Abstract
From November 1997 to February 1998, the diet of geese and swans was investigated at 12 lakes in Japan. Middendorff's Bean Goose Anser fabalis middendorffii, Whooper Swan Cygnus cygnus and Bewick's Swan C. columbianus were all frequently observed to forage on aquatic vegetation at the surface of inland waters. The rhizomes of Zizania latifolia occupied more than 50% of diets of all three species. Phragmites australis, Typha angustifolia and submerged plants were rarely foraged on by geese or swans, suggesting that these are not important foods for them. This study also showed that Middendorff's Bean Goose and Whooper Swan frequently used inland water surfaces as foraging sites whereas Greater White-fronted Goose A. albifrons did not. Utilization of inland water surfaces as a foraging site by Bewick's Swan was observed only in a limited region. Whooper Swan mainly foraged on the rhizomes of Z. latifolia under water whereas Bewick's Swans mainly exploited Z. latifolia on shore.
