Back then the lake was choked with dense lotus vegetation in the warmer months. I certainly understand the negative effects of eutrophication, but it did seem that the aquatic vegetation increased the carrying capacity for waterfowl and waders. Just before the lake was treated with an aquatic herbicide, clearing the vegetation completely, we had sightings of White Ibis and Tri-colored Heron there. Of course chemical treatment did nothing to reduce the levels of nitrates and phosphates that caused the vegetation growth in the first place.
But, so much for Lake Springfield. Throughout my years of urban birding, one location has always hosted a healthy wintering population of ducks. Located in a 1950's era subdivision in east Springfield, the Southern Hills development features 3 small lakes. It is in these lakes that one can be sure to view Ring-necked Ducks, Lesser Scaup, Gadwall, and Mallards on any winter day.