HARBIN, Aug. 1 -- Sixty-seven red-crowned cranes were hatched this year in Zhalong National Nature Reserve, the world's largest captive breeding center for the endangered bird species, in northeast China's Heilongjiang Province.

Around 1,000 red-crowned cranes have been artificially bred in the Zhalong reserve, set up in 1979 and covering an area of 2,100 square kilometers in China's largest reed wetland.

The reserve has been exploring ways to train the captive-bred cranes for release into the wild to raise the crane population with a healthy genetic pedigree. More than 300 cranes have been released and the population of red-crowned cranes in the reserve currently stands at around 500.

The reserve started to place ring marks on the birds' legs to avoid inbreeding in 2002 and has diverted 2.9 billion cubic meters of water from nearby rivers to prevent wetland degradation.

Red-crowned cranes are usually found in northeast China, Russia, Japan, South Korea and the Democratic People's Republic of Korea. There are around 2,400 red-crowned cranes living in the wild worldwide.