By Mike Anderson, Ph.D.
Assessing and adapting conservation strategies helps improve our management of North America's ducks
The prairie wind pushes back wet and cold under the slate-gray April sky as Frederica DeZeeuw trudges steadily back toward the truck, half a mile away. Her chest waders, grown to twice their normal size with mud, suck noisily with each step through the sodden field.
Nestled in the net bag under her arm, a mallard hen and her mate rest, no doubt thoroughly confused about what has happened since they swam into the strange wire cage where another mallard hen sat waiting. Soon to be an actor in the largest play ever devised by waterfowl scientists, for now, the hen rests quietly under the arm of the straining two-legged "predator."
Back along the road, parked on a field approach, waits a pickup camper-Ducks Unlimited's own version of a M.A.S.H. unit. Inside, out of the piercing wind, Bob Emery, DU biologist and accomplished duck surgeon, is finishing with the morning's first patient. As the respirator starts to blow oxygen without the anesthetic, the bird begins to stir.
The 20-gram radio transmitter-now securely sutured inside the hen's abdomen, away from the ovary swelling with the promise of eggs-is already beeping the signal that will allow biologists to follow her fate for as long as she remains in the Beaver Hills.
Far from DU's corporate headquarters or the comfortable malls of a university campus, these researchers labor for back-to-back, 16-hour days in this lonely place because that is the only way to do their jobs well. Nesting ducks don't take weekends off in the springtime. Bob, Frederica, and 12 other dedicated young biologists are here in the pothole-rich hills of east-central Saskatchewan because of DU's commitment to science-driven conservation.
Science Helping to Guide Conservation Programs
Ducks Unlimited relies on scientific studies to help guide its conservation programs because it is crucial to direct hard-earned dollars toward actions and places that will be most beneficial to the birds in the long run.
Ducks Unlimited is committed to the principles of adaptive management, in essence, the continuous improvement in management performance in the face of uncertainty. Duck managers make decisions all the time with imperfect information. That's normal; so do doctors, judges, psychiatrists, CEOs, and stockbrokers.
The way to ensure that DU stays on the right paths is to learn from what we and others do on the land. DU views conservation planning, implementation, and evaluation as a continuous cyclical process where, at each iteration, we have the opportunity to learn and improve our conservation actions.
The Prairie Habitat Joint Venture (PHJV) assessment study is Ducks Unlimited's largest single commitment to biological evaluation. Why? Because DU invests some $25 million each year in work designed to improve the production and survival of breeding ducks on the prairies.
Thankfully, DU's partners in the joint venture and the North American Wetlands Conservation Council also recognize the vital nature of this work. Without their support, DU would not have been able to tackle this ambitious project. But the PHJV assessment is only one of dozens of studies undertaken for the same basic reason.
A few examples: DU-sponsored researchers from Mississippi State University have evaluated how flooding rice fields in winter improves water quality, controls agricultural pests, and, simultaneously, provides foraging habitat for wintering ducks and other waterbirds.
In California, DU-funded researchers have learned how to optimize winter water management to benefit a wide array of water birds. In the Missouri Coteau of North Dakota, a team of scientists from Montana State University is examining the effects that land-use composition, including annual cropping, grazing, and Conservation Reserve Program application, has on duck production.
In southern Saskatchewan, experimental delivery of fall-seeded cereal crops (fall rye, winter wheat) in pothole country revealed good nesting results for northern pintails and other ducks. Wherever DU managers need better information on which to base conservation decisions, DU biologists and their research partners are there, working to lift the fog of doubt.
The PHJV assessment, however, is DU's most ambitious evaluation project. Conducted on 27 individual 25-square-mile landscapes across western Canada between 1993 and 2000, the study has greatly increased our understanding of dabbling duck biology and the responses of ducks to conservation projects. Since the study began, more than 3,500 radio-marked mallard hens have been followed through a breeding season by nearly 250 young biologists.
More than 14,000 duck nests have been found. Some 900 mallard broods have been followed to fledging, and over 54,000 wetlands have been mapped and classified. All the while, researchers persevered, breaking only three bones, wrecking only three trucks, and accidentally burning down just one abandoned farmhouse!
The assessment study was designed to accomplish three things: a) determine the biological effectiveness of prairie habitat programs; b) search for ways to improve these programs in the future; and c) test the major assumptions and parameters in the computer-planning tools used to plan prairie conservation programs. Annual feedback on these questions has been provided to PHJV managers, but recently, as the number of completed study sites has grown, researchers have been able to provide advice with greater confidence.
Some Observations and Surprises
As with most successful research projects, the assessment has produced some interesting observations.
- Choice of nesting cover - On study areas analyzed to date, nesting mallards chose shrubland and woodland as nesting sites in preference to all other cover types. Idle hayland and idle pasture were next, followed by planted nesting cover, wetland edges, and grassland.
Previous research in the Dakotas found that planted cover was most preferred. This contrasting result has major implications for habitat retention and restoration in the northern Canadian prairie parklands (habitat composed of aspen, shrubs, and small patches of grass).
- Nesting success-On most sites, nest success was greater from conservation-treated habitats than all other habitats combined. Generally, nest success was highest in planted nesting cover. The differences, however, between treated and untreated areas were not as great as predicted at the outset.
Within study sites, the likelihood of a nest hatching varied by habitat type, duck species, nest initiation date, the size of the cover patch, the distance of a nest from the edge of a cover patch, and the distance of nests from a wetland.
- Hatched nests by habitat type - For mallards, hatching rates (hatched nests/acre) for idle parkland and planted nesting cover are similar and substantially higher than for any other cover types. Analyses for other duck species are underway.
- Hen mortality - On average, 25 percent (within a range of 15 to 46 percent) of radio-marked hens, mostly birds with active nests, die during the breeding season.This grim statistic surprised us and spurred increased attention to actions that might reduce summer hen mortality. Unlike in the Dakota grasslands, where foxes are the main killers of nesting ducks, red-tailed hawks and great horned owls also are important predators in Canada's parklands.
- Duckling survival - Annual duckling survival averages 54 percent (within a range of 32 to 69 percent), higher than expected, but more variable from place-to-place and year-to-year. Most deaths occurred in the first week of life. Ducklings hatched early in the summer survived better than those hatched later, as did birds from nests closer to water and in areas with more concentrated wetlands.
Adapting Conservation Programs
DU has already made dozens of changes to how it delivers conservation programs on the prairies in response to information emanating from this study. Where planted nesting cover was once created in many pothole-rich areas, now it is more carefully targeted for application to landscapes where it can add acres to areas already rich in perennial cover.