In addition, many of these wetlands lay idle and are no longer grazed. This seems to allow cattails to replace native bulrushes. The emergent vegetation in many other wetlands was often harvested for livestock forage and bedding. Many of these wetlands also are now idle and dominated by cattails. The great increase in cattails has effects on many wildlife species in the prairie pothole region.
Ducks seem to avoid wetlands with monotypes of deep-marsh emergent hydrophytes like hybrid cattail.
Most studies of waterfowl I reviewed indicate that reductions in height and density of tall emergent plants generally increase use by breeding ducks. Whether these reductions are caused by fire, flooding, mowing, cultivation, insect damage, or grazing by muskrats or domestic livestock seems to make little difference. The increased use of semi-open prairie wetlands by ducks is probably from a combination of factors. These wetlands seem to have enough emergent cover to allow pairs to isolate themselves from conspecifics. These wetlands also usually contain open-water areas dominated by submerged aquatic plants that provide easily accessible supplies of insects, molluscs, and crustaceans that are known foods of adult female ducks and their young.