Prime grounds for waterfowl research

[webfoot]

Prime grounds for waterfowl research

Predator-trapping site puts N.D. prairie at forefront of duck studies

By Brad Dokken
Herald Staff Writer

CANDO, N.D. - A 10-year project to trap predators on a federal Waterfowl Production Area northwest of here has had a dramatic impact on local duck nesting success. Now, a series of research projects aims to learn more about what that success means to the overall density of ducks in the area, nesting success outside the trapping sites and whether the predator work has aided shorebird populations.

There's also a study under way to explore why lesser scaup, or bluebill, populations in the trap area are flourishing when the species is in decline across North America.

Most of the work is centered on the Nikolaisen Waterfowl Production Area and adjacent lands. Delta Waterfowl is funding a majority of the research.

"I can't think of an area quite like this where we've had so many different projects over the years," said Frank Rohwer, a wildlife professor at Louisiana State University and scientific director of Delta Waterfowl. "In terms of ducks, this is pretty unique."

Rohwer, who serves as advisor for several of the student projects, spends his summers in Egeland, N.D., to be near the research sites.

High nest success

The phenomenal duck nesting success on the Nikolaisen WPA dates back to the mid-'90s, when Delta Waterfowl and a handful of partners launched a project to trap predators such as skunks, fox and raccoons from a series of blocks within the area. The project initially covered 16 square miles, Rohwer said, and later expanded to 36 square miles.

The result, Rohwer says, has been nesting success on the Cando block of about 80 percent - far above the 15 percent to 20 percent level biologists consider necessary to sustain duck populations. While predator trapping is a controversial management tool, Rohwer says there's no question it's effective at boosting nesting success in areas where the crucial ingredient of quality habitat also exists.

"Given the controversy, people want to know, 'How many ducks can you produce? How effective is trapping?'" Rohwer said.

That's what one research student hopes to find out.

Matt Pieron, a graduate student at LSU, is studying the concept of "density dependence" - how many ducks a specific area can support. As part of the project, Pieron and a staff of 14 student assistants are monitoring more than 4,000 duck nests to study everything from the size of individual eggs, to the size of the brood and the density of nests in a given area.

Down the road, Rohwer says Delta researchers also hope to purchase 300 radio-transmitter collars to fit on mallards. Each collar costs about $200.

Unique site

The project covers six trap sites of 36 square miles each and four non-trapped "control" sites of the same size. Such research isn't possible just anywhere, Rohwer says, because few areas support such high populations of nesting ducks.

"The question is, how many ducks can you put in an area before they get in each other's way?" Rohwer said. "I can't tell you how many people are really excited about this. Nowhere else in North America have we done work on a local scale where we're really going to have an impact on populations."

Pieron says the research is "a bit daunting" because it covers such a large area. It's too early to draw any conclusions, but someday, Pieron says, he hopes waterfowl managers can use the results to make management decisions that benefit ducks.

Scaup buck trend

Research on the prairies of North Dakota also could help unlock the mystery of declining continental scaup populations.

When the predator work started in 1994, Rohwer said, researchers didn't find a single scaup nest on the trapping site. "Now you can find a whole bunch," he said. "The scaup population has just gone through the roof here."

Curt Francis, a graduate student at North Dakota State University, is studying why scaup on the research site are doing so well when they're declining nationally.

Researchers have attributed the national trend to scaup being in poor physical condition when they arrive on the nesting grounds. But if that's the case, Rohwer says, why isn't the same trend apparent near Cando?

Francis is studying both adult and juvenile scaup, measuring their nutritional condition and taking blood samples to see if hormones play a role in reproductive success. He also is fitting ducklings with a special band lined with plasticine, a clay-like substance, which wears off as the bird grows.

Scaup return to the same breeding areas every spring, so the findings eventually could shed light on what's happening with the continental population.

"Right now, it's a cool population to look at. It's just grown so dramatically" on the research site, Rohwer said of scaup numbers. "There are so many ducklings here, (Francis) will have a hard time looking at all of the marked ducks."

Scaup researchers everywhere wish they had that problem.

"I would like to produce a plot of how many nests there are," Rohwer said. "It's really gone up dramatically."