Date of this Version
The Prairie Naturalist 41(1/2): March/June 2009, pp 1-27
Many wetlands in the northern Great Plains west of the Missouri River are stock ponds, created by impoundment of natural drainages or excavation of existing wetlands to provide water for livestock or improve habitat for waterfowl. We evaluated factors influencing use of wetlands by breeding duck pairs and broods relative to modification, water regime, size, and hydrological location on United States Forest Service lands within the Grand River National Grassland in northern South Dakota (2003 and 2004). Responses for both indicated pairs and broods were related positively to wet area, total wetland area within 4 km, emergent edge cover, and shoreline development index, and related negatively to basin cover (proportion of basin area with emergent cover). Duck responses were higher for instream than for isolated wetlands. Wetland type (water regime and modification) was a critical factor related to number of indicated pairs and probability of mallard (Anas platyrhyncos) use in late May. The negative response of indicated pairs to basin cover in May is associated with the high use of modified semipermanent wetlands, where wetland morphology and water depths limit emergent cover to the perimeter. Emergent edge cover was a critical factor for indicated pairs in May and for probability of use by broods in early July. The influence of wetland size and proximity to other wetlands was evident in five of eight models for pairs and all three brood models. The complexity of and variability among our models demonstrated the seasonal complexities of wetland conditions and waterfowl life history and habitat needs.