Spring Habitat
The Neck of the Hourglass

Spring staging habitats are vital stopover areas for migrating ducks and geese. These wetlands also strongly influence the birds' reproductive success on their breeding grounds

By Steve Adair, Ph.D.

Next Services 1,000 Miles-For those of us who have traveled north during unpredictable spring weather, such warnings can be intimidating and force us to take stock of our fuel and supplies just in case things take a turn for the worse before reaching our next stop. Although these inhospitable stretches seem to get fewer and fewer as human populations continue to expand, the reverse is true for the millions of waterfowl that venture north every spring en route to their breeding grounds. As roads, farms, and buildings have expanded across the country to meet our needs, many of the wetlands critical to sustaining waterfowl on their journeys have been drained or severely damaged. The lower 48 states have lost more than 50 percent of their original wetlands and continue to lose more than 100,000 acres each year. In areas where waterfowl have historically concentrated in the spring, such as the Rainwater Basin of Nebraska, the Klamath Basin of California and Oregon, and the floodplains and marshes of the Upper Mississippi River Basin, the effects are even more dramatic, with more than 70 percent of the wetlands in these areas having been lost. The end result is millions of waterfowl crowding into a much smaller habitat base each spring, setting the stage for catastrophic disease outbreaks and increased competition for food resources.

While we need to maintain our focus on protecting and restoring grassland-wetland complexes on the breeding grounds, and ensure we retain current habitat resources on the wintering grounds, increased understanding and conservation of spring migration habitats is one of the last remaining frontiers in waterfowl biology. We need to enlarge the necks of these confining, migratory habitat hourglasses so that the streams of migrating waterfowl can pass through the habitats safely and quickly each spring.

The Role of Spring Habitats
Over the past 70 years we have learned a great deal about the behaviors, food and habitat preferences, survival, and population dynamics of waterfowl. Because waterfowl spend most of each year on breeding and wintering areas, much of what we know has come from research in these habitats. Migrational habitats, especially spring habitats, have not been well studied and, until recently, not considered especially critical.

As we learn more about the factors that drive waterfowl population levels (often referred to as vital rates), it has become increasingly clear that most of the important events occur on the breeding grounds. Rates of nest success, hen survival, and brood survival are especially critical in determining the annual population size of most species. Because spring migration is the last event before waterfowl initiate breeding, the outcome of this event may influence the success of their subsequent breeding efforts. Obviously, if spring habitat conditions are poor, causing waterfowl to crowd and succumb to diseases like avian cholera, hens that perish will not even have the chance to breed. Beyond this direct impact of poor spring habitat, more subtle changes might also have significant impacts.

Increasing evidence gathered on mallards, canvasbacks, and redheads by a number of scientists suggests that early-nesting hens within a species contribute more young to the fall flight each year than later-nesting hens. The reason is that ducklings that hatch early have a better chance of survival, not only during the summer, but also during the subsequent fall and winter. Therefore, it is reasonable to assume that abundant high-quality spring migration habitat may allow hens to replenish nutrient reserves, move on to breeding areas, initiate nests earlier, and achieve greater reproductive success than would have been possible with scarce, low-quality spring habitat.

This challenges us to think of spring migration habitat as pre-breeding habitat. Conservation efforts that encourage early nesting, such as preserving and restoring quality spring migration habitat, may help grow waterfowl populations.

Cornerstone Spring Habitats:
The Klamath Basin
Located along the Oregon-California border, the Klamath Basin historically contained about 185,000 acres of shallow wetlands. These wetlands were recharged by snowmelt each spring and provided migration habitat for up to 6 million waterfowl. In the early 1900s, the U.S. Bureau of Reclamation initiated projects to convert the wetlands in the Lower Klamath Basin to agricultural land, resulting in the loss of 75 percent of the original wetlands. To conserve the basin's remaining wetland habitat, six national wildlife refuges were established.

Although the number of waterfowl using the Klamath Basin has declined due to wetland drainage, an estimated 75 percent of Pacific Flyway waterfowl still rely on the resources there for their migrational stopovers. Recent satellite telemetry research conducted by Dr. Michael Miller and colleagues of the U.S. Geological Survey's (USGS) Western Ecological Research Center revealed that the majority of the marked pintails that wintered in California's Central Valley rested and refueled in the Klamath Basin before venturing to breeding grounds in the Prairie Pothole Region and Alaska, highlighting the basin's importance to this declining species.

Like wetlands throughout the Intermountain West, the Klamath Basin is threatened by increasing competition for limited water supplies. The water pie is divided among agricultural, wildlife, and fisheries interests. During the drought of 2001, federal officials, acting under mandates of the Endangered Species Act, diverted Klamath Basin water supplies into adjacent rivers to fulfill habitat requirements for several endangered fish. The result was very limited water available to the Klamath Basin's wetlands and agricultural irrigation systems. This crisis prompted DU to accelerate efforts with private landowners and the U.S. Fish and Wildlife Service to improve management, water quality, and water-use efficiencies of the remaining Klamath Basin wetlands.

Given the increasing demands on limited water supplies in the Intermountain West, precipitated by burgeoning human population growth, one of DU's greatest challenges in this region will be to ensure that enough water is allocated to wetlands when waterfowl need it the most. Our work in the Klamath Basin will be critical to establishing solutions that provide the best compromise for all the competing demands on this limited water resource. To give pintails and the numerous other waterfowl species that rely on the Klamath Basin each spring their best chance for survival and subsequent reproductive success, we need to ensure that abundant, quality habitat exists each spring.

The Rainwater Basin
and Platte River
South-central Nebraska contains one of the most vital yet threatened wetland complexes in North America: the Rainwater Basin/Platte River Ecosystem. Where more than 4,000 rainwater basins once dotted the landscape, fewer than 400 remain today. Due to upstream dams and extensive irrigation withdrawals, the Platte River has lost 70 percent of its historic flow, as well as 75 percent of the grasslands and wet meadows that once bordered the river. The 400 remnant basins and remaining river habitats are one of the lifelines that link millions of wintering waterfowl to their breeding grounds in the Prairie Pothole Region and the Arctic. Even now, in its degraded condition, 10 million snow geese, 900,000 white-fronted geese, 4 million mallards, 900,000 pintails, and millions of other ducks, geese, and sandhill cranes use these shallow wetlands during spring migration. When the basins are dry due to drought, these ducks and geese join the 450,000 sandhill cranes on the braided channels and sloughs of the nearby Platte River to find essential roosting and foraging habitat.

Without protection and restoration, the future of this vital waterfowl habitat is bleak. Ducks and geese are increasingly packed into the few remaining wetlands, resulting in periodic outbreaks of avian cholera. Previous cholera outbreaks have claimed the lives of hundreds of thousands of waterfowl in the Rainwater Basin. These losses, occurring as they do just prior to nesting, have significant repercussions for continental waterfowl populations. The best strategy to minimize these epidemics is to restore and protect wetland complexes to disperse waterfowl and reduce the concentrations that lead to stress and disease transmission.
Working with the Rainwater Basin Joint Venture, Nebraska Environmental Trust, Natural Resources Conservation Service, Nebraska Game and Parks Commission, U.S. Fish and Wildlife Service, and numerous private partners, DU has developed a vision to restore and protect four 3,000-acre wetland complexes strategically located across the basin to disperse spring populations. Last year, the first 1,000 acres were purchased, providing the springboard to acquiring 12,000 acres over the next 10 years. Recent research by Dr. Robert Cox and his colleagues at the USGS Northern Prairie Wildlife Research Center has found that pintails using the Rainwater Basin during spring migration prefer smaller wetlands with abundant annual plants such as smartweeds. Previous efforts in the Rainwater Basin have focused on protection of relatively large remnant wetlands that had persisted because they were difficult to drain. Most of the smaller wetlands have been lost, and by restoring the former diversity of wetlands contained in each of these 3,000-acre complexes, DU will increase both the quantity and the quality of the habitat base.

Central Kansas Wetlands
Located in central Kansas, the Cheyenne Bottoms State Game Area (SGA), Quivira National Wildlife Refuge (NWR), and McPherson Valley wetlands provide a critical wetland complex for migrating waterfowl. Both Cheyenne Bottoms SGA and Quivira NWR are also designated as Western Hemispheric Shorebird Reserve sites because of the exceptionally large numbers of shorebirds that use these areas during migration. Cheyenne Bottoms is also recognized as a Wetland of International Importance by international treaty, primarily due to the plethora of waterfowl that use the site during fall and spring migration. While the Cheyenne Bottoms and Quivira wetlands have been largely protected through public ownership, the McPherson Valley wetlands have undergone extensive drainage. In the early 1900s, a large drainage ditch, the Blaze Fork, was constructed. It reduced wetland acreage in the McPherson Valley from 9,000 to several hundred acres and the number of basins from 52 to 10.

In light of recent scientific evidence that early-nesting females provide a greater contribution to annual recruitment, DU initiated restoration and protection activities on the McPherson Valley wetlands to increase habitat resources available to waterfowl immediately prior to arrival on the breeding grounds. The Kansas Department of Wildlife and Parks, The Nature Conservancy, the U.S. Fish and Wildlife Service, the Natural Resources Conservation Service, and the R. Michael Rhoades Foundation have joined DU in these efforts. To date, the partnership has acquired or restored more than 2,000 acres of wetlands and adjacent uplands in the McPherson Valley, with an additional 1,500 acres targeted for restoration in the near future.

Once completed, restoration of these historic wetlands will contribute greatly to the number and diversity of wetlands available to waterfowl migrating through the mid-continent. Together with the nearby Cheyenne Bottoms and Quivira National Wildlife Refuge, the McPherson Valley wetlands will help reduce the bottleneck through which wintering waterfowl travel to their prairie breeding grounds.

The Upper Mississippi River
The Upper Mississippi River and its tributaries have a rich waterfowl history. Fall concentrations of migrating birds captured the attention of sportsmen and spawned many fabled hunting clubs and destinations near the river's headwaters in Minnesota and along the Illinois, Ohio, and Missouri rivers. The Upper Mississippi River and its nutrient-rich floodplain also became the focus of commerce and expanding agriculture, leading to the conversion of many of the wetlands into other land uses. With this conversion, migrating and wintering waterfowl populations declined, especially those species that could not easily switch to feeding on waste grain crops.
Of particular concern are scaup populations, which have been steadily declining since 1984. One hypothesis for this decline is that females arriving on the breeding grounds in poor condition must delay nesting until they can accumulate the nutrients necessary for egg laying and incubation. Delayed nesting may lead to lower nest success and lower brood survival. To begin to examine this hypothesis, Michael Anteau and Dr. Alan Afton of the U.S. Geological Survey's Cooperative Fish and Wildlife Research Unit at Louisiana State University compared the body condition of lesser scaup along the Mississippi Flyway from Louisiana to Manitoba to scaup body condition determined from previous studies. Preliminary results show that body mass of females was significantly lower in Minnesota and Manitoba in the spring of 2000 and 2001 compared to the same locations in the 1980s. The body mass of female scaup did not differ in Louisiana and Illinois between these time periods, suggesting greater concern for habitat conditions in the upper river basin. Additional work by Anteau and Afton has shown a decline in amphipods, also called scuds or freshwater shrimp, in the diets of spring migrating scaup in these areas, which could be related to the reduction in body mass. Reduced water quality, changes in plant communities, and the introduction of minnows could all be contributing to declining amphipod populations.

The multiple impacts of the large-scale land conversion that has occurred in the Upper Mississippi River and its tributaries on waterfowl and other wildlife, fisheries, and water quality have lead to new partnerships among conservation groups sharing a common goal of restoring the natural resources of the river and its watershed. DU has joined forces with the Natural Resources Conservation Service, the U.S. Fish and Wildlife Service, Minnesota Department of Natural Resources, the Legislative Commission on Minnesota Resources, Illinois Department of Natural Resources, Wisconsin Department of Natural Resources, Iowa Department of Natural Resources, the McKnight Foundation, and many others to restore and enhance wetlands in the Upper Mississippi River Basin. These efforts include restoring previously drained wetlands, establishing buffers around existing wetlands to reduce sedimentation and nutrient loading, and installing fish barriers to prevent rough fish from degrading water quality and reducing the wetland plant food base. Through these partnerships, we can provide improved habitat with abundant, preferred foods for migrating scaup and other waterfowl species, while also helping to reduce regional water-quality problems. The former may be an important piece of the puzzle for reversing the long-term decline of continental scaup populations.

Ongoing research will test our assumptions of the role these spring staging area habitats play in setting the stage for successful breeding. During this past winter, female pintails were marked with radio transmitters in Texas by Dr. Robert Cox and his colleagues. These birds will be followed as they move from Texas through the Rainwater Basin and Platte River in Nebraska, and then on to their prairie breeding grounds. Data from this study will help us understand more fully the preferred spring habitats, as well as establish baseline information on how long pintails spend in these habitats, so that we can see how this varies over time with changes in habitat quality and quantity. These data will help us fine-tune the focus and magnitude of our conservation efforts on spring migration habitats.