By David Howerter, Ph.D., and Johann Walker, Ph.D.
It is mid-June in the Boreal Forest of Alaska, and a researcher kneels in the low shrubs along a remote lakeshore to examine a recently hatched nest of a northern pintail. He counts and records five recently hatched eggs. Noticing that the empty nest bowl is somewhat larger than usual, he begins to examine it more closely. After gently pulling apart the stack of feathers and dead vegetation, he is amazed to find the remains of five hatched nests, each one stacked atop the next. He realizes that the same hen likely returned to nest successfully in this exact spot for more years than many ducks live.
Meanwhile, thousands of miles away on the prairies of Saskatchewan, another researcher kneels in a winter wheat field to examine a mallard nest. This is the second nest initiated by a young female after her first was lost earlier in the spring. It contains nine hatched eggs. After recording data about the nest, the researcher tunes her radio receiver to the frequency of a transmitter attached to the young hen. She picks up a signal coming from a nearby seasonal wetland and heads toward it in hopes of getting a look at the hen and her new brood.
For waterfowl researchers, the stories of individual nesting ducks are endlessly fascinating, but the real power of science becomes apparent when information is collected from thousands of birds across vast landscapes. Knowledge gained from this research leads to more effective conservation actions and generates new questions about what can be done to benefit breeding waterfowl. Exploring these questions and evaluating the outcomes of our current conservation efforts allows Ducks Unlimited to adapt and take advantage of new opportunities to deliver our mission more efficiently and effectively.
How We Study Breeding Waterfowl
Breeding pair and brood surveys, nest survival research, and radiotelemetry studies are the mainstays of waterfowl research. Surveys are used to monitor the abundance and distribution of waterfowl populations. The most extensive and longest-running wildlife survey in North America is the annual Waterfowl Breeding Population and Habitat Survey, which has been conducted by the U.S. Fish and Wildlife Service, Canadian Wildlife Service, and other partners since 1955. The Prairie Pothole Region and Western Boreal Forest are the primary focus of the survey. On average, the traditional survey area hosts about 34.9 million breeding ducks. Duck populations in this area have ranged from a low of about 25 million breeding ducks during times of severe prairie drought to highs exceeding 49 million birds during recent years of exceptionally wet weather.
Nest survival research provides precise information about the probability of nests hatching. This research is used to monitor duck nest success across broad landscapes and in different habitat types and regions. Radiotelemetry studies of breeding females allow researchers to monitor individual hens from the time they begin to nest to when their broods fledge. While each of these techniques has strengths and weaknesses, together they serve as a powerful set of tools for studying and developing a better understanding of waterfowl breeding ecology.
What We Have Learned
Several decades of research have given us a clear picture of the factors that drive waterfowl population dynamics. Events that occur during the breeding season primarily determine if duck populations increase or decrease. The proportion of nests that hatch and the number of ducklings that survive to fledging are especially influential on waterfowl numbers. The breeding season is a perilous time for ducks. Hens suffer approximately 25 percent mortality while nesting. In addition, only 40 to 60 percent of hatched ducklings survive to fledge. However, the most important factor influencing duck populations across much of the breeding grounds is nest success (the proportion of duck nests that hatch). For populations to be stable, nest success must average about 12 percent. If nest success exceeds that level, duck populations are likely to increase, while lower nest success rates usually result in declining populations. These factors account for much of the variation that we see in duck populations from one year to the next. In fact, a study led by scientists with DU Canada's Institute for Wetland and Waterfowl Research estimated that approximately 90 percent of the variation in mallard population growth rates was determined by factors on the breeding grounds.
The key ingredient to ensuring that waterfowl can successfully nest and raise their broods is habitat. Wetlands, of course, are a crucial component. Prairie potholes and other wetlands support multitudes of protein- and calcium-rich invertebrates, such as fairy shrimp and insect larvae, which breeding hens need to produce a clutch of eggs. Wetlands also provide vital feeding habitat and cover for broods. Duckling survival is typically higher on landscapes with an abundance of natural wetlands than in areas where wetlands are few and far between. Stated simply, without wetlands there would be no ducks.
However, wetlands are only part of the equation. Most dabbling ducks, including mallards, northern pintails, and blue-winged teal, nest away from wetlands in surrounding upland vegetation—sometimes as far as a mile or more from the nearest water. Thus, adequate nesting cover provided by grasses and shrubs is crucial to both nest success and hen survival. More nests hatch and more hens survive on landscapes with abundant natural upland vegetation.
How We Use the Information
Information collected through scientific investigation doesn't just gather dust on a DU researcher's desk. In fact, we use this data to guide every aspect of our conservation programs. Over the course of the past two decades, we've collected information on nearly 40,000 duck nests across the Prairie Pothole Region. DU has used data collected from this research to develop planning tools that predict how landscape conditions influence waterfowl reproduction. For example, when wetlands are drained, we can estimate how many fewer ducks will likely settle in that area and what impact the loss of wetlands will have on duckling survival among the birds that remain.
We can also estimate the positive impact our conservation programs will have on breeding ducks. When we restore tracts of grassland, we can estimate how many ducks are likely to use this habitat as well as its positive impact on nest success. Moreover, additional factors, such as the cost of restoring wetlands and grasslands in a particular area and the risk of habitat being converted to other uses, are included in our project planning. All this information helps ensure that we receive the greatest possible return on our conservation investments.
How We Conserve Habitat
The Prairie Pothole Region is the most important landscape in North America for breeding waterfowl. On average, three-fifths of breeding ducks settle on the prairies each spring. About 90 percent of the land on the prairies is privately owned working agricultural land. That's why our prairie conservation programs are carefully targeted on the most productive landscapes for breeding waterfowl and provide incentives for farmers and ranchers to protect, restore, and enhance habitat on working agricultural lands.
We've learned that the foundation of prairie duck populations is abundant shallow wetlands. And the more wetlands, the better. Unfortunately, the most valuable wetlands for breeding ducks are also those at the greatest risk of drainage. As global demand for food, fuel, and fiber increases, pressure to drain wetlands grows. Consequently, we are working to conserve shallow prairie wetlands in a variety of ways, including through restoration projects, perpetual easements, term-limited conservation agreements, land acquistions, and public policy. Grassland and other nesting cover, such as fall-seeded cereal crops, are also essential to prairie-nesting ducks, and we conserve these important habitats using many of the same methods that we use to conserve wetlands.
Perpetual conservation easements are the backbone of DU's habitat programs on the prairies. These easements prohibit the plowing of grasslands and drainage of wetlands in exchange for a onetime payment of a percentage of the land value. Landowners retain ownership of their land and can continue to use it for farming or ranching as long as wetlands and grasslands are conserved. Perpetual easements are very popular with private landowners because they protect fundamental habitat values while also allowing producers to access capital that is tied up in the land.
Term-limited conservation agreements typically range in length from one to 30 years. Longer contracts often include the restoration and management of perennial vegetation and wetlands on marginal cropland. In other cases, these agreements provide landowners with incentives, such as assistance with fencing and development of new water sources, to keep land in pasture. Winter wheat and other winter cereals programs provide incentive payments or in-kind donations of seed and other inputs to encourage producers to include these duck-friendly crops in their farming operations.
When appropriate and when none of the other management actions will work, DU may acquire high-priority, at-risk habitats to fulfill its mission. DU's land acquisition work on the prairies is based on a revolving ownership model. DU purchases tracts of high-priority conservation land, restores wetlands and nesting cover on the property, protects the habitat with a conservation easement, and then sells the land—usually to a local farmer or rancher. Land acquisition is an effective way to restore and protect threatened waterfowl habitats when the current owner is not interested in restoration incentives or a perpetual easement. This practice also keeps land in agricultural production, which is important to rural communities. However, land acquisitions are both time- and labor-intensive, which limits the amount of land that can be conserved in this manner.
Public policies that protect wetlands and grasslands on the prairies vary between the United States and Canada and among Canadian provinces. In the United States, conservation compliance provisions in the Farm Bill stipulate that agricultural producers who participate in U.S. Department of Agriculture (USDA) programs, including crop insurance and conservation programs, cannot drain wetlands or farm land with highly erodible soil. Because producers almost always elect to comply with USDA regulations, these disincentives have helped reduce wetland losses on the U.S. prairies since conservation compliance provisions were first included in the 1985 Farm Bill. In Canada, wetland regulations are determined at the provincial level. In Prairie Canada, Alberta regulates wetland drainage, and Manitoba is currently considering similar regulations. Although wetland losses in Alberta have been slowed by these regulations, wetland drainage remains a serious problem in Saskatchewan and Manitoba.
Located just to the north of the Prairie Pothole Region, the Boreal Forest is North America's second most important waterfowl breeding area after the prairies. Spanning more than 1.5 billion acres from Newfoundland and Labrador in the east to Alaska in the west, this vast region supports approximately 40 percent of the continent's breeding ducks on average, and an even larger proportion of waterfowl settle here when the prairies are experiencing drought. As on the prairies, DU's conservation efforts in the Boreal Forest, which are conducted in partnership with The Pew Charitable Trusts, focus on protecting wetlands and associated upland habitats. Because most of the region is publicly owned, DU works with federal, provincial, territorial, and First Nations governments to protect areas of great importance to waterfowl and other wetland wildlife. Additionally, DU works with corporations such as forestry and oil and gas companies to adopt “best management practices” that minimize impacts on wetlands and waterfowl in this natural resource−rich region.
The Future of Breeding Grounds Conservation
While it is always fascinating to observe firsthand how breeding ducks make the most of their few precious opportunities to pass on their genes, the information gathered by DU researchers on the breeding grounds is much more than a collection of interesting stories about individual birds. It is a living body of knowledge. For decades, researchers across North America have designed and conducted studies of breeding, migrating, and wintering waterfowl. They've compiled datasets that comprise hundreds and even thousands of records. Their analysis and interpretation of these data is the knowledge base that advances ecological science and guides DU's conservation delivery and public policy work across the continent. Science is the key to the continual improvement of our understanding of the complex social and ecological factors that drive habitat changes on the landscape, and therefore is essential to DU's ongoing success. In the future, we will continue to follow this proven, science-based approach to ensure that waterfowl will always have the habitats they need on the breeding grounds to thrive and fill the skies.
Dr. David Howerter is national director of conservation operations for DU Canada. Dr. Johann Walker is DU's director of conservation programs in North Dakota, South Dakota, and Montana.