Northern Prairie Wildlife Research Center
We defined wetlands as managed seasonal and permanent marshes on national wildlife refuges (NWR), state wildlife areas (SWA), and duck clubs (32,000 ha; Heitmeyer et al. 1989). We also included 125 ha of rice grown on 3 NWRs as wetlands (rice marsh), because these fields were left unharvested and available for foraging ducks during August and September (Miller 1987). In contrast, we defined rice fields as harvested commercial fields on private lands, which totaled 208,000 ha in 1980-81 and 223,000 ha in 1981-82 (Larson and Hettinger 1985). These fields could be dry (burned or unburned stubble), puddled by rain, intentionally flooded, and hunted or not.