The Effect Of Lake Wetland Degradation On Foraging Activities Of The Wintering Hooded Crane (Grus Monacha)

The Hooded Crane is a large migrating wader, which forage in group. As an indicator species of wetland environment, they are sensitive to wetland changes. They are migrate to in the wetlands of the middle and lower Yangtze River floodplain in annual winter. The Shengjin Lake and Caizi Lake are important wintering sites along the Yangtze river in Anhui province. Recent years the foraging habitat of wintering Hooded crane is degenerating and crushing because of human interference, especially the high density of cage aquaculture and livestock. It is very significant to study the mechanism of wintering Hooded crane suitable habitat degradation and the response of species in degradation of habitat for future wintering population protection plan and implement the protection activities.We investigated the habitat utilization and flock pattern of wintering Hooded cranes in Shengjin Lake and Caizi Lake in the winter period from 2013 to 2014. The flock size and age structure were observed by scan sampling. Food abundance and the intensity of human disturbance were collected by sampling method. The population quantity, flock characteristics, distribution pattern and foraging preference of wintering Hooded cranes were analyzed, and the relationship between food resources, disturbances and flock size were illustrated using the generalized linear model. With the remote sensing image interpretation and vegetation normalized analysing from 1984 to 2014, we quantified the status quo of lake habitat degradation, compared the history and present of suitable habitat distribution of Hooded cranes along the Yangtze river in Anhui Province, and explored the ecological response of wintering Hooded cranes foraging activities on lake wetland degradation and loss.According to the evaluation of foraging habitat quality of wintering Hooded cranes, we found that the most suitable and unsuitable habitat area were both declined, and less suitable habitat area increased significantly. At present, with the shrinking of the most suitable habitat along the Yangtze river in Anhui, the Hooded cranes mainly distributed in sub-suitable habitat for foraging. The Hooded cranes positively changed the foraging distribution and flock pattern in the degradation of habitat for the largest forage benefits and minimum risk of predation by adjusting the foraging strategy.Foraging habitat quality influences the distribution pattern, and the Hooded cranes foraging distribution has transferred from mudflats to meadows and paddy fields along the Yangtze river in Anhui Province. Recently, the Hooded cranes concentratedly distributed on the paddy fields and meadows in the upper area of Shengjin Lake, and some on the traditional foraging habitat of mudflats. Tongxin, Xinsheng, Bailian, Shegan and Yang’etou were the main foraging sites, and Dazhou, Xinjun, Chi’an were temporary foraging sites. In these areas, the hooded cranes have no obvious predators, while the major predation risk comes from human disturbances. The foraging distribution and flock pattern of hooded cranes were different obviously in three habitats during wintering periods. In Caizi lake, the foraging activities space of wintering Hooded cranes reduced seriously. The cranes mainly distributed in Meihua to Shuangxing and Bajiao of Caizi Lake, the paddy field of Meihua and its near the ponds were mainly the foraging habitats of Hooded cranes, while the meadows and mudflats of aquatic breeding ponds were temporary feeding grounds.The flock of foraging distribution of Hooded cranes were distinguished the flock of family cranes from group cranes in over-wintering stages. The foraging flock distribution, flock size and age composition were significantly different in different periods. In the early and middle wintering periods, the Hooded cranes of Shengjin Lake took paddy fields as their major foraging habitat, where the foraging individuals and flocks were the highest. In the late period, the cranes took meadows as a major foraging habitat. Flock size varied significantly among different habitats (F2,273= 5.797, P=0.003), while the age composition of foraging flock were not distinct changed (F2,273=0.836, P=0.434). In addition, the size and the age composition of flocks did not change significantly with the change of the stages. In Caizi Lake, the Hooded cranes mainly distributed on the paddy fields and mudflats in the early stage, and concentrated in the paddy habitats in the middle and late stages. The foraging flock size had significant different on habitats (F2,169=11.745, P=0.000), while the age composition of the foraging flock had not distinctly changed (F2,169=2.779, P=0.065). In addition, the size and the age composition of flocks changed significantly in meadows and mudflats during the stages, while not significantly in paddy fields.The foraging strategies and flock patterns of Hooded cranes were flexible, which was the response to the degradation lake wetland on the spatial and temporal variations of food abundance and disturbances. By the traded off risks and costs, the cranes had flexible flock distributions and variety of foraging habitats to maximize the benefits and to improve their fitness.