Preliminary observations of diurnal feeding patterns of Swan Geese Anser cygnoides using two different habitats at Shengjin Lake, Anhui Province, China

Abstract

Swan Geese Anser cygnoides wintering at two different areas of Shengjin Lake fed either by grubbing below ground rhizomes of Vallisneria asiatica or by grazing the above ground primary production of sedges Carex sp. and Canary Grass Phalaris arundinacea leaves. Activity budgets were compiled from geese using the two different foods and feeding behaviours showed little appreciable difference in time spent feeding (c. 50% of daylight hours) or resting (c. 30%), which were similar to previous observations from Poyang Lake of the species feeding on Vallisneria. In the absence of evidence of night feeding, the extended periods spent resting during the day suggests that the species is well able to meet its energetic needs at present foraging rates. However, to understand fully the profitability of the two habitats, detailed studies are required on the energetics of goose exploitation of Carex and Phalaris leaves and of Vallisneria rhizomes, including the effects of food depletion on the profitability of both habitats, and in relation to changes in body stores accumulated by the geese throughout the winter season. This is especially important if availability of these foods is likely to change at Shengjin Lake and at the many other lakes in the Yangtze River basin as a result of the hydrological effects of the Three Gorges Dam project, as these sites are the main winter strongholds for the global Swan Goose population.