HOHHOT, May 15 (Xinhua) -- Xing Xiaojun was overjoyed by what he saw through the telescope. Several hundred rare birds with a black-hooded head, white body and light grey wings were flying freely on an islet in the wetland.

"The relict gulls returned when the ice began to melt in early April. Some of them have already started nesting," said Xing, director of the administration of the Ordos Relict Gull Reserve in the city of Ordos, north China's Inner Mongolia Autonomous Region.

Last year, over 800 gulls came here, marking the first mass return of the migratory birds in 13 years. "This year, more than 2,000 have come," he said.

The gull is an endangered species and a national first-class protected animal. Most of its population winter in Bohai Bay in China. In spring, the birds fly to northwestern China, Mongolia and Kazakhstan.

"There were once nearly 16,000 gulls in the wetland here, accounting for over 60 percent of its total population in the world. And the water area was as large as 10 square km in the 1990s," he said.

However, since 2006, few nests of the species have been seen because the islets disappeared as the lake shrank.

"The water dried. How could a bird survive here?" recalled Song Qiulian, a herder who lives nearby.

To restore the ecosystem of the wetland, the city has adopted a series of measures in recent years.

In 2018, a water diversion line was put into use, diverting water to the wetland from the Yellow River. So far, a total of 16 million cubic meters of water has been diverted.

Dams and tourism facilities have also been removed to reduce the impact on the birds.

At present, the lake, with its water area up to 8.5 square km, has seen four islets formed and boosted the diversity of birds.

Over the past two years, more than 80 kinds of birds have come here to rest or reproduce. Especially in autumn, over 20,000 migrating birds visited the spot, showed monitoring statistics of the administration.

"We are very much encouraged by what we have seen, which has proved that we have been making efforts in the right direction," said Han Yufei, head of the city's forestry and grassland bureau. "I believe that this place will again become a haven for the birds to rest and reproduce as long as we continue our protective efforts."