GUIYANG, Dec. 22 (Xinhua) -- Environmental workers in Caohai Lake, the largest bird wintering ground in southwest China, have prepared sufficient food and a better environment for some 100,000 migratory birds.

Caohai National Nature Reserve in Guizhou Province added more than 80 hectares of plants, favored by the birds, earlier in the year.

"The nature reserve has seen a harvest of some plants now, such as 45,100 kg of potatoes and 6,500 kg of barnyard grasses," said Ran Jingcheng, an official with Guizhou Provincial Department of Forestry.

Caohai Lake has lots of aquatic flora. Its mild climate and intact natural environment make it an ideal place for flocks of rare transient birds and waterfowl.

It accommodates more than 100,000 migratory birds in the winter, including over 1,700 black-necked cranes, a rare fowl species on the verge of extinction, as well as hooded cranes, white storks, black storks, golden eagles and white-tailed sea eagles.

"Black-necked cranes usually fly to the lake between October and November and leave in March and April. We offer food for these migratory birds in the chilly winter months," Ran said.

In addition to providing food, workers at the nature reserve have also set up shelters for the birds with wood and dry grasses. They have also conducted bird flu monitoring in poultry raised by surrounding residents.

With strengthened environmental protection in recent years, the variety of birds living at Caohai Lake in winter has increased from 203 kinds a decade ago to 230 at present, with the number of birds increasing from 70,000 to 100,000.