Rex R. Johnson

A LANDSCAPE APPROACH TO CONSERVING WETLAND BIRD HABITAT IN THE PRAIRIE POTHOLE REGION OF EASTERN SOUTH DAKOTA

Resource managers confronted with preserving ecosystems for prairie wetland birds in fragmented landscapes require landscape studies that direct conservation efforts over broad geographic regions. We investigated the role of local and landscape factors affecting habitat suitability by integrating remotely sensed wetland and land-cover data with wetland bird habitat models. We linked habitat models with locations of easement and fee-title wetlands to evaluate spatial location and extent of protected, suitable habitat. We also simulated impacts of the loss of small wetlands on suitability of larger wetlands for mobile species that use multiple wetlands. Lastly, we evaluated the efficacy of waterfowl habitat programs in preserving suitable habitat for nongame wetland bird species to recommend strategies for maximizing regional landscape connectivity. Regional databases constructed for this study indicate that easement and fee-title tracts encompass 13.9% (1.2 million ha) of land area and protect 19.8% of the wetlands in eastern South Dakota, USA Proportion of protected wetlands is highest for semi-permanent (32.3%), intermediate for seasonal (25.6%), and lowest for temporary wetlands (15.8%). A stratified, two-stage cluster sample was used to randomly select 834 semi-permanent and seasonal wetlands that were surveyed for birds in 1995 and 1996. Logistic analyses indicate that habitat suitability for some species (e.g., Virginia rail, pied-billed grebe) is related to local vegetation conditions within wetlands, while suitability for others (e.g., northern pintail, black tern) is related to landscape structure at larger scales. As a result, unfragmented prairie wetland landscapes (i.e., areas with wetland complexes embedded within upland grasslands) provide habitat for more species than isolated wetlands in tillage fields. Models developed from survey wetlands were used to classify habitat suitability for all semi-permanent and seasonal wetlands in eastern South Dakota. Small wetlands are critical components of the surrounding landscape that influence habitat suitability of larger wetlands. Models used to reclassify suitability of larger remaining wetlands after small wetlands (<0.5 ha) were removed indicate that species most vulnerable to loss of small wetlands are vagile species that exploit resources over broad spatial scales. Number of wetlands suitable for northern pintails, a mobile species that uses multiple wetlands within a season, decreased 20.7% when wetlands <0.5 ha were removed. Historic paradigms dictating waterfowl habitat protection efforts also have conserved habitat for nongame bird species. Modern paradigms that acknowledge the importance of small shallow wetlands to breeding waterfowl have shifted the focus of protection towards preserving habitat for species that occupy more abundant seasonal wetlands. Cessation of protection efforts would result in further fragmentation of regional wetland landscapes. We recommend that wetlands be acquired not only to consolidate suitable habitat within protected core areas but also to ensure that core areas coalesce to preserve connectivity among regional wetland landscapes.

LOCAL AND LANDSCAPE-LEVEL FACTORS INFLUENCING BLACK TERN HABITAT SUITABILITY

Wetlands throughout eastern South Dakota were surveyed (1995-97) for foraging and nesting black terns (Chlidonias niger) to evaluate local and landscape factors influencing habitat suitability We surveyed 834 randomly selected, semipermanent, and seasonal wetlands that were stratified by physiographic domain, wet- land density, and wetland surface area. A discriminant function model was used in a geographic information system (GIS) to classify habitat suitability of all semipermanent wetlands in eastern South Dakota. We calcu- lated number of suitable, protected wetlands by combining wetlands with easement and fee-title tracts in the GIS. Black terns nested in 7.8% and foraged in an additional 17.9% of semipermanent wetlands. Significant variables in the discriminant function were wetland area, total semipermanent wetland area within the wetland complex, and grassland area in the upland matrix. Black terns were an area-dependent species that occupied large (f = 18.9 ha) wetlands located within high-density wetland complexes. Black terns typically occurred in wetlands within landscapes where <50% of upland grasslands were tilled. Classification rates were high (76- 100%), indicating that the model identified unsuitable wetlands using wetland area and landscape-level attri- butes. Characteristics of entire landscapes must be considered in habitat assessments because wetlands that do not correspond to landscape-scale habitat requirements may not be suitable despite favorable local condi- tions. Lower correct classification rates (22-78%) for occupied ponds indicated that suitability also is dependent on local conditions for wetlands which correspond to habitat requirements from a landscape perspective. Suitable black tern nest sites occurred within regenerating or degenerating wetlands where vegetation structure rather than species of vegetation dictated suitability of nest substrates. Wetland acquisition programs have protected 44% of wetlands suitable for black terns. Future wetland acquisitions should maintain the integrity of entire prairie landscapes in additional to attributes of individual wetlands.

Temporal distribution of waterfowl in eastern South Dakota: Implications for aerial surveys

The U.S. Fish and Wildlife Service and Canadian Wildlife Service incorporate information from annual aerial and ground counts of waterfowl into harvest management strategies. Timing of population surveys is thought to be optimal for early nesting species but may not reliably reflect the status of species with later migration chronology. The purpose of this study was to evaluate effects of survey timing on diving duck and duck brood abundance indices in eastern South Dakota. Findings indicate that timing of aerial breeding surveys occurred too early in eastern South Dakota to accurately reflect diving duck population status because birds had not yet settled into breeding habitats and aerial production surveys did not coincide with peak duck brood abundance. Diving duck abundance from aerial surveys conducted during 10–17 May were higher than indices from ground surveys conducted 2 weeks later because lesser scaup (Aythya affinis), ring-necked duck (Aythya collaris), and bufflehead (Bucephala albeola) were still migrating through eastern South Dakota. Ground-survey estimates of redhead (Aythya americana) and canvasback (Aythya valisineria) abundance exceeded the upper limit of 95% confidence intervals for aerial survey estimates. Results from our second year of study showed an 11-fold decrease in lesser scaup abundance and an 8-fold decrease in ring-necked duck abundance in the two weeks following aerial breeding surveys. Brood abundance of dabbling and diving ducks peaked 1–1.5 months after aerial production surveys conducted in early July. Late-nesting indices calculated from aerial surveys were unrelated (P=0.21) to number of late-hatching broods, whereas number of broods hatching after aerial surveys was correlated with late-nesting indices from ground surveys (r2=0.74, P<0.01) and with number of July ponds (r2=0.77, P<0.01). We encourage scientists to initiate a more thorough evaluation of survey biases to ensure that trends accurately reflect status of duck populations and to explore the possibility of using a separate late May/early June aerial survey after diving ducks have settled into habitat as a way of assessing breeding population trends for these species.

Landscape-Level Planning for Conservation of Wetland Birds in the U.S. Prairie Pothole Region

There are many ongoing, extensive, and well-defined wildlife conservation issues in the Prairie Pothole Region (PPR) of North America. Substantial programs have been developed to address these conservation issues in the United States portion of the PPR. Loss and degradation of wetland and upland habitats are the primary conservation issues affecting wetland birds in the PPR. Identification of priority conservation areas within the PPR is important given limited conservation funds and the large area, diversity of landcover, and variation in bird distribution and density within the region. Land use and conservation issues vary across the PPR. Some physiographic regions such as the Agassiz Lake Plain along the Minnesota/North Dakota border are heavily cultivated and have virtually no wetlands or grasslands remaining. Landscapes such as these require extensive habitat restoration, although high land prices and competing land uses limit what can be accomplished. Other parts of the PPR have considerable areas of intact wetlands and/or grasslands that are used for cattle ranching or operations that include both cattle and crop agriculture. These landscapes are more conducive to conservation of existing habitat, which is invariably cheaper than habitat restoration; however, some conservation programs have funding dedicated to habitat restoration. Therefore, all landscapes and treatments are considered when planning for conservation action.

An Emerging Agency-Based Approach to Conserving Populations Through Strategic Habitat Conservation

This chapter describes a framework for strategic habitat conservation (SHC) that enables the efficient maintenance of wildlife populations at objective levels through protection of existing habitat, habitat restoration, and habitat manipulation. The SHC approach is planning intense; requires the integration of planning, conservation delivery, monitoring and research; and benefits from inter-agency collaboration and coordination. The technical elements of SHC are biological planning, conservation design, assumption-driven research, and mission-based monitoring. Biological planning, conservation design, and research and monitoring blend together in an iterative process. However, the process achieves its full value only when all five elements, including conservation delivery are in place. Biological planning is the systematic application of scientific knowledge about species and habitat conservation. It includes articulating measurable population objectives for selected species, considering what may be limiting populations to less than objective levels, and compiling models that describe how populations are expected to respond to specific habitat conservation actions. Conservation Design is predicated on the belief that the potential to affect populations varies in space in response to site characteristics and landscape context. The development of maps predicting patterns in the ecosystem is a significant feature of Conservation Design.