 A variety of factors can lead to increased levels of E. coli. A heavy presence of migratory waterfowl like geese is a common cause because their feces may run off into the water. Another is intense rainfall, which may stir sediment and pull debris from the shore. Townsend says the Corps has attempted mitigation efforts in the past, but they were less than effective. There have been past years where we did things to deter migrating birds. You know, a lot of people like to point the finger at Canadian geese. They're just one of the causes of this.