Aerial photo taken on April 17, 2020 shows a view of Jixi national wetland park in the west of Jinan, capital of east China's Shandong Province. (Xinhua/Guo Xulei)

Aerial photo taken on April 17, 2020 shows a view of Jixi national wetland park in the west of Jinan, capital of east China's Shandong Province. (Xinhua/Guo Xulei)

Aerial photo taken on April 17, 2020 shows a view of Jixi national wetland park in the west of Jinan, capital of east China's Shandong Province. (Xinhua/Guo Xulei)

Aerial photo taken on April 17, 2020 shows a view of Jixi national wetland park in the west of Jinan, capital of east China's Shandong Province. (Xinhua/Guo Xulei)

Aerial photo taken on April 17, 2020 shows a view of Jixi national wetland park in the west of Jinan, capital of east China's Shandong Province. (Xinhua/Guo Xulei)

Aerial photo taken on April 17, 2020 shows a view of Jixi national wetland park in the west of Jinan, capital of east China's Shandong Province. (Xinhua/Guo Xulei)

Aerial photo taken on April 17, 2020 shows a view of Jixi national wetland park in the west of Jinan, capital of east China's Shandong Province. (Xinhua/Guo Xulei)

Aerial photo taken on April 17, 2020 shows a view of Jixi national wetland park in the west of Jinan, capital of east China's Shandong Province. (Xinhua/Guo Xulei)