Gazette photos by Andrew Wallmeyer When Xcel Energy's Allen S. King Plant became the first such facility to put a nest box on its stack 20 years ago, there were only three pairs of peregrine falcons nesting in the state. Since then, the King Plant nest has produced more than 50 peregrine offspring.

OAK PARK HEIGHTS - For Bob Anderson, heading halfway up the 800-foot stack at Xcel Energy's Allen S. King Plant to check on a family of peregrine falcons, as he again did Tuesday morning, is just another day at the office.

Still, the 20-year-old King Plant nest box has a special place in Anderson's heart, since it was the first of its kind and it became the model for the dozens that followed, which have together hatched nearly 1,000 peregrines in the last two decades.

Peregrine falcons were once so rare that raptor expert Anderson assumed Paul Simonet was mistaken when he called to report a sighting at the plant in 1988. At the time, there were only three known peregrine pairs in the state. When he saw a picture taken by John Miggler, he knew the sighting was real. He soon had permission to put a nest box at the 400-foot level. The rest, he says, is history.

"This unusual and novel marriage of industry and conservation has had a tremendous contribution to the recovery of the peregrine falcon, to the point where it could be removed from the endangered species list," said Anderson, who for the last 20 years has headed up the Raptor Resource Program and is now Xcel's director of conservation.

Peregrine falcons are best known as the world's fastest animal, diving at speeds up to 240 mph when hunting other birds in flight. They can be found around the world, typically along mountain ranges, coastlines and river valleys, and they were removed from the U.S. Threatened and Endangered Species list in 1999.

While the bird's impressive return from the brink of extinction was a tremendous success, Anderson said he and other peregrine watchers weren't content with an entirely urban population. About a decade ago, they started an active campaign to get the birds back on cliffs, where they belong.

"That was the Holy Grail, was to get them on the cliffs," he recalled. "For many years, we had them on a variety of tall man-made structures, but all along everybody's goal was to get them back on cliffs. We had some problems with our initial releases on cliffs. ... For a long time, it looked like we would only have an urban peregrine population."

The breakthrough came when the researchers raised baby falcons in an artificial rock room and released them on cliffs far from any man-made objects. The young birds soon found their way. Once they had established themselves in their new environment, other peregrines - including those hatched on stacks like that at the King Plant - started showing up.

"What happened is we created an activity center - peregrines are attracted to peregrines. Once we had a few birds on cliffs, it just mushroomed," Anderson said. "Once we had some birds on cliffs, then the smokestack birds started interacting with them. Now the crossover is taking place, and we're seeing birds going both ways."

Hearing that, Dan Berger smiled.

Berger, who has tracked peregrines since the 1950s, traveled from Southern California to see Anderson band this year's hatchlings.

"I was fresh out of high school in 1952, and we had just started up a project banding migrant birds of prey - not just peregrines, but everything. Of course, the peregrine was the Holy Grail, because they were so rare," Berger recalled. "Ever since then, I've wanted to see the birds back on the cliffs. To know that now they are, it's wonderful."

On Tuesday, Anderson pulled two male hatchlings from the King Plant nest box, banding them and taking blood samples in front of middle school students from Minneapolis. Last year, he did the same with four birds in front of students from Andersen Elementary.

Anderson said those birds - which the students named Frightful, Croix, Lightning and May - are now nearly mature, with the males likely nesting within 70 miles, and the females within 220.

"I can't tell you off the top of my head where each of them are right now; I'd have to look it up," he said. "At one time I knew every falcon in the Midwest by name, but now it has grown to the point where it's bigger than me and bigger than all of us. It's been a tremendous success story."

Anderson said one of the young males may have moved in with an older woman in the Twin Cities.

"We've got an immature falcon paired up with an adult female at a cliff near Lock & Dam No. 9, and it's possible he came from here last year," he said. "It is kind of fun to see where they go. And inspiring... it's been a great success."