ZHENGZHOU -- About 20 swans have arrived at Sanmenxia Swan Lake Wetland Park in Sanmenxia city, Central China's Henan province, the park administrator said Tuesday.

Every year, the migratory swans come from Siberia to spend the winter.

"The swans were resting on the lake, finding food there. The park patrolmen have been looking after them," a park employee said.

"The first group of swans arrived earlier this year, possibly due to the cold front," said Zhang Mingyun, head of the Sanmenxia swan protection association. "More swans will come in the next two to three months."

The park has seen an increase in the number of swans during the annual migration season from November to March. Over 60 percent of all swans who winter in China choose the city, earning it the reputation as "the city of swans."

Sanmenxia wetland is fed by the Yellow River, which decades ago was dirty and polluted, with only a handful of swans braving the waters.

In 2011, Sanmenxia began work on the Yellow River Wetland Park, part of the wider Yellow River National Nature Reserve.