Aharon-Rotman Yaara, McEvoy John, Zhaoju Zheng, Yu Hui, Wang Xin, Si Yali, Xu Zhenggang, Yuan Zeng, Jeong Wooseog, Cao Lei, Fox Anthony D
State Key Laboratory of Urban and Regional Ecology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing China.
Conservation Ecology Centre National Zoological Park Smithsonian Conservation Biology Institute Front Royal VA USA.
Ecol Evol. 2017 Nov 7;7(23):10440-10450. doi: 10.1002/ece3.3566. eCollection 2017 Dec.
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 [grazing species] and swan geese [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.
鄱阳湖大面积的季节性湿地由水位的剧烈季节性变化形成，是中国候鸟鸭科动物的主要越冬地。过去15年湿地面积的减少导致有人提议修建鄱阳湖大坝，以保持湖内冬季高水位。改变自然水文系统将影响依赖水位变化获取食物的水鸟。我们在两个水位不同的冬季（2015年持续水位下降；2016年持续高水位，类似于鄱阳湖大坝建成后预测的水位）追踪了两种具有不同觅食行为的鹅类（豆雁[食草类]和鸿雁[食块茎类]），基于植被和海拔研究水位变化对它们栖息地选择的影响。2015年，豆雁广泛利用相继形成的泥滩，以短而营养丰富的禾本科草甸为食，而鸿雁则在水边挖掘底物寻找块茎。这种关键的动态交错带在水位下降期间依次暴露水下食物并支持早期禾本科植物生长。在2016年持续高水位期间，两种鹅类都选择了泥滩，但也更多地选择了具有较长季节性禾本科草甸的栖息地，因为在高水位条件下获取块茎和新的禾本科植物生长受到限制。较长的禾本科草甸为这两种鹅类提供的能量收益较低的食物。适宜栖息地的大幅减少以及高水位导致它们只能选择收益较低的食物，可能会降低鹅类积累足够脂肪储备用于迁徙的能力，并对随后的生存和繁殖产生潜在的延续影响。我们的研究结果表明，鄱阳湖夏季应保持高水位，但允许其在冬季逐渐下降，露出新的区域，为所有觅食群体的水鸟提供觅食机会。
