds to fly into them. It's the first step in the process of bird banding.

The scene is repeated weekly at hundreds of banding sites nationwide. Birds are captured and fitted with a numbered metal band, which acts as an identification bracelet. The bird's band number and information about its location, species and age are stored at the federal Bird Banding Laboratory. The next time the bird is captured, its number links researchers to data about its longevity, migration routes, even the health of its population. In fact, the information we have about the migration patterns and longevity of specific species is derived from banding.

Serious, not sport

A black-capped chickadee hits the Carpenter nets. It loudly makes its displeasure known as a volunteer runs to the net, carefully extricates the bird from the tangle, then brings it indoors to be fitted with the leg band it'll wear for the rest of its life. Within five minutes, the chickadee is back outside, none the worse for wear.

During the next several hours, lightweight bands are placed on the right leg of a house wren, a chipping sparrow, a white-breasted nuthatch, a gray catbird, a downy woodpecker and a northern cardinal, among others. (This is a good representation of the birds in the area on a late summer day.)

Catching birds is not taken lightly by either the banders or the U.S. Fish and Wildlife Service. Volunteers continually patrol the nets so they can retrieve birds quickly, minimizing their discomfort and keeping them safe from predators, who'd like nothing better than to find some easy prey. For its part, the wildlife agency grants permits only to banders who have gone through extensive training.

Harvesting information

Researchers are hungry for the kind of information that banding provides. The ever-growing national database has allowed researchers to answer a host of questions: Does this species tend to spend winters in the same area each year? How widely is it distributed over a given area? Is its population healthy or showing a downward trend?

"We've been banding for 28 years now and we're starting to get some significant data," said Jim Fitzpatrick, Carpenter's executive director and a master bander. "We've caught the same white-breasted nuthatch 27 times, which tells us something about its longevity."

But bird banding is also a way for dedicated volunteers to get up-close experience about the birds around them.

"I'm so used to looking at birds at a distance through binoculars, so when I have one in hand I can learn things about its plumage and molting," said Tom Bell, a retired high school biology teacher and a Carpenter volunteer since 1992.

Bonnie Sample is a new volunteer who recently earned a master's degree based on prairie bird research. Sample said she enjoys releasing the banded birds and "contributing to our knowledge about populations and distribution of bird species."

Little bird, long distance

Some of the birds temporarily captured in the nets are year-round residents, such as the downy woodpecker. Others are migrants, caught as they pass through in spring and fall. Migratory birds that end up in the nets several times over the seasons provide a wealth of information.

"The tree sparrows and juncos are the most interesting," Fitzpatrick said. "They spend their summers breeding in the Arctic, and then return in winter. Some we've caught two or three times over the years, which shows how dedicated they are to a wintering site."

A dark-eyed junco banded at Carpenter one February was recaptured the following spring in Alaska, "probably our longest North American encounter," said Fitzpatrick.

Because the junco had been banded and its locations noted in the database, Fitzpatrick and his team knew that this little bird had traveled 3,500 miles to its nesting grounds and the same distance back to Carpenter each year.

If you'd like a glimpse into the fascinating world of bird banding, visit Carpenter in the morning of the fourth Friday of each month. Volunteers band all year long and the banding demonstrations are free, but donations to the center are appreciated.

Val Cunningham, a St. Paul nature writer, can be reached at