Gao Dali with the Eastern Dongting Lake Nature Reserve Administration says water is rising instead of receding as it usually does at this time of the year, Xinhua news agency reported.

The water level in the lake has risen about 20 feet this month to 92 feet, flooding wetlands that provide food for the birds, Gao said.

One worker at a nearby hydrological station said unusually heavy rains upstream are to blame.

Gao said there are more than 50,000 wild geese, 30,000 wild ducks and about 10,000 swans and cranes wintering at the lake.

The report said flocks of birds have been hovering and calling above the lake. Many other birds have been forced to visit nearby farms to feed, although their main diet includes weeds, fish and insects, instead of grain, experts said.