Migratory birds are seen in the Qilihai wetland nature reserve in Ninghe District of north China's Tianjin, March 2, 2022. Qilihai Wetland, an important stopover site for migratory birds, has improved its environmental quality and ecological service function in recent years. (Xinhua/Sun Fanyue)

　　Migratory birds are seen in the Qilihai wetland nature reserve in Ninghe District of north China's Tianjin, March 2, 2022. Qilihai Wetland, an important stopover site for migratory birds, has improved its environmental quality and ecological service function in recent years. (Xinhua/Sun Fanyue)

　　Migratory birds are seen in the Qilihai wetland nature reserve in Ninghe District of north China's Tianjin, March 2, 2022. Qilihai Wetland, an important stopover site for migratory birds, has improved its environmental quality and ecological service function in recent years. (Xinhua/Sun Fanyue)

　　Migratory birds are seen in the Qilihai wetland nature reserve in Ninghe District of north China's Tianjin, March 2, 2022. Qilihai Wetland, an important stopover site for migratory birds, has improved its environmental quality and ecological service function in recent years. (Xinhua/Sun Fanyue)