Courtesy of Brad Dokken and the Grand Forks (ND) Herald.

SUCCESS ON THE PRAIRIE: Predator management helps boost duck nesting success across N.D. prairie pothole country

"Nest failure in this part of the world is almost always due to predation. There are places with such low densities of duck nests you can drag a chain all day and find one or two nests.", Frank Rohwer, scientific director, Delta Waterfowl Foundation

By Brad Dokken
Herald Staff Writer

CANDO, N.D. Liz Loos and Frank Rohwer were trying to demonstrate a technique they use to find duck nests concealed in prairie grass, but they weren't getting very far. Duck nests kept getting in the way.

Seated on ATVs connected by a 150-foot length of chain, the two waterfowl researchers were attempting to comb a piece of the Nickolaisen Waterfowl Production Area north of here using a technique called nest dragging. They dragged the chain through the grass, hoping to temporarily roust a nesting hen off her eggs. That would allow them to find the nest, examine the eggs and gather information on everything from nest density in a particular area to nesting success - useful stuff if you're a waterfowl researcher.

In an area of maybe 50 square yards, the husband-and-wife team flushed a half-dozen ducks and found nests ranging from blue-winged teal to northern shoveler and mallards. They used a sawed-off length of radiator hose to candle the eggs, holding the eggs toward the light to check the embryo's development. The pair then marked the location of each nest with a numbered stake and logged the position with a hand-held Global Positioning System unit. They'd come back and check each of the nests seven to 10 days later.

Researcher's dream

For a waterfowl researcher, the Nickolaisen WPA is a dream come true because it's a haven for nesting ducks. That's no coincidence. Through a cooperative effort between the Bismarck-based Delta Waterfowl Foundation and the U.S. Fish and Wildlife Service, a 36-square-mile block that includes Nickolaisen and adjacent private lands is being intensively managed for predators in an effort to boost nesting success. Known as the Cando block, the 23,000-acre site is one of 10 across North Dakota being trapped to remove predators.

The results are striking. Since predator trapping became an annual event in 1999, nesting success on the Cando block has flirted with 80 percent - far above the 20 percent figure biologists often cite as necessary to maintain a duck population. Nesting success in other North Dakota trap blocks has ranged from 38 percent to 61 percent.

According to Roger Hollevoet of the U.S. Fish and Wildlife Service in Devils Lake, removing predators at Kellys Slough National Wildlife Refuge northwest of Grand Forks has helped nesting success reach nearly 60 percent.

By comparison, nesting success on untrapped control sites last year dipped as low as 11 percent. Delta Waterfowl and Fish and Wildlife Service staff recently hosted a handful of outdoor media from as far away as Louisiana to help tell the predator management story. After all, the ducks hatched on the North Dakota prairie are some of the same birds Southern hunters will encounter next fall.

"There's no way we'd be finding this many nests without this treatment on the landscape", said John Devney, vice president of marketing and communications for Delta. "This is just exceptional."

According to Rohwer, a professor of wildlife ecology at Louisiana State University and scientific director for Delta Waterfowl, nesting success across prairie duck country has been on the decline since the mid-1930s. As agriculture and other human influences changed the landscape, predators such as fox, skunks and raccoons gained a foothold. Waterfowl nesting success that used to average about 40 percent now usually is less than 10 percent.

"Nest failure in this part of the world is almost always due to predation," Rohwer said. "There are places with such low densities of duck nests you can drag a chain all day and find one or two nests."

Showing the success

In the Cando block, skunks especially have been abundant this year. Buck Holien, a Cando-area trapper, has trapped more than 200 skunks from the predator block since starting this year‚s campaign in April. He'll typically remove between 300 and 450 predators of various types by the time nesting season winds down in mid-July, Rohwer said.

"These guys are dedicated," Rohwer said of Holien and trappers at other predator management sites. "They'll be out here running their trap line early in the morning, and we'll see them back out here at 9 at night."

According to Rob Olson, director of Delta Waterfowl, predator control fits with the foundation's philosophy of putting two ducks back for every duck that's shot. It's not a cure-all to improved duck production, he said, but it's a way to boost nesting success where improved habitat alone isn't doing the job.

While Delta's focus has been on North Dakota, Olson said the foundation someday would like to expand predator management to other important breeding areas. But for that to happen, he says, duck hunters probably would have to pick up some of the costs. Trapping isn't cheap. Just managing the Cando site will cost about $20,000 this year. That's why it's important to get the word out to hunters and waterfowl managers.

"The support from duck hunters has been tremendous," Olson said. "I'm not surprised by that. They're supportive because (predator management) makes a lot of sense to them. It reinforces what they already know - there are too many predators."

Program has critics

Predator management hasn't been without its detractors. According to Rohwer, Delta's first attempt at predator management dates back to 1994, with a 16-square-mile block near Cando. Critics said it wouldn't remove enough predators to make a difference, but results from that initial study showed nesting success went from 15 percent to about 40 percent. "That turned some heads," Rohwer said.

Delta then expanded the site to its current size of 36 square miles. Rohwer said even the intense trapping in the Cando block isn't enough to remove all of the predators, and new critters will migrate into an area by the next spring. During the recent tour, he found the proof in a northern shoveler nest, where several eggs had been sucked dry by what appeared to be a skunk.

"That's a pretty rare event out here on these trap sites," Rohwer said. "We've gotten kind of spoiled. We don't expect to find many sites with depredated eggs."

In his role as Delta's scientific director, Rohwer has helped oversee several research projects in the Cando area since the mid-'90s. Loos, his wife and partner in waterfowl, got her master's degree from LSU and recently earned her doctorate from the University of Louisiana in Lafayette. She did most of her fieldwork on the prairie north of Cando, and her doctoral dissertation focused on 'nest synchrony' - the mysterious internal clock that tells eggs laid over several days to hatch at the same time.

Loos says her research wasn't directly related to predator management, but it would have been difficult to complete working in an area with poor nesting success.

Here on the Cando trap block, that obviously isn't a problem. "This isn't typical of nesting success on the prairie," Rohwer said. "We'll find more than 100 nests in a quarter (section) on predator blocks. I've been working up here 30 years, and I've never seen anything that comes close."