Maximizing Duck Production

Waterfowl scientists and managers are keenly attuned to nest success as a key measurement of breeding ducks. Rightly so, because nest success—the percentage of individual nests that hatch at least one egg—is the primary driver of duck production as long as the prairies are wet. 

It’s generally well accepted that 15 to 20 percent of duck nests need to hatch to maintain the population at its current level. 

Yet another metric that biologists use could be even more important to measure duck production: Hen success. 

What’s the difference? 

Hen success is the percentage of hens that hatch a nest during one nesting season. 

But are we just splitting feathers here? 

Nest success and hen success are closely related, but they’re not the same. Consider that many hens, if their first nest attempt fails because of predation, flooding, or another disturbance, will try again. She will find a new location, form another nest bowl, and lay another clutch of eggs. Biologists call this behavior “renesting.” 

Let’s use a single hen mallard in Saskatchewan to illustrate the difference between nest success and hen success. Our hen’s first nest was discovered by a raccoon after she began incubating 11 eggs. The raccoon chased our hen off and ate all of the eggs. The hen started a new nest in taller cover, but a skunk found her eggs after she’d laid five of them. Our resilient hen picked a new spot and laid seven eggs. Her third nest was far from a predator travel lane, and after 26 days of incubation, seven ducklings hatched. Our mallard’s nest success was only one out of three, while her hen success is one of one, or 100 percent. If you measure the hen’s breeding result on her first or second attempt, she failed. But because of renesting, our hen succeeded in adding ducks to the population. 

The Power of Predator Management 

When nest success is extremely low, such as 5 to 10 percent, hen success is going to be similarly low, according to Mike Buxton, waterfowl programs director for Delta Waterfowl. Predation is the No. 1 cause of nest failure. In habitat with an overabundance of predators—such as raccoons, skunks, and other mammals—when there’s not enough nesting cover, renesting attempts fail at a high rate. 

Conversely, when nest success is high, such as above 40 percent, hen success will also be similarly high. Habitat that produces high nest success doesn’t require ducks to renest, so the rates of nest success and hen success are similar. 

“In the middle ranges when we see 20 to 40 percent nest success, hen success can really accelerate when water conditions are good later into the spring and predator numbers are under control,” Buxton said. “These are the areas where Delta’s Predator Management work can really boost duck production.” 

Research shows that nest success on Delta’s upland Predator Management blocks averages 34 percent. Applying calculations derived from the study “Mathematics and Mallard Management” by Lewis Cowardin and Douglas Johnson of the U.S. Geological Survey’s Northern Prairie Wildlife Research Center, hen success jumps to a phenomenal 52.8 percent. So, more than half of the nesting hens that choose to lay eggs where Delta is conducting Predator Management will hatch their nests. The average nest contains nine eggs, and half of the ducklings will survive to fledge (fly). 

“Our Predator Management work is increasing both nest success and hen success, and producing a lot of ducks,” Buxton said. 

The Queen of Renesters  

Mallards are the most adaptable and abundant duck in North America, so it makes sense that they are prolific renesters. 

Not all duck species will renest. Gadwalls, pintails, and shovelers are known to try again if their first nest is lost, while later-nesting ducks such as blue-winged teal and canvasbacks are usually one-and-done. 

“As long as the landscape has good water, mallards will keep trying to nest,” said Dr. Frank Rohwer, president and chief scientist for Delta Waterfowl. “Data shows that some mallards will attempt up to six nests during a breeding season, and most hen mallards renest repeatedly if predators get their eggs.” 

However, each attempt comes at a cost for duck production. 

“The first nest a hen makes is always the most productive attempt,” Rohwer explained. “The value of each renesting attempt decreases because they lay fewer eggs each time. Also, ducklings hatched later are often at a disadvantage because the preferred shallow ponds often dry out later in the summer.” 

In addition, each day on the nest increases the likelihood that the hen will die in the teeth of a predator. A comprehensive study of marked mallards largely conducted by biologists in Canada found that 23 percent of hen mallards were killed by predators during the three-month nesting season. By comparison, fewer than 1 percent of marked drakes died during the same period. Clearly, sitting on eggs is dangerous for hens. 

Renesting effort, even for mallards, depends on habitat conditions. Abundant shallow wetlands that provide nutrients for the hen’s body to form eggs is key. 

“In drought years, even the mallards may not renest,” Buxton said. “When conditions are poor, nest success and hen success will both be low.” 

When water conditions are good, ducks that renest have a better chance to hatch on their second attempt. Buxton explained that during the middle of the prairie nesting season (late May/early June) the cover has grown taller and thicker, predators have more food options, so they’re less likely to prey on duck nests, and there are simply more ducks nesting. 

“Maybe not the first nest, but on their second or third try, they’re likely to hatch a successful nest if there’s good water and not as many predators on the landscape,” Buxton said. 

Critical Support for Ducks 

Increasing nest success and hen success on the prairie breeding grounds is Delta’s primary goal. Deploying proven duck production programs—Predator Management and Hen Houses—will result in more hens successfully hatching nests. 

In 2022, Delta Waterfowl embarked on a bold, ambitious $250 million fundraising initiative—The Million Duck Campaign—to create an endowment fund that will deliver 1 million ducks annually to the fall flight. 

The Duck Hunters Organization will scale up its proven duck production programs to put more ducks into all four flyways. Strategic installation of Hen Houses will take the mallard-producing program to 110,884 nest structures across the PPR, while also scaling Predator Management to 366 sites. The result is the annual production of 1,000,660 ducks. 

“The Million Duck Campaign will support Delta’s work across all four critically important pillars: habitat conservation, research and education, HunteR3 and of course, duck production,” said Dr. Scott Petrie, chief executive officer of Delta Waterfowl. “We want to lead waterfowl management into a new era where we measure success by our contributions to the fall flight.” 

Legions of conservation-minded donors have embraced and supported Delta’s Million Duck Campaign. In addition, industry-leading companies such as Benelli immediately stepped up to back MDC. Benelli has long been a top industry partner and valued corporate sponsor of Delta Waterfowl and the organization’s mission to produce ducks and ensure the future of waterfowl hunting. 

Ultimately, boosting Delta’s duck production efforts to maximize the available breeding habitat will result in 1 million additional ducks in the fall flight each year. 

All of us at Delta Waterfowl and Benelli—along with every hunter who totes a shotgun to the blind—want more ducks over the decoys. 

Delta Waterfowl is The Duck Hunters Organization, a leading conservation group working to produce ducks and ensure the future of duck hunting in North America. Visit deltawaterfowl.org.