The effect of water level on the foraging behaviour of Bean geese

Abstract

In SATOYAMA environments that have been varied due to changes in the lifestyle of local people, the habitat of some species has also been altered. Therefore, to conserve the biodiversity of such environments, including Katano-kamoike pond where is managed as reservoir for rice cultivation and traditional hunting area, management plans that consider the ecology of target species are required. In the present study, I investigated the effect of water level on the foraging behavior of Bean geese Anser fabalis middendorffii at Katano-kamoike pond in Kaga City, central Japan; based on the results, I propose a water-level management plan. During the study periods, the water level at the site, which was measured with a standard water-level gauge, fluctuated between 20 and 65 cm. In general, the proportion of foraging Bean geese ranged from 0 and 1 when water depth was lower than 80 cm and those were low at higher water depth. In addition, the proportion of Bean geese foraging for the fruits of Water chestnuts Trapa natans decreased as the water level rose, while that of geese foraging for the rhizomes of emerging plants increased. These results were confirmed statistically using a generalized linear mixed model. Because the foraging behavior of Bean geese was affected by the water level at the study site, I suggest that it would be advisable to maintain a low water level in order to conserve the foraging grounds and the flexibility in the food selection of Bean geese.