Numerous studies have shown that large, herbivorous waterfowl can reduce quantity of aquatic plants during the breeding or
wintering season, but relatively few document herbivory effects at staging areas. This study was done to determine if feeding
activities of tundra swans (
Cygnus columbianus columbianus) and Canada geese (
Branta canadensis) had a measurable additive influence on the amount of aquatic plants, primarily muskgrass (
Chara vulgaris), wild celery (
Vallisneria americana), and sago pondweed (
Potamogeton pectinatus), removed during the fall migration period at Long Point, Lake Erie, Ontario. Exclosure experiments done in fall 1998 and
1999 showed that, as compared to ducks and abiotic factors, these two large herbivorous waterfowl did not have any additional
impact on above or below ground biomass of those aquatic plants. As expected, however, there were substantial seasonal reductions
in above-ground and below-ground biomass of aquatic plants in wetlands that were heavily used by all waterfowl. We suggest
that differences in large- and small-scale habitat use, feeding activity, and food preferences between tundra swans and other
smaller waterfowl as well as compensatory herbivory contributed to our main finding that large waterfowl did not increase
fall reductions of
Chara spp,
V. Americana, and
P. pectinatus biomass.
Keywords aquatic vegetation - Branta canadensis - Canada geese - Chara spp. - Cygnus columbianus - exclosure - herbivory - macrophytes - Potamogeton pectinatus - tundra swan - Vallisneria americana - waterfowl