The importance of Zizania latifolia as food for Geese and Swans at inland waters and differences in foraging methods among species

Abstract

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.

Effects of grazing on underground parts of marsh plants by wintering Middendorf's bean goose Anser fabalis middendorffii: Its role as a keystone species in plant communities

“…Rhizomes and roots of Zizania species are important foods for waterfowls at stopover and wintering sites (Giroux & Bedard, 1987;A. Watanabe, 2012;A. Watanabe et al, 2008;Zacheis et al, 2001).…”

“…These results indicate that the intensity of interspecific competition is restrained by the grazing behavior of A. fabalis middendorffii . Rhizomes and roots of Zizania species are important foods for waterfowls at stopover and wintering sites (Giroux & Bedard, 1987; A. Watanabe, 2012; A. Watanabe et al, 2008; Zacheis et al, 2001). Grazing pressure results in efficient supplementation of foods for A. fabalis middendorffii in the Katano‐kamoike pond.…”

“…However, A. fabalis middendorffii forages not only on farmlands, but also on wetland plants in lakes and ponds that are used as resting sites (A. Watanabe et al, 2008;Zaoh et al, 2010). In particular, A. fabalis middendorffii frequently forages on fruits, rhizomes, tubers, and roots of aquatic plants both underwater and underground.…”

Decrease in population of swans (Cygnus spp.) due to the development of areas adjacent to the wintering site

“…The wetland protected area at the mouth of Nakdonggang was not set up with a buffer zone; therefore, the urbanized area expanded rapidly near the wintering site of Cygnus spp. Moreover, the sharp decline in farmland, including paddy elds (Shimada, 2014, Watanabe et al, 2008, which are used as major feeding and resting areas by Cygnus spp., was notable. It failed to prevent a sharp decline in the rice paddies, which provides food for the Cygnus spp., and showed why the characteristics of wintering population changes in the two species were different.…”

“…In general, Cygnus spp. in Northeast Asia mainly uses rice paddies as feeding and sleeping grounds in winter (Shimada, 2007;Watanabe et al, 2008;Fujioka et al, 2010); they can be considered to have adapted to agricultural activities, owing to the relative ease of obtaining food. Despite this being the main wintering site, the populations do not spend the entire wintering period in one place.…”