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Conversion of natural wetlands to artificial wetlands is a global phenomenon that leads to loss of natural habitats for waterbirds, while these alternative wetlands may buffer the adverse effects of natural wetlands loss by providing waterbirds with suitable habitats. Yancheng National Nature Reserve (YNNR), a Ramsar wetland in China, is the largest wintering area for the globally endangered red-crowned crane (Grus japonensis). A remarkable part of natural wetlands within the YNNR has been reclaimed into aquaculture ponds in recent decades. In order to better understand the utilization of aquaculture pond by cranes and identify beneficial management actions, we investigated the wintering crane occurrence in ponds and quantified pond characteristics as mainly influence factors from November to March in 2017–2018 and 2018–2019. A total of 198 ponds were measured (91 in 2017–2018 and 107 in 2018–2019), out of which 42 ponds were found to be used by 48 groups of cranes (16 in 2017–2018 and 32 in 2018–2019). Family groups with 2–4 individuals of cranes were mostly encountered (91.7%) of all the group types. Wintering crane abundance in the aquaculture ponds was higher in 2018–2019 (105 individuals) than that in 2017–2018 (59 individuals). Five factors including water depth, species abundance, species richness, structures and distance to road were identified to influence use of ponds by cranes. However, crane occurrence was significantly associated with only water depth. This study recognized aquaculture ponds as a potential habitat for red-crowned crane. Efforts should be channeled into the sustainable development and maintenance of aquaculture ponds. More specifically, we recommended appropriate management practices to benefit wintering cranes by sequential harvesting of aquaculture ponds, maintaining aquaculture ponds in the buffer zone and keeping the water at a low level.

Spartina alterniflora has become the main invasive plant along the Chinese coast and now threatens the local ecological environment. Accurately monitoring the distribution of S. alterniflora is urgent and essential for developing cost-effective control strategies. In this study, we applied the One-Class Classification (OCC) methods of Maximum entropy (Maxent) and Biased Support Vector Machine (BSVM) based on Landsat time-series imagery to detect the species on the middle coast of Jiangsu in east China. We conducted four experimental setups (i.e., single-scene analysis, time-series analysis, Normalized Difference Vegetation Index (NDVI) time-series analysis and a compressed time-series analysis), using OCC methods to recognize the species. Then, we tested the performance of a compressed time-series model for S. alterniflora detection and evaluated the expansibility of this approach when it was applied to a larger region. Our principal findings are as follows: (1) Maxent and BSVM performed equally well, and Maxent appeared to have a more balanced performance over the summer months; (2) the Maxent model with the Default Parameter Set (Maxent-DPS) showed a slightly higher accuracy and more overfitting than Maxent with the Akaike Information Criterion corrected for small samples sizes (AICc)-selected parameter set model, but a t-test found no significant difference between these two settings; (3) April and December were deemed to be important periods for the detection of S. alterniflora; (4) a compressed time-series analysis model—including only three variables (December NDVI, March green and the third Principal Component in January, PC3)—yielded higher accuracy than single-scene analyses, which indicated that time-series analysis can better detect S. alterniflora than single-scene analyses; and (5) the Maxent model using the reconstructed optimal variables and 70 training samples over a larger region produced encouraging results with an overall accuracy of 90.88% and a Kappa of 0.78. The one-class classification method combined with a phenology-based detection strategy is therefore promising for the application of the long-term detection of S. alterniflora over extended areas.

The range pattern of wintering bird communities in the buffer zone of Yancheng Reserve, the largest coastal reserve, China, was investigated using 3S technologies. Differences in bird spatial distributions were also tested for spatial occupation, habitat type preference, and range overlapping ratio. The estimated average range sizes of the 16 bird species with enough sightings were 249.24 (28.17-435.25) km² of 95% fixed kernel (FK) and 131.03 (15.33-225.25) km² of minimum convex polygon (MCP). Phoenicurus auroreus and Lanius schach had the largest 95% FK and MCP range, respectively, whereas Larus ridibundus had the smallest 95% FK and MCP range. Most species utilized aquaculture and farmland areas largely, 85.97% of their core range included both habitats. The core range of any paired species overlapped 3.86-41.00 km², the average overlap ratio was 11.70% (0.58 - 21.91%). The geographic grids analyses showed that 1-3 species, 4-6 species and 7-9 species occupied 111 grids (64.9%), 47 grids (27.5%), and 13 grids (1.75%) individually, implicating low species spatial aggregation. This study suggested that differences in spatial distributions possibly contribute to the coexistence of sympatric species in Yancheng Reserve. [ABSTRACT FROM AUTHOR]

The function of the buffer zone of nature reserve is seldom evaluated in wildlife conservation. National Yancheng Rare Birds Nature Reserve is the largest coastal nature reserve in China. The environmental capacity of its core zone of 225.96 km² area is approaching saturation, and more and more birds have begun to utilize the buffer zone. We conducted a line transect survey in December 2010 to estimate bird density and evaluate the importance of the buffer zone. As a result, 34 protected species among the 4975 individuals were sighted, including 127 red-crowned cranes (Grus japonensis) and 868 common cranes (Grus grus). The overall density of protected species, winter migratory species, and resident birds was 1244.60 individuals/km², 396.88 individuals/km² and 758.94 individuals/km² respectively. The woodland, aquaculture, and farmland with >200 individuals/km² each signified the vital habitat of birds. Comparatively, density in the original habitat (woodland) is relatively higher than that in artificial habitats (aquaculture and farmland), which reached 81.0%, 13.9% higher than aquaculture and farmlands. These observations suggest that the northern buffer zone comprises of vital habitats for bird population. We recommend that priority should be given to the northern buffer zone to preserve the original habitat, whereas conversion of the original habitat to aquaculture and farmland use should be given great concern. [ABSTRACT FROM AUTHOR]

Exploring the effect of climate changes on population fluctuation of red-crowned crane is of great significance for the species protection and management. Here, based on the annual maximum population size of red-crowned crane wintering in Yancheng Nature Reserve (YNR) from 1981 to 2016, we tested the correlation between population size and the climate variables. The results showed that mean air temperature in wintering period showed a linear upward trend. Annual maximum wintering crane population was 623±33. Fitting the population size and the climate variables in the same year with GAMs indicated significant correlations between population size and mean maximum air temperature in November, mean minimum air temperature in December, mean air temperature in December, respectively. Time-lag effects were found between population fluctuation of red-crowned crane and the climate variables within 2, 4, 6 and 7 years earlier in December and February of the following year. Combination of the highest interpretations of the climate variables on population size included mean air temperature in January of the following year 6 years earlier, precipitation in January of the following year 7 years earlier and mean air temperature in December. Our results highlighted the importance of considering the effects of long-term climate variables on the population size of endangered birds, red-crowned crane. Then, an interpretation model with high deviance explained was explored. More and continuous attention should be paid to improve considerable measures of crane conservation based on climate change. [ABSTRACT FROM AUTHOR]

Buffer zone (BZ) of nature reserve is usually ignored in protecting bird diversity. Yancheng Rare Birds National Nature Reserve, the largest coastal reserve of China, supports higher bird diversity, but the buffer zone (BZ) function and its avian fauna composition remained unclear. In December 2010, we investigated the bird diversity in BZ of Yancheng reserve covering 188.8 km transect line. As a result, 50 species belonging to 26 families and 13 orders were identified. The general bird diversity index H in BZ is 2.291 with evenness of 0.583, and three orders viz., Ciconiiformes, Passeriformes and Charadriiformes, showed high bird diversity (H > 1). Considering high bird diversity and preference of 32 protected species including endangered red-crowned (Grus japonensis) and grey cranes (Grus grus), the northern BZ should be now considered to be priority protected area and even upgraded to core area. Although relationship index (I) between aquaticulture area and cultivated fields was 0.688, the dominant species compositon in aquaticulture area (five species comprised 75.3%) and cultivated fields (two species comprised 73.6%) was significantly different. Therefore both the habitats were equally important for bird conservation, and should be given the same protection efforts. Under the influence of natural forces and anthropogenic activities, the habitats are continuously changing. Therefore, we suggest monitoring the bird diversity annually, so that we can take targeted and effective protection measures. [ABSTRACT FROM AUTHOR]