Shifts in distribution of herbivorous geese relative to hydrological variation in East Dongting Lake wetland, China.

Studies on distribution dynamics of waterbirds and the relation with hydrological changes are essential components of ecological researches. East Dongting Lake is a Ramsar site and especially important wintering ground for herbivorous geese along the East Asian-Australasian Flyway. In this paper, based on annual (2008/09-2016/17) waterbird census data, we investigated the spatial-temporal distributions of three herbivorous goose species (Lesser White-fronted Goose Anser erythropus, Bean Goose Anser fabalis, and Greater White-fronted Goose Anser albifrons) within East Dongting Lake, and analyzed their distribution dynamics (denoted by percentage similarity index, PSI) relative to variations in hydrological regime. The results demonstrated that the distribution of the globally vulnerable Lesser White-fronted Geese changed obviously between years, whereas that of Bean Geese was more stable. Greater White-fronted Geese suffered drastic distribution variation during the study period. The PSI of Lesser White-fronted Geese was negatively correlated with between-year difference in water recession time and mean water level in October, whereas no obvious trend was found in Bean Geese. The Normalized Difference Vegetation Index (NDVI) was applied to detect changes in food resources of the geese, and significant correlations were also found between NDVI and hydrological factors. It was inferred that the variations in hydrological regime affected the annual distribution dynamics of Lesser White-fronted Geese by changing food conditions; whereas the effect on Bean Geese were not reflected in this study. Species traits may explain the differences in distribution dynamics among the three goose species. It was speculated that Lesser White-fronted Geese might be more sensitive to habitat change, whereas Bean Geese were more resilient. We suggested that regulating hydrological regime was crucial in management works. Our study could offer scientific information for species conservation in the context of habitat changes in East Dongting Lake wetland and provide potential insights into habitat management in this area.