Herbivorous geese are one of the most abundant wintering waterbird groups in East Dongting Lake wetland, in which the water levels and eco-hydrological environment have been greatly changed under the influence of various factors. 

Evaluating how the food conditions in East Dongting Lake wetland are affected by water regime changes and how the herbivorous geese respond to food resource changes could help offer scientific information on how to regulate hydrological regime in terms of wetland management and species conservation. 

Researchers from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences measured the variations in both food quantity and quality to explain the responses of the two herbivorous goose species (Lesser white-fronted goose Anser erythropus and Bean goose Anser fabalis) in terms of habitat selection and diet composition in two successive wintering periods of 2016/2017, which has early water level recession, and 2017/2018, which has late water level recession. 

By combining remote sensing, field survey, laboratory testing, and control experiment, the team found that sward height and dry biomass (indicating food quantity) and nitrogen and crude fiber content (indicating food quality) differed significantly between winters. 

As responses to the high-quantity/low-quality food during 2016/2017 wintering period, more geese switched to feeding on mudflat and exploited plants such as dicotyledons and moss. 

The tall swards of Carex spp. (dominant plants in the meadow) that developed during the first growing season decreased the food accessibility during the second growing season and hindered the exploitation of newly generated shoots by the geese. 

Nearly all the geese chose to feed on meadow, and Carex spp. made up the majority of their diet in 2017/2018 wintering period when there was more low-quantity/high-quality food. 

Compared with the globally vulnerable lesser white-fronted geese, the larger-sized Bean geese seemed to be less susceptible to winter food shortages and exhibited more stable responses. 

The food quality-quantity condition was the external factor influencing the geese responses, while morphological and physiological traits could be the internal factors causing different responses between the two species. 

The study entitled "Hydrology-driven responses of herbivorous geese in relation to changes in food quantity and quality" was published in Ecology and Evolution.