Use of Sago Pondweed by Waterfowl on the Delta Marsh, Manitoba

Abstract

Periodic sampling of sago pondweed (Potamogeton pectinatus) in exclosures and plots open to waterfowl activity on the Delta Marsh, Manitoba [Canada], indicated an average utilization of 60.5 g/m2 (40.4% of standing crop) foliage and 26.3 g/m2 (42.9%) tubers between July 1973-June 1974. Intensity of use varied greatly among plots. Mallards (Anas platyrhynchos), canvasbacks (Aythya valisineria) and coots (Fulica americana) were the most commonly observed species on the study plots. A surplus of submerged aquatic plant food evidently existed on the Delta Marsh at observed waterfowl population levels. Heavy utilization of certain plots in 1973 resulted in a relative decrease (open vs. control plots) in the 1974 midusmmer standing crops of those stands. It seems likely that heavy use of a single stand over several consecutive seasons might result in decreased plant production. Selection of more productive sites by feeding waterfowl would eliminate such an effect.