Whooper swans prepare for their migration to Siberia in Rongcheng on Wednesday. [Photo by YANG ZHILI/FOR CHINA DAILY]

As the overall ecological system improved, many swans were seen not only in coastal towns but also in ponds and lakes in downtown Rongcheng, said Yu Bo, deputy head of Rongcheng's Haoyunjiao tourism development bureau.

"The number of places in Rongcheng where whooper swans like to gather has increased to more than 10 from two," Yu said.

People driving along the city's coastline can frequently see flocks of swans foraging for food and preening, he said.

"A good environment can attract more whooper swans to spend winter here and whooper swans will draw more tourists, generating more income for local farmers," Yu said.

More than 30,000 tourists visited Rongcheng to see whooper swans from November to the end of January, generating 6 million yuan ($950,000) in income, according to the bureau.

"Environmental protection and income growth form a sustainable circle," Yu said.

In addition to whooper swans, thousands of water birds live at the reserve the whole year.

"We must be very careful when we walk through grass during the birds' breeding period because eggs are hidden everywhere," Liu said.

Liu and his wife have recently been distributing corn where the swans live to provide enough food for those preparing to leave.

"We will be here waiting for them to return," Yu said.