Northern Prairie Wildlife Research Center
| East Rivera | West Rivera | ||||
| Dens | Populationb | Dens | Populationb | ||
| Identified ducks at dens (N) | 1452 | 113 | |||
| Species composition (%) | |||||
| Mallard | 20.3 | 17.0 | 67.3 | 40.4 | |
| Northern pintail | 23.1 | 19.7 | 20.4 | 10.1 | |
| Northern shoveler | 10.7 | 9.7 | 1.8 | 7.8 | |
| Blue-winged teal | 31.8 | 33.8 | 4.4 | 19.0 | |
| Gadwall | 9.2 | 15.6 | 2.7 | 8.8 | |
| American wigeon | 1.9 | 1.8 | 0 | 10.5 | |
| Green-winged teal | 3.0 | 2.3 | 3.5 | 3.5 | |