Study On Food Habit Of Wintering Cygnus Columbianus In Dongting Lake

Dongting Lake is in the middle reaches of the Yangtze River in the South Bank of the Jingjiang River, It is an important lake wetland in the Yangtze River Basin, It is one of the most important international wetlands in China. At present, Dongting Lake is mainly divided into East Dongting Lake, South Dongting Lake and West Dongting Lake.The monsoon climate of the lake region is obvious, and the biological resources are rich. Every year attracts tens of thousands of waterfowl came here, It is an important habitat for migratory birds. Little swan is the second class, of protection bird of China, a common species in Dongting Lake. it belongs to the eastern Palaearctic subspecies population. Through the investigation of the habitat environment and the feeding habits of the little swan in Dongting Lake, The main results of this thesis are as follows:1. Every year, the little swan arrive at Dongting Lake in October and maximum at middle December, leaving during March-April. In recent years, The number of little swan in Dongting Lake is increased rapidly (Y=229.85X+231.75, R2=0.61) In 2014, the total number of little swans in Dongting Lake reached 3002. There are fluctuations in the annual amount of the little swan in Dongting Lake,2008,2011 and 2014 were the peak of the little swan. East Dongting Lake is the largest proportion of the number of swans in four protection zone, The number has accounted for 79.87% of the total in Dongting Lake.2. Little swan is an omnivorous bird. It is main food is Car ex, Phalaris arundinacea, Potamogeton crispus and other food in Dongting Lake. We can learn the Changes in little swan's feeding habits during the whole winter by Field observation and Fecal microscopic analysis in the East Dongting Lake. Carex is the little swan's basic foraging food in overwintering. The 13 little swan was poisoned gastric contents and 66 Little Swan feces for microscopic examination showed that the main food for Little Swan is Carex. Field observation found that the stable period of Little Swan feeding mainly potamogeton crispus. In ex period Little Swan feeding mainly Phalaris arundinacea.3. Take three rescued little swan make indoor captivity experiment by feeding Carex, Phalaris arundinacea and Potamogeton crispus to study the little swan's food preferences, feeding sites and the food intake. Little Swan to 3 kinds of food preference degree from high to low are Potamogeton crispus, Phalaris arundinacea, Carex. The main feeding sites is crispus leaf, Phalaris leaf and carex leaf, Little swan on the feeding amount is Phalaris arundinacea greater than Potamogeton crispus, Carex feeding amount is minimum. the little swan's food preferences, feeding sites and the food intake may related to the nutritional composition of the food.4. Detection of nutritional components in different parts of Little Swan 3 kinds of main food, the nutrition ingredient of Potamogeton crispus leaf and stem was the highest, followed by the Phalaris leaf, carex leaf, Phalaris stems and Carex roots.