This aerial photo taken on Dec. 25, 2021 shows birds flying at the Yellow River Delta National Nature Reserve in east China's Shandong Province. The Yellow River Delta National Nature Reserve, a wetland nature reserve mainly aiming at protecting the ecosystem and rare and endangered birds at the river's estuary, was listed in 2013 on the Ramsar Convention on Wetlands of International Importance. (Photo by Yang Bin/Xinhua)

This aerial photo taken on Oct. 18, 2022 shows scenery at the Yellow River Delta National Nature Reserve in east China's Shandong Province. The Yellow River Delta National Nature Reserve, a wetland nature reserve mainly aiming at protecting the ecosystem and rare and endangered birds at the river's estuary, was listed in 2013 on the Ramsar Convention on Wetlands of International Importance. (Xinhua/Guo Xulei)

This aerial photo taken on Oct. 18, 2022 shows scenery at the Yellow River Delta National Nature Reserve in east China's Shandong Province. The Yellow River Delta National Nature Reserve, a wetland nature reserve mainly aiming at protecting the ecosystem and rare and endangered birds at the river's estuary, was listed in 2013 on the Ramsar Convention on Wetlands of International Importance. (Xinhua/Guo Xulei)

This aerial photo taken on Oct. 18, 2022 shows scenery at the Yellow River Delta National Nature Reserve in east China's Shandong Province. The Yellow River Delta National Nature Reserve, a wetland nature reserve mainly aiming at protecting the ecosystem and rare and endangered birds at the river's estuary, was listed in 2013 on the Ramsar Convention on Wetlands of International Importance. (Xinhua/Guo Xulei)