Migratory birds are spotted in the Yellow River Delta, Dongying city, Shandong province, Nov 17, 2016. [Photo/Xinhua]

JI'NAN - More than 100,000 rare migratory birds were spotted as of November in China's Yellow River Delta, a sign of improved environment in the region.

Experts at the Yellow River Delta national reserve said on Sunday that five species of crane were discovered. It is rare to see five species at the same time in one area, as there are only 15 crane species worldwide and nine in Asia.

Over 50 Pelecanus crispus, or the Dalmatian pelican, have lived at the reserve since the beginning of October. There are fewer than 100 of the birds in Asia.

Established in 1992, the 153,000-hectare reserve is located on the Yellow River estuary at Dongying City in East China's Shandong province.

The 5,464-kilometer Yellow River, the second longest river in China, originates on the Qinghai-Tibet Plateau and winds its way through eight provincial regions before reaching the Bohai Sea in Shandong.