Abstract
The ideal habitat use of waterbirds can be considered to be fixed, but current habitat use depends on environmental conditions, especially those of food characteristics, considered crucial to their use of habitats. Understanding how waterbirds respond to variation in food availability at degraded wetland sites and change their habitat use patterns over spatial and temporal scales should direct future conservation planning. The objectives of this study were to identify these spatial-temporal foraging habitat use patterns of Hooded Cranes (Grus monacha) and their relationship with food characteristics in the severely degraded wetlands of the Shengjin and Caizi lakes along with the Yangtze River floodplain. We investigated the changes in food characteristics, relative abundance and density of Hooded Cranes in various habitat types across three winter periods from November 2012 to April 2013. We examined the effect of these winter periods and habitat types on the pattern of use by the cranes and explored the relationship between these patterns and food characteristics using linear regression. The food characteristics and habitat use clearly changed over spatial-temporal scales. In the early and mid-winter periods, the most abundant, accessible and frequented food resources were found in paddy fields, while in the late period the more abundant food were available in meadows, which then replaced the paddy fields. There were fewer effects of winter periods, habitat types and their interactions on habitat use patterns except for the effect of habitat types on the relative abundance, determined as a function of food abundance, but independent of food depth and sediment permeability. In response to the degradation and loss of lake wetlands, the cranes shifted their habitat use patterns by making tradeoffs between food abundance and accessibility over spatial-temporal scales that facilitated their survival in the mosaic of these lake wetlands.
Highlights
The ideal habitat use of waterbirds can be considered to be fixed, but current habitat use depends on environmental conditions, especially those of food characteristics, considered crucial to their use of habitats
Food characteristics and foraging areas The food characteristics and foraging areas were erratic on the grounds within the Shengjin and Caizi lakes across winter periods (Table 1)
Our results indicated the Hooded Cranes have been quite flexible strategies in changing their foraging habitat use patterns over time and space in order to improve their fitness on their dwindling food resources
Summary
The ideal habitat use of waterbirds can be considered to be fixed, but current habitat use depends on environmental conditions, especially those of food characteristics, considered crucial to their use of habitats. Understanding how waterbirds respond to variation in food availability at degraded wetland sites and change their habitat use patterns over spatial and temporal scales should direct future conservation planning. The waterbirds would be faced with complex decisions about how to make use of patches over spatial and temporal scales Their flexibility in habitat use patterns is critical in coping with a changing ecosystem (Quaintenne et al 2010; Amano 2012). In some highly dynamic ecosystems, such as river-lake wetland networks, the capacity for assessment and use of high-quality food items may be the essential adaptation once the optimal habitats are located, but there is less direct evidence that waterbirds have the capacity to adjust spatial behavior in real time in order to adapt to changing environments (Weimerskirch et al 2003)
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