Fall Food Habits of American Wigeon at Long Point, Lake Erie, Ontario

Abstract

We studied food habits of an abundant migrant, the American wigeon ( Anas americana), staging during the 1991 fall migration at Long Point, a World Biosphere Reserve and a Ramsar site on the north shore of Lake Erie. Food samples from 149 wigeons were analyzed; stems and leaves of aquatic plants (predominantly submerged macrophytes) comprised over 92% aggregate dry mass of the diet, seeds made up 7.8%, and animal matter 0.6%. A diverse array of plant species was identified; however, results indicate that wigeons were showing selectivity in plant species consumed. Stems and leaves of muskgrass ( Chara spp.), elodea ( Elodea canadensis) and bushy pondweeds ( Najas flexilus and N. guadalupensis) (aggregate percent dry mass 37%, 22%, and 18% for proventriculi, and 15%, 12%, and 38% for gizzards, respectively) comprised the bulk of the diet, although neither bushy pondweed nor elodea wholly dominated submerged macrophyte communities. Several submerged macrophytes, such as coontail ( Ceratophyllum demersum) and pondweeds ( Potamogeton spp.) which are common and widespread at Long Point and reported frequently as important in the diet of American wigeons elsewhere, were not found at all or only in trace amounts. Some sex, age, and seasonal differences in diet were detected; Chara spp. and tubers were eaten more frequently by adults than by immatures, Elodea canadensis was eaten in late fall by females but not by males, immatures ate Myriophyllum spicatum seeds more frequently than did adults, and Najas spp. was consumed more in late fall than in early fall.