Water level affects availability of optimal feeding habitats for threatened migratory waterbirds |
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| Authors: | Yaara Aharon‐Rotman John McEvoy Zheng Zhaoju Hui Yu Xin Wang Yali Si Zhenggang Xu Zeng Yuan Wooseog Jeong Lei Cao Anthony D Fox |
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| Affiliation: | 1. State Key Laboratory of Urban and Regional Ecology, Research Center for Eco‐Environmental Sciences, Chinese Academy of Sciences, Beijing, China;2. Conservation Ecology Centre, National Zoological Park, Smithsonian Conservation Biology Institute, Front Royal, VA, USA;3. Key Laboratoryof Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing, China;4. Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, Beijing, China;5. Resource Ecology Group, Wageningen Universit, Wageningen, The Netherlands;6. Key Laboratory of Forestry Remote Sensing Based Big Data, Ecological Security for Hunan Province, Central South University of Forestry and Technology, Changsha, China;7. Animal and Plant Quarantine Agency, Korea;8. University of Chinese Academy of Sciences, Shijingshan District, Beijing, China;9. Department of Bioscience, Aarhus University, R?nde, Denmark |
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| Abstract: | Extensive ephemeral wetlands at Poyang Lake, created by dramatic seasonal changes in water level, constitute the main wintering site for migratory Anatidae in China. Reductions in wetland area during the last 15 years have led to proposals to build a Poyang Dam to retain high winter water levels within the lake. Changing the natural hydrological system will affect waterbirds dependent on water level changes for food availability and accessibility. We tracked two goose species with different feeding behaviors (greater white‐fronted geese Anser albifrons grazing species] and swan geese Anser cygnoides tuber‐feeding species]) during two winters with contrasting water levels (continuous recession in 2015; sustained high water in 2016, similar to those predicted post‐Poyang Dam), investigating the effects of water level change on their habitat selection based on vegetation and elevation. In 2015, white‐fronted geese extensively exploited sequentially created mudflats, feeding on short nutritious graminoid swards, while swan geese excavated substrates along the water edge for tubers. This critical dynamic ecotone successively exposes subaquatic food and supports early‐stage graminoid growth during water level recession. During sustained high water levels in 2016, both species selected mudflats, but also to a greater degree of habitats with longer established seasonal graminoid swards because access to tubers and new graminoid growth was restricted under high‐water conditions. Longer established graminoid swards offer less energetically profitable forage for both species. Substantial reduction in suitable habitat and confinement to less profitable forage by higher water levels is likely to reduce the ability of geese to accumulate sufficient fat stores for migration, with potential carryover effects on subsequent survival and reproduction. Our results suggest that high water levels in Poyang Lake should be retained during summer, but permitted to gradually recede, exposing new areas throughout winter to provide access for waterbirds from all feeding guilds. |
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| Keywords: |
Anser albifrons
Anser cygnoides
foraging ecology geese grassland habitat selection inundation Poyang Lake water table recession Yangtze River |
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