Ecological Distribution of Breeding Waterfowl Populations in North Dakota

Abstract

The distribution of breeding waterfowl populations on various wetland habitat types was investigated in Nori Dakota during 1967-69. Data were obtained by stratified random sampling techniques. The total wetland acreage in North Dakota was estimated to be about 3.2 million acres. Natural basin wetlands comprised about 77 percent of the acreage and 91 percent of the number of wetlands in the state and were utilized by about 76 percent of the state's breeding duck population. Among the four biotic regions of the state, numerical and areal composition of wetlands varied considerably. Natural basin wetlands varied from a low of about 4 percent of total wetland acreage in the Southwestern Slope Region to a high of 93 percent in the Prairie Pothole Region. About 84 percent of the statewide duck population occurred in the Prairie Pothole Region. Within the Prairie Pothole Region, seasonal (Class III) ponds comprised 36 and 23 percent, respectively, of the total acreage and number of wetlands, and semipermanent (Class IV) ponds and lakes comprised 18 and 3 percent, respectively, of these totals. Agriculture has had drastic effects on the wetlands in this region as evidenced by the fact that natural basin wetlands with tilled bottom soils (chiefly Class II and Class III wetlands) comprised about 29 percent of area but 52 percent of numbers of all wetlands. In the Prairie Pothole Region, seasonal ponds and semipermanent ponds and lakes were utilized by about 48 and 27 percent, respectively, of the total breeding ducks. Optimum environmental conditions for breeding dabbling ducks were present during years when large numbers and acreages of seasonal (Class III) pond basins contained surfacewlater. Semipermanent (Class IV) ponds and lakes were the principal habitats for breeding diving ducks, and were also important to dabbling ducks, particularly during dry years. J. WILDL. MANAGE. 37(1):39-50 The paramount importance of the glaciated prairie region as a breeding ground for North American waterfowl has been well established. This region contains innumerable shallow wetlands with discrete basins that are especially attractive to various species of dabbling and diving ducks during the nesting season. Unfortunately, the natural ecosystems within this region have been drastically altered by intensive agricultural development during the past 75 years. Since these environmental changes are continuing at an unabated rate, it is essential that their impact on the distribution, population densities, and ecology of breeding waterfowl should be monitored. The primary purpose of this report is to document the ecological distribution oif populaltions of breeding waterfowl on prairie wetlands in North Dakota from 1967 through 1969 so as to provide a basis for evaluating effects of future environmental changes. The data are based oln counts of breeding duck pairs on various types of wetland wzthin sample units that were selected by stratified random sampling techniques. The sample units were distributed within strata that were differentiated by biogeogralphical, physiographical, and ecological factors (Stewart and Kantrud 1972 ) . The habitats included are the major classes of natural basin wetlands (Stewart and Kantrud 1971), fluviatile wetlands, and various man-made wetlands. The permanence o\f surface water in five classes of natural basin wetlands varies in degree and is correlated with differences in the vegetation of the central zones of the wetlands. These classes, listed in order of increasing permanence, are: ephemeral ( Class I ) ponds, temporary ( Class II ) ponds, seaJ. Wildl. Manage. 37 ( 1 ) :1973