Dr. Roger Strand spent his professional life healing people. He has devoted much of his free time helping rejuvenate Minnesota's wood duck population.

"Just look at a drake wood duck," he says admiringly. "It's such a beautiful animal."

With iridescent chestnut, green and purple plumage, accented in white, it's one of nature's the most spectacular specimens. And for more than a half-century, Strand has been one of its most passionate champions.

A well-known conservationist and member of the Wood Duck Society, Strand, of New London, has erected more than 100 wood duck boxes over the years on his 400-acre farm and nearby, including a local school and environmental learning center.

Though too modest to admit it, Strand, 76, has become an expert on the species and on wood duck box placement, and is an institution in the New London area. For more than 30 years, the local chapter of the Minnesota Waterfowl Association has held Prairie Pothole Day on his farm, attracting up to 5,000 people each September.

Over the years, Strand's wood duck boxes have introduced scores of elementary school children to nature. And the cedar boxes have spawned lots of wood ducks.

"Those boxes produced 13,000 ducklings over the past 20 years," Strand said Saturday at the Minnesota Waterfowl Association's annual waterfowl symposium in Bloomington, where he recounted his efforts. He has kept meticulous records of the success -- or failure -- of each box.

"Those aren't paper ducks or computer ducks, they are real," said Strand, referring to typical waterfowl population estimates done through modeling. The use of wood duck boxes has flourished around the nation since the wood duck population collapsed by the early 1900s from habitat loss and overharvest.

"Some of us feel like this is a real contribution, not just a rinky-dink hobby," Strand said. "The numbers add up."

Besides, he said, "It's fun and rewarding; I love to do it."

Strand, who retired as a surgeon 20 years ago, uses his wood duck houses to teach ecology. Kids can stand on a stool and peer into an occupied wood duck house.

"They love it, you can see it in their eyes," he said. "You can talk to them about habitat, clean wetlands, what the ducks eat and why they want to nest here."

His passion -- some might call it an obsession -- with wood ducks began as a youngster. He grew up in Minneapolis in a hunting family, and spent summers on Green Lake near New London, where his father grew up. His dad eventually bought 80 acres nearby "so the family would always have a place to hunt," Strand said.

Later, Roger Strand added to the acreage and now lives there with his wife, Kay, still hunting waters that he first hunted in junior high. He erected his first wood duck box there in 1956.

"I thought we had to do something," he said. "The newspapers talked about wood ducks coming back from the brink of extinction, and you could help them by putting up boxes."

So he did, one after another. Ten years ago, the tally hit 100.

But over the years, Strand learned what worked and what didn't. Wood duck boxes nailed to trees were death traps.

"I found a dead hen in a box, and a gray squirrel was still in there with its litter," he said. "That taught me a lesson."

He learned that legendary Illinois waterfowl biologist Frank Bellrose, a pioneer in waterfowl management, recommended metal guards to prevent predators such as raccoons, mink and squirrels from destroying eggs and ducks.

Placed on a post away from low-hanging branches and with a metal predator guard, the boxes offer wood ducks safe nesting.

Strand got religion, and now he spreads the gospel.

"For over 30 years since I started using predator guards, I've had no mammalian predation of wood ducks in a box," he said.

And with the predator guards, the boxes can be placed just a few feet from the ground, making them safer to install and easier to check, clean and observe ducks and ducklings. Strand builds his own wood duck boxes from cedar, and his local Waterfowl Association chapter helps market the metal guards.

He still hunts, though he passes on wood ducks now, afraid he might shoot a hen from his boxes. He urges hunters to shoot drakes and leave hens.

"Why not take the drake and let her come back and produce 14 more ducks?" he asks.

He's skeptical about the decision by state officials in 2011 to increase the daily wood duck bag limit from two ducks to three.

"It remains to be seen if that will affect the breeding population in Minnesota," he said.

Regardless, Strand continues to preach the values of wood duck houses.

"It's a lot of fun, it makes a difference -- and it gets kids outdoors," he said.

Doug Smith • dsmith@startribune.com