Migratory bird flies over Junshan Mountain in Nantong. [Photo/Nantong Daily]

The Five Mountains area in Nantong has once again served as a key stopover for migrating birds of prey, with hundreds gathering before crossing the Yangtze River on their southward journey.

From late September to mid-October, large numbers of raptors circled above the hills, resting before continuing south. In early October, more than 500 gray-faced buzzards took flight together, forming a striking aerial procession known locally as an "eagle river".

The area, comprising five mountains along the Yangtze River, offers favorable conditions for migrating raptors. The mountains' slopes generate rising warm air currents that help birds conserve energy, while surrounding woodlands provide food and shelter.

Weather is another key factor. Rain and headwinds can delay crossings, causing birds to gather on the mountains. When conditions improve, they take off in large groups, creating a spectacular sight.

Many of the raptors arrive from breeding grounds across Northeast Asia, including Siberia, Mongolia, Northeast China, the Korean Peninsula and Japan. Most continue to Southeast Asia for the winter, while others stay along China's southern and southeastern coast.

At the Junshan Mountain's "ecological island" pilot zone, local authorities conduct long-term monitoring, recording species including gray-faced buzzards, crested honey buzzards and falcons.

Ongoing habitat restoration along the Yangtze River is helping provide safer resting grounds. Authorities also encourage birdwatchers and photographers to keep their distance and avoid disturbing the birds during migration.