A physiological assessment of wetland habitats for spring-migrating ducks in the agricultural landscapes of the southern Prairie Pothole Region

The conversion of grassland and wetland ecosystems in the Prairie Pothole Region (PPR) has been a pervasive challenge for conservationists dating back to the early 1900s. The legacy of ever-increasing agricultural intensity in the southern portions of the PPR, including eastern South Dakota, has left many wetland ecosystems in a matrix of intensive agricultural production. With little surrounding nesting cover, these wetlands are thought to have limited potential for waterfowl reproduction but may still play an important role facilitating migration of waterfowl en route to northern breeding areas during spring. My research sought to understand the contributions of wetlands in intensively-farmed landscapes for spring-migrating ducks. I measured a number of biotic attributes of wetlands including the density of aquatic invertebrates and submersed macrophytes and abundance of spring-migrating ducks. I also measured concentrations of lipid metabolites circulating in plasma of female lesser scaup (Aythya affinis) and blue-winged teal ( Anas discors) to understand refueling performance of migrants using wetlands with variable biotic and abiotic characteristics. Duck abundance, refueling performance, and prey abundance were generally similar across the upland cultivation gradient, if not slightly greater in more intensely-farmed landscapes. These results suggested wetlands in intensively-farmed landscapes in eastern South Dakota currently confer similar benefits to migrating waterfowl as those in less intensively-farmed landscapes. An analysis on wetland covariates and migrant refueling performance revealed density of fathead minnows ( Pimephales promelas) in wetlands was negatively associated with refueling performance. Further analyses suggested this finding was likely the result of trophic effects of fathead minnows on invertebrate and plant communities in the wetlands. Taken together, my results suggested wetlands in agricultural landscapes in eastern South Dakota can provide novel refueling habitats for migrating ducks when factors such as artificial connectivity or water permanency that facilitate fathead minnow colonization and persistence are controlled. Further, they raise questions about whether wetlands in intensively-farmed landscapes are indeed resilient to adjacent land use or simply compensate for degradation through increased productivity characteristic of landscapes with intensive crop production. Answering this latter question is key for understanding agricultural impacts and setting wetland restoration priorities in the region.