GUIYANG, March 14 (Xinhua) -- Over 100,000 birds have started leaving a wetland in southwest China's Guizhou Province for their breeding grounds in the north.

Thanks to the additional food prepared by environmental workers at Caohai Lake, a major winter base for migratory birds in southwest China, the birds have survived the winter.

"Last October, we purchased 30 tonnes of corn before the birds arrived," said Qiu Jialing from the management committee of Caohai National Nature Reserve.

The reserve also cultivated more than 80 hectares of crops favored by the birds, such as potatoes, barnyard grasses, and white clover.

Zhao Qingjun, a wildlife ranger, scattered 60 kilograms of corn daily in the area he is responsible for. "If the weather is cold, the amount is doubled," he said.

The efforts at the reserve have paid off. A record high of nearly 1,700 black-necked cranes, a species classified as vulnerable on the International Union for Conservation of Nature (IUCN) red list, spent the winter at Caohai Lake last year.

The number of bird species seen at the lake during winter has increased from 203 a decade ago to 230 at present, with the number of birds increasing from 70,000 to 100,000.

"We hope to protect Caohai Lake and build a beautiful winter home for migratory birds," Zhao said.