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Ecological Studies at the Woodworth Study Area

Woodworth Data and Planning for the Prairie Pothole Joint Venture

Ronald E. Reynolds1* and Michael A. Johnson2
1U.S. Fish and Wildlife Service, Habitat
and Population Evaluation Team, 1500 East Capitol Avenue,
Bismarck, ND 58501 and 2North Dakota
Game and Fish Department, 100 North Bismarck
Expressway, Bismarck, ND 58501

The North American Waterfowl Management Plan (1, NAWMP) was created in 1986 in response, primarily, to declining duck populations in North America. Under the NAWMP, focus areas, called Joint Ventures, were identified where management actions were considered critical to the long term welfare of waterfowl resources. The Prairie Pothole Joint Venture (PPJV), which includes the prairie pothole area of North Dakota, South Dakota, Montana, Minnesota, and Iowa, is considered a high priority joint venture of the NAWMP.

Between 1991 and 1994, a planning process was conducted in the PPJV area of North Dakota, South Dakota, and northeastern Montana to determine the type and amount of management treatment that would be necessary to meet the population objectives established for the Joint Venture (2). This planning process, called Multi-Agency Approach to Planning and Evaluation (MAAPE), involved participants from numerous government and non-government conservation organizations. The strategy was to bring appropriate information to bear on the fundamental components of the planning exercise. A major part of the exercise focused on biological information necessary to identify factors responsible for declining duck numbers and management treatments needed to reverse the decline.

From 1963 to present, the Woodworth Study Area (WSA) and surrounding area in southcentral North Dakota was a major focus area for waterfowl research and management trials conducted by the U.S. Fish and Wildlife Service (and recently the National Biological Service). Much of the information generated from these studies was used in the MAAPE process to answer questions and solve problems.

During the period 1966-81, over 3,300 duck nest records were accumulated at the WSA (3). These records and others gathered at WSA through 1984 were an important part of the nest records used by researchers to conclude that nest success in most of the U.S. Prairie Pothole Region was inadequate to maintain populations of upland nesting ducks and that predation was the most important cause of nest failure (4). This understanding was crucial to developing strategies that focused on treatments which reduced nest losses to predators.

Many of the treatments considered in the MAAPE process were designed to manipulate upland habitats in such a way that the cover was attractive to nesting hens and provided relative security from nest predators. A study conducted during 1974-76 at WSA defined a positive relationship between the height-density of grass cover and its attractiveness to nesting female ducks and their success (5). Numerous other subsequent studies have solidified these earlier findings and have led to treatments such as managed grazing, conversion of cropland to planted cover, and programs that idle perennial grass cover to increase the height-density of vegetative cover.

Increasing duck production in some landscapes requires intensive treatments. Studies at WSA have improved management's understanding of treatments such as nesting structures and small created islands (6, 7), which have become an integral part of the PPJV plan. In addition to influencing nest hatch rates of ducks, predators also prey on nesting hens. Understanding the magnitude of various mortality factors is imperative to developing proper management strategies for any wildlife population. Studies conducted, in part, in the WSA have demonstrated that predators such as red fox take a large number of nesting hens (8, 9), which accounts for a substantial portion of annual hen mortality. This information supports management initiatives that increase nest success because reduction in hen mortality can also be expected.

In summary, WSA has played a key role in advancing the understanding of waterfowl biology in the northern plains. It is beyond the scope of this paper to summarize all of the contributions of the station to waterfowl management. WSA has served as a laboratory for wetland and waterbird ecology and a headquarters for similar research in the surrounding land area. Numerous ideas about "how ducks operate" were conceived and tested at the station. Recently developed tools such as the Mallard Model (10) have synthesized data from duck studies at WSA and elsewhere in the Prairie Pothole Region so that managers can simulate the production potential of landscapes with various habitat configurations and make decisions about treatments. Such population models and advances in landscape assessment technology have resulted in a level of planning that far exceeds that available only a few years ago. The future value of this planning exercise will depend on efforts to continue collecting data to update and strengthen model weaknesses as landscape and wildlife components change.


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