Prairie potholes were formed by [?]. The prairie potholes produce so many ducks that this northern prairie region is often called the North American [?] and produces up to percent of all waterfowl produced in a given year. The ecology of the Prairie Pothole Region is defined by cycles of rain and [?]. Due to the loss of prairie potholes there has been an increase in peak flows and effective discharge in prairie streams leading to in-stream and stream bank .