Trumpeter swans are herbivores that can graze on aquatic plants to a depth about 1 m.  Although the eating habits of swans have the potential of altering the macrophyte community (both qualitatively and quantitatively), few studies have been conducted to examine these effects.  Each year more than 230 trumpeter swans congregate on several of the 21 managed pools in Seney National Wildlife Refuge.  This population has increased 15% each year since 1991.  In June 2006, ten fences were constructed around a 5m x 5m plots (5 in a swan-dense pool and 5 in a swan-free pool) to exclude swans and other waterfowl.  A plot that was exposed to waterfowl grazing was also located adjacent to each fenced plot.   After 8 weeks each plot was sampled for plant species and densities (determined by dry weight).  No significant difference was detected between grazed and non-grazed plots although the average mass of plants normally grazed by waterfowl (Potamogeton sp., Sagittaria sp., and Vallisneria americana) was reduced in plots exposed to grazing from both swan and non-swan pools.  The patchy distribution of macrophytes in this preliminary study may have decreased the power of our statistical analysis.  Future experimental designs are discussed.