HARBIN, Aug. 20 -- An oriental white stork is just a rare bird in most people's eyes, but for Zhao Zhichun, Katyusha is one of his closest friends, even a "lover".

People often see the stork flying over Khanka Lake to a research station on the shore, where she awaits the appearance of Zhao.

Born in northeast China's Jilin province, Zhao, 43, is an expert in wetland monitoring at Khanka Lake research station of Chinese Academy of Sciences, in neighboring Heilongjiang Province.

According to Zhao, the oriental white stork is a reserved and shy creature that humans hardly ever get close to, but Katyusha seems quite intimate with her human friend and comes when Zhao whistles, like an airborne dog. When he approaches Katyusha, she becomes very calm and quiet, just as if she is enjoying a sweet moment with her lover.

Their romance began in Nov. 2013 when Katyusha was rescued by locals living around the Qixing River National Nature Reserve and taken to the research station. Katyusha's wings had been injured, but Zhao and his colleagues nursed her back to health and have been taking care of her ever since.

Katyusha is now about two or three years old. An ordinary oriental white stork lives for more than ten years. Its diet consists mainly of fish, frogs and insects. She mainly lives on Khanka Lake, on the border between China and Russia, so the staff named her "Katyusha", an Russian girl's name.

Due to habitat loss and environmental change along its migration route, there are only about 2,000 oriental white storks left in the wild, mainly in Russia and China. The bird is a first-class nationally protected animal in China.

Storks usually migrate in November from Russia and northeast China to the middle and lower reaches of the Yangtze River and return in the spring.

Katyusha is practicing long-distance flying and storing energy like other birds, preparing for a trip due to start in two months, but maybe Katyusha does not want to part from her "lover" on the side of Khanka Lake, and Zhao is also reluctant to see her leave.

"I hope she finds a quiet and clean habitat and lives an elegant and happy life," said Zhao.