An Assessment of Wood Duck Distribution, Abundance and Riparian Breeding Pair Habitats in South Dakota

Continental waterfowl populations have declined in recent years to all time low levels (Canadian Wildlife Service - U.S. Fish and Wildlife Service 1986). As with many states, South Dakota\u27s natural resource managers are working to reverse this trend. One duck species that has historically responded well to harvest and habitat management is the wood duck (Aix sponsa). Wood ducks were nearly exterminated in the early 1900\u27s as a result of unregulated harvest and habitat destruction. Since passage of the Federal Migratory Bird Treaty Act of 1918, ending spring shooting and market hunting, and a large-scale nest box erection program, the wood duck has shown its resilience and ability to respond to management (Bellrose 1990). Currently, continental wood duck populations are in good condition, but the loss of breeding and wintering habitat is still of much concern (CWS-USFWS 1986). Wood ducks occur in North America in three distinct populations: Atlantic, Pacific and Interior. Wood ducks in South Dakota occur in the western most portion of the area occupied by the Interior population. Past distributions of wood duck breeding pairs in South Dakota were primarily in the eastern one-half of the state (South Dakota Ornithologists\u27 Union 1991, Bellrose 1976). With development and maturation of cottonwood (Populus deltoides) dominated forests along riparian areas in western South Dakota, wood ducks are now inhabiting these once unoccupied areas (Ladd 1990). Numerous wood duck studies have been conducted in other regions of the U.S. (Fredrickson et al. 1990), but very few have been conducted in the northern Great Plains. For South Dakota, some information exists on wood duck brood habitats along portions of the Big Sioux River in Brookings and Moody counties (Smith 1982, Smith and Flake 1985) and the James River in Brown and Spink counties (Larson 1990), but sufficient breeding pair and habitat distribution information does not exist to adequately manage wood duck pairs and broods on a statewide basis. As a consequence, current distribution maps for wood ducks in South Dakota are inaccurate, and knowledge of breeding pair habitat quality is lacking. Wood duck breeding pair populations in South Dakota were estimated at 5,800 pairs in 1973 and 2,800 pairs in 1974, yet comprised only 0.6% of the states total estimated duck population (Brewster et al. 1976). They projected that most, possibly all, of the wood ducks in 1973 and 1974 occurred east of the Missouri River and 60% of these occurred along the James River. Schneider (1978) estimated the density of breeding wood duck pairs on the James River at 0.44 pairs/km in 1974 and 0.69 pairs/km in 1975. Larson (1990) reported similar estimates of 0.3 pairs/km in 1987 and 0.5 pairs/km in 1988 on the James River. The goal of this wood duck study was to gather baseline data on statewide breeding pair and habitat distributions along streams and rivers in South Dakota. My objectives were to (1) determine the distribution of wood duck breeding pairs in South Dakota, and compare current distribution with earlier distribution accounts; (2) qualitatively evaluate and rank South Dakota\u27s riverine habitats as to their suitability as wood duck breeding pair habitat; and (3) estimate wood duck breeding pair abundance on riverine areas ranked as excellent, good, fair or poor breeding pair habitat. To test for differences in wood duck pair abundance on South Dakota rivers and streams, between eastern and western South Dakota and among qualitative rankings, the following null hypothesis was developed. Ho : Wood duck pair abundance is similar between eastern and western South Dakota, and among excellent, good, fair and poor ranked sites