XI'AN, April 6 (Xinhua) -- Wild birds in the Qinling Mountains in northwest China have thrived over the years thanks to intensified protection, authorities have said.

A total of 521 wild bird species have been discovered in the mountains, including 11 under Class One national protection, according to the Shaanxi Institute of Zoology.

Local authorities in northwestern Shaanxi Province have taken a variety of means to protect birds, including the crested ibis, which increased from merely seven in 1981 to more than 3,000, including about 2,600 in Qinling.

The Qinling Mountains are the natural boundary between north and south China. It is one of China's key areas of bio-diversity.