|Conservation Planning in the Prairie Pothole Region
of the United States: Integration Between an Existing Waterfowl Plan and an Emerging
Non-game Bird Model
David N. Pashley1 and Rick Warhurst2
Comprehensive conservation plans designed to meet the ecoregional needs of an entire avifauna can be more efficient mechanisms for the achievement of conservation goals than the sums of plans for single species or species groups. Growing convergence between the North American Waterfowl Management Plan (NAWMP) and Partners in Flight (PIF) has created a fertile opportunity for conservation planning for all migratory birds. This paper describes progress in an example of this growing cooperative endeavor.
In the 1980s, biologists realized that populations of North American waterfowl had declined sharply in recent decades, primarily resulting from habitat loss and degradation. The 1986 NAWMP was designed to reverse these population declines through a partnership approach to restoring vital wetland and upland waterfowl habitat. The NAWMP established the goals of a continental breeding population of 62 million ducks and an average fall flight of 100 million ducks. To reach these goals, the NAWMP delineated 34 Waterfowl Habitat Areas of Major Concern in the United States and Canada. The seven most important of these, six in the U. S. and one in Canada, were identified as "Joint Ventures," each developing a unique set of conservation initiatives and partnerships. Joint Ventures are therefore the vehicles for implementation of the NAWMP.
The Prairie Pothole Joint Venture (PPJV) of the U. S. and the Prairie Habitat Joint Venture (PHJV) of Canada were identified as the top duck production areas of the continent. The PPJV includes more than 100,000 square miles in portions of Iowa, Minnesota, South Dakota, North Dakota, and Montana. The area was formerly dominated by tallgrass prairie in the east, mixed grass prairie in the west, and some shortgrass habitat, all interspersed with abundant wetlands. During the past century, conditions for wildlife in this area have deteriorated as wetlands have been drained and filled and grasslands plowed and planted for agricultural crop production. This drainage and conversion led not only to waterfowl population declines and to the creation of the Joint Venture, but also have reduced populations of non-game birds. In fact, grassland species may be exhibiting more rapid and widespread population declines than any other group of North American birds.
The PPJV Implementation Plan was developed to describe how the Joint Venture would achieve its first objective, to increase waterfowl populations through habitat conservation projects that improve natural diversity across the U. S. Prairie Pothole landscape. A second objective, to stabilize or increase populations of declining wetland/grassland-associated wildlife species in the Prairie Pothole Region, with special emphasis on non-waterfowl migratory birds, was added to the PPJV mandate in 1994.
The PPJV specified that its first objective would be accomplished through the conservation of habitat to support 6.8 million breeding ducks that achieve a recruitment rate of 0.6 by the year 2001 (recruitment rate is defined as young females fledged per adult female in the spring breeding population) under average environmental conditions. Numerous planning sessions were conducted to develop the strategies and plans required to accomplish this objective. In July 1991, many waterfowl biologists (researchers, population biologists, and habitat managers) met to develop guidelines for application of various habitat management treatments and strategies for the enhancement of duck production. These guidelines are necessary tools in developing the PPJV landscape management plans necessary for meeting the waterfowl population objectives.
Landscape management plans were formulated through a planning- and information-based management process called MAAPE (Multi-Agency Approach to Planning and Evaluation), using input from more than 250 resource managers, for 14 Waterfowl Management Districts (WMD) in North Dakota, South Dakota, and Montana. To summarize the MAAPE process, resource managers first determine the current population status of the species of concern (where are we?), and then set desired population goals (where do we want to be?). If the current population is lower than the population goal, then a cause for the deficiency is identified. Next, treatments or strategies are suggested for attaining the population goal (how do we get there?). Results of implementing the treatments are predicted through simulation models. The landscape is surveyed to locate treatment sites and, over the course of time, treatments are implemented. Finally, population monitoring and evaluation of treatments determine the effectiveness of the process for reaching the population goal (did we get there?).
Each MAAPE planning session began with a review of current information about the landscape, waterfowl breeding population, and recruitment rate. The Mallard (Anas platyrhynchos) was chosen as an indicator of conditions for other breeding ducks in the PPJV since it is the species for which the greatest amount of scientific information exists. Planners assumed that landscape management treatments that improve Mallard recruitment rates at least partially improve recruitment of the other ducks, particularly those that also nest in upland habitats.
Mean recruitment rate for Mallards across the 14 WMDs prior to 1985 was estimated to be 0.41, below the 0.49 recruitment rate necessary for population maintenance, and well below the PPJV objective of 0.6. Only two WMDs were producing Mallards above the level necessary to maintain populations. Therefore, much of the PPJV area, of key importance for Mallard production on the continent, was functioning as a Mallard population sink.
To raise recruitment rates, waterfowl habitat managers, population biologists, agriculture specialists, and other natural resource managers decided upon the array and magnitude of potentially beneficial management treatments and strategies that should be implemented in each WMD. Random, representative 4-square mile samples (335 sample plots in the 14 WMDs in Montana, North Dakota, and South Dakota) provided baseline landscape information. A population simulation model, the Mallard Productivity Model, was used to predict the effects of these management treatments on duck recruitment.
In the PPJV portions of North Dakota, South Dakota, and Montana, including approximately 4 million acres of Conservation Reserve Program (CRP) cover, Mallard recruitment rates have increased over the past decade to 0.54. Nine of the WMDs currently produce this species above maintenance population levels. The results of eventual full implementation of the landscape treatments prescribed in the 14 WMD management plans can be predicted through the Mallard Productivity Model. With CRP remaining in place and all habitat treatments implemented, the recruitment rate is expected to be 0.58, with all but one WMD exceeding maintenance level production. This is near the PPJV objective. Again, planners assume that if the Mallard recruitment rate is at this level, then other duck breeding populations will benefit as well. If, in addition, 91,000 culvert nest structures are installed in the region, the Mallard recruitment rate will increase to 0.63. Achieving this level of full implementation remains an expensive and daunting challenge.OTHER BIRDS
The growth of PIF has brought increased awareness and concern for bird populations other than waterfowl in the PPJV. Managers and planners have assumed that landscape management treatments designed to improve waterfowl production also provide benefits to many grassland and wetland non-game species. The extent of this overlap should be rigorously tested, and additional non-game bird conservation measures implemented, where waterfowl-directed efforts are insufficient.
As part of the PIF planning process, priorities, population objectives, and means of accomplishing objectives must be set for PPJV non-game birds. This process must be undertaken with considerably less data and understanding of natural history and demographics than were available for waterfowl. To address this issue, the PPJV Management Board established a Technical Committee with a non-game working group. The first task of this working group, development of a list of species of conservation concern, was accomplished in a workshop in early 1995 attended by many biologists and managers with knowledge of the status of these birds. The PIF prioritization process was a major source of information. Prioritization was supplemented by detailed analyses of population trends and by participants general understanding of conservation issues. Although the original language of the second objective of the Joint Venture stressed concern for declining species, participants felt that some species, although in decline, are still demonstrably secure, while others that have stable, increasing, or unknown population trends warrant close conservation concern owing to small populations and/or the importance of the prairies to the species as a whole. Those species included as conservation priorities, the reason for their inclusion, and the ecosystem within the Prairie Potholes most important to each, are listed in Table 1.
Table 1. Birds of the Prairie Pothole Region that warrant conservation attention
(PT - Population Trend: x - declining, x? - uncertain; AI - Area Importance; PS - small Population Size; TG - tallgrass, MG- mixed grass, SG - shortgrass; 3 = highest priority area; 2 = moderate priority; 1 = low priority; 0 = no priority)
For each of the three ecoregions (tallgrass, mixed grass, and shortgrass prairie), all priority species were divided into species suites that co-occur under certain habitat conditions and presumably respond to management practices in a similar manner. The habitat for each of these species suites thus becomes a target for conservation action (Table 2).
Table 2. Species Suites
1. Wetland suite 1 (Pied-billed Grebe, American Bittern, Virginia Rail, Sora, Wilson's Phalarope, Black Tern)
2. Wetland suite 2 (Yellow Rail, Sedge Wren)
3. Terrestrial suite 1 (Sedge Wren, Grasshopper Sparrow, Bobolink)
4. Terrestrial suite 2 (Loggerhead Shrike, Clay-colored Sparrow)
1. Non-vegetated wetland edges (Piping Plover, Least Tern)
2. Wet meadow (large tracts) (Yellow Rail, Nelson's Sharp-tailed Sparrow)
3. Semi-permanent large wetland with dense bulrush interspersion (Franklin's Gull)
4. Seasonal wetland zone (relatively large and deep) (Sora, Black Tern)
5. Seasonal wetland zone with upland grassy cover (Willet, Marbled Godwit, Wilson's Phalarope)
6. Seasonal/semi-permanent wetland with emergent cover (Pied-billed Grebe, Virginia Rail)
7. Semi-permanent/permanent wetland with emergent cover or seasonal wetland with dense upland cover (American Bittern)
8. Grasslands with a limited shrub component (Northern Harrier, Ferruginous Hawk, Short-eared Owl, Sprague's Pipit, Loggerhead Shrike, Baird's Sparrow, Grasshopper Sparrow)
9. Grasslands with a more extensive shrub component (Northern Harrier, Short-eared Owl, Loggerhead Shrike, Clay-colored Sparrow, Lark Bunting, Grasshopper Sparrow)
10. Grasslands near wetlands (eastern midgrass) (Northern Harrier, Short-eared Owl, Sedge Wren, LeConte's Sparrow, Bobolink)
11. Western, shorter, mixed grass grasslands (Ferruginous Hawk, Long-billed Curlew, Burrowing Owl, McCown's Longspur)
1. Relatively short grasslands (Ferruginous Hawk, Long-billed Curlew, Burrowing Owl, Lark Bunting, McCown's Longspur)
2. More mesic grasslands (Northern Harrier, Short-eared Owl, Sprague's Pipit, Loggerhead Shrike, Baird's Sparrow, and, if wetlands are present, Willet, Wilson's Phalarope)
One of the next steps in the planning process for non-game birds is to evaluate the impact of prevailing and potential management and land-use practices on these species suites. The PPJV Technical Committee under the leadership of the Northern Prairie Science Center has undertaken this process, which is yielding an array of conservation practices that can be used to benefit the priority birds.
Once species and habitat priorities are established through PIF planning and the impact of management practices are evaluated, some aspects of the MAAPE used for waterfowl planning may serve as useful models for the formulation of population and/or habitat objectives for non-game birds. Success of the MAAPE planning process is dependent upon accurate information. Much of the habitat information thus far compiled is applicable to all grassland birds. However, the level of knowledge regarding Mallard population size and recruitment is unlikely to ever be duplicated for high-priority non-game species. Nevertheless, the same expectations exist: 1) Risk of extirpation of sub-populations should be very small; 2) Recruitment rates should be sufficient to allow populations to persist or grow; and 3) Overall population size should exceed some designated threshold.
Population objectives and means of achieving them depend upon features of the landscape and how they are managed. These features are variable across the Northern Prairies. In the south and east, where row-crop agriculture predominates, objectives may be set in terms of protection of stationary blocks of habitat sufficient for high-priority species. Farther west, where entire districts retain relatively large percentage coverage by native or non-native grasslands, blocks may be less of an issue than maintenance of landscapes generally dominated by grasslands and wetlands. Much work remains in working through this step.
We thank Doug Johnson, Carol Lively, Ron Reynolds, and Jim Zohrer for helpful assistance in the preparation of this document.
2 Ducks Unlimited