Delta's 2003 Predator Management Results
Posted on 09/17/2003
BISMARCK, ND- Delta Waterfowl just completed its 10th and most successful year of managing predators on the prairie breeding grounds.
"Nest success on our predator blocks was off the charts this year," says Delta's Vice President of Operations Rob Olson. "At our Cando site in northeastern North Dakota we had a record 80.22 percent nest success. We managed predators on 36 square miles, and 80 percent of all the nests were successful. That's outstanding, and it's consistent with our long-term results showing predator management increases nest success rates by 200 to 300 percent."
Scientists say nest success across the prairie breeding grounds slipped to 10 percent in the 1990s, well below the 15 to 20 percent rate necessary for the duck population to expand. Research has shown that mammalian predators are the major cause of nest failures, which is why Delta has undertaken large-scale predator management.
Delta began studying the impact of predator management on duck production in 1994 when it hired a trapper to remove predators from a 16-square-mile block of land in the drift prairie of eastern North Dakota. The results were so impressive that Delta has expanded its efforts each year since.
In 2003 Delta had six 23,040-acre sites, all of them located in North Dakota. At Rock Lake, nest success was 57.98 percent, while a "control block"- an adjacent area where predators were not managed-reported a respectable 22.26 percent nest success.
At Delta's Pleasant Lake predator site, 42.38 percent of the nests were successful, while at the Iowa site 42.7 percent hatched (the control block for those sites had 22.87 percent nest success).
The Lostwood predator block enjoyed a whopping 65.22 percent success while the control block was just 10.9 percent. At the Arrowwood site, the predator block had 37.52 percent nest success and the control block had 32.78 percent success.
If nest-success results from Delta's North Dakota predator sites were encouraging, reports from research projects in the Minnedosa area of southern Manitoba told a dramatically different story.
"One of our students, Dan Coulton (MS, University of Saskatchewan), is conducting ongoing research in the Minnedosa area. Dan's preliminary results showed Mayfield nest success for upland-nesting ducks was just 1.9 percent. That's what we call a 'population sink', which means more ducks arrive in the spring than migrate south in the fall."
Olson says the poor results from Minnedosa weren't surprising. "Research has shown that puddle ducks like mallards, teal, pintails and gadwall need very large blocks of grass nesting cover to be successful, and unfortunately most of prairie Canada doesn't have a lot of grass," he says.
Managing predators isn't the only way to offset the impact of predators in fragmented landscapes. Artificial nesting structures, like Delta's Hen Houses, also can be highly effective, as evidenced by the 40.7 percent nest success for mallards using Hen Houses in Coulton's study area.
"Nesting ducks need relief from the growing number of small predators like fox, raccoon and skunk," says Olson. "Where waterfowl management doesn't have the dollars to put millions of acres of nesting cover on the ground, predator management and Hen Houses are great ways create secure nesting sites.
"In many areas of the pothole region, managing predators and putting up Hen Houses are the best ways to increase nest success," says Olson. "Waterfowl management needs to protect every square inch of habitat it can, but research has shown that ducks need 40 percent of the landscape in grass nesting cover if they're to be successful. Putting 40 percent of the pothole region into grass nesting cover simply isn't socially, politically or economically realistic.
"Where management doesn't have the dollars to impact the landscape on a large enough scale, other management tools are necessary, and predator management and Hen Houses are two of the most effective tools at our disposal."
Olson says production this spring should be much better than it was a year ago, and adds that some areas of the country will likely enjoy improved hunting this fall. "As always, a lot depends on local conditions, which can vary greatly, and on the weather.
"I'm guardedly optimistic about the coming season," Olson says. "The breeding grounds got wet last spring, which is good. But for the first time in years, most of the ducks settled in prairie Canada. Because Canada doesn't have a grass set-aside program like the Conservation Reserve Program here in the US, there's some question as to what kind of production we'll see.
"Most of the reports we've been getting are positive," Olson says. "The fall flight should be better than a year ago, but whether or not it will produce the 'banner season' some are predicting remains to be seen."