Migratory egrets. [Photo/Yongpai App]

As spring arrives in Ningbo, a group of long-distance migratory birds has returned to the industrial complex of China Petroleum and Chemical Corporation Zhenhai Refining and Chemical Branch.

Nearly 100 herons — mainly night herons accompanied by little egrets — have recently appeared in the refinery's Egret Garden, marking the start of their breeding season.

Captured by the global livestream platform I-egret, the birds can be seen perched on branches, grooming their feathers and collecting twigs to build nests, quietly preparing to usher in their next generation.

These birds are remarkable travelers. In recent years, Zhenhai Refining and Chemical Branch has partnered with the Chinese Academy of Forestry's Research Institute of Subtropical Forestry to track the flock using satellite technology.

Researchers found their winter migration routes span China's Zhejiang, Fujian, Taiwan, Guangdong and Hainan, and extend to Southeast Asian countries including Vietnam, the Philippines, Malaysia and Indonesia.

The distance from Ningbo to Indonesia is about 4,000 kilometers one way, meaning the birds travel more than 10,000 kilometers annually. Detailed records of their routes and stopover sites have revealed that the flock follows a globally important migratory bird corridor.

Their yearly return reflects the improving ecological environment at the factory. The 15,000-square-meter Egret Garden has become a well-known bird-watching spot in Zhejiang and the first natural egret breeding habitat within a petroleum factory, showcasing a harmonious balance between industry and nature.

Egrets at the Egret Garden of China Petroleum and Chemical Corporation Zhenhai Refining and Chemical Branch. [Photo by He Wen/Yongpai App]