These lucky breaks are related in that they assist waterfowl in overcoming the greatest threat to nest success: predation. Of the egg-eating predators that affect nesting waterfowl, the red fox is enemy No. 1. Raccoons and skunks simply flush the hen and consume her eggs, but foxes will catch and eat the hen—obviously this leaves no opportunity for re-nesting. Worse yet, most egg-eaters simply eat until they’re full, perhaps leaving a few eggs to hatch, but a fox will cache the eggs, carrying off and burying every one it finds, then resuming the hunt. For these reasons fewer foxes generally equates to more ducks, especially in areas with poor habitat.
Add to the fox decline the record-breaking moisture soaking the PPR and you have the recipe for a duck population explosion. While global-warming alarmists say the prairie is supposed to dry up, we are in the midst of an uninterrupted wet cycle that began in 1994 and peaked (or so Midwest residents certainly hope) with last spring’s severe flooding. The last three years were the wettest in pond-count history for the American PPR, with a record 3.2 million ponds inventoried last spring.
Water does a variety of things to improve nest success and mask what would otherwise be poor nesting habitat. Perhaps most importantly it creates temporary and seasonal wetlands, which are shallower and therefore warmer than permanent lakes and ponds. Invertebrates and wetland plants thrive under such conditions, creating high-protein food for hungry hens.
“A nesting hen produces an egg a day,” explains Devney. He kneels down, lowers a hand into the muck and when he raises it several snails and a freshwater shrimp flit about in his palm. “She needs food resources to be successful.”
Well-fed hens not only lay healthier clutches of eggs, they’re better able to re-nest should a predator destroy their initial efforts. A malnourished mallard hen may only muster one nesting attempt, but in wet years she may re-nest up to a half-dozen times.
Hens also are territorial creatures. Once she claims ownership of a pond, her drake will vigorously defend it from members of the same species (hens apparently do not perceive other species as competition). The hen guards her entire patch of water whether it’s a tiny pothole or larger permanent pond, which points to another benefit of seasonal wetlands: Nesting hens can pack more densely into an area with numerous small potholes than one with a few large, permanent ponds.
This phenomenon, known as “territorial capacity,” has been studied extensively by Delta Waterfowl. In a study of radio-tagged ducks, Delta found that several young mallards initially attempted to nest in the U.S. PPR. Finding the area at peak territorial capacity, the hens were forced north to Canada. And this was during a wet period with many available ponds! Just think what may happen during a normal or even a dry precipitation cycle. It’s theorized that territorial capacity of the U.S. prairie would decrease, perhaps substantially, and a great number of hens would be forced to nest in Canada where the odds are stacked against them. The fact that the Canadian side of the prairie has underperformed so severely even in this unprecedented wet cycle indicates just how bad its habitat situation truly is, and in a dry cycle it would further devolve and likely host a greater number of ducks bumped from the United States. If Canada’s habitat crisis is not addressed before then, the resulting crash could quickly exceed the 17-year boom.
Wet cycles also benefit duckling survival. During years of heavy precipitation and snow melt, potholes expand into surrounding cover, providing places for ducklings to hide from their top predator: minks. In dry years, ducklings are exposed as ponds recede toward the middle of the bowl.
The Predator Dilemma
“In habitat like that, it doesn’t take long for a single fox to wipe out every egg on a quarter section of farmland,” Devney says.
Habitat declines make it easy for predators to make a living, but we have more than just a wetlands conservation issue on our hands. Many key waterfowl predators are now found well outside their historic ranges, which takes a heavy, unnatural toll on nesting ducks. Raccoons, for instance, weren’t found in prairie Canada prior to the 1950s. Perhaps not coincidentally, that’s also the decade in which populations of mid-continent white-winged scoters—now practically non-existent—began to dry up. The spread of raccoons is attributed in large part to the presence of human homes, which better enables them to survive in bitter cold.
The spread of most other waterfowl predators can be attributed to the removal of larger predators such as grizzly bears and wolves from the landscape. Grizzlies and wolves had a negligible impact on ducks and kept fox, skunk and coyote numbers in check.
Consequently future waterfowl conservation strategy must address habitat declines as well as the accidental introduction of predator species. We should continue focusing our primary efforts on the protection of as much quality habitat as possible, but can that be our only goal? What if grassland losses prove ongoing? And what about the millions of acres of PPR in which booming predator populations already have the upper hand? Delta Waterfowl argues we need a contingency plan, and the only realistic solution is an intensive predator management program.
“If we only had sufficient CRP and grassland habitat, trapping predators wouldn’t be necessary,” says Devney, “but that’s not the reality. If your goal is to maximize duck production, you’re going to have to trap.”
Delta Waterfowl has been instrumental in studying the effects of predator control. Last year in a study conducted across 82 square miles in Manitoba, two trapped nesting sites experienced 43 percent nest success vs. just 3 percent success on the control sites. Overall Delta’s studies show an average two- to three-fold increase in nest success over areas as large as its 144-square-mile site north of Bismarck, N.D.
Devney and I discover many predator-ravaged nests during our tour of the prairie region, raccoons often the likely culprit.
“I’d rather Delta was known as the group that fixed conservation policy in the U.S. and Canada instead of ‘the group that traps,’ but for now we’re happy to work on both,” he tells me as we pore over the remnants of broken shell and yolk.
Critics, however, argue predator management is ineffective and too expensive for widespread implementation.
“We don’t think the benefits of predator management have materialized,” says Mike Checkett, Ducks Unlimited media relations biologist. “It’s an argument we think has been settled by science. On a localized level you can have some impacts, particularly if it’s a closed population like on an island, but in other areas more predators will just move in and need to be trapped again. For waterfowl managers who want to have a wide-scale impact, predator management isn’t a responsible use of limited resources. One study showed you have to spend $300 on trapping to produce one duck. The best use of dollars is habitat work.”
Clearly Delta and DU don’t always agree on the science, but they share the goal of benefiting waterfowl. Surely there is middle ground here. For instance, both agree that habitat conservation is the top priority, and DU has proven itself highly effective in securing wetlands easements. However, for areas in which DU-style conservation or CRP fails, Delta’s predator-management program warrants consideration by state, federal and private waterfowl managers.
“If we keep losing upland nesting cover, primarily through cuts to CRP, we’re going to reduce the capabilities of nesting ducks,” Devney says, “the bottom could fall out of this thing in a hurry.”