A crested ibis flies near Chenjia Village of Yangxian County, northwest China's Shaanxi Province, Aug. 1, 2020. (Xinhua/Lan Hongguang)

Sixteen Japan-born crested ibises, offspring of birds originally sent from China, officially settled at Beijing Zoo on Wednesday after completing a month-long quarantine.

These birds, a first-class national protected species, will now live and breed alongside the zoo's existing population of 23 crested ibises, according to the zoo.

Mao Yu, head of the zoo's crested ibis team, said that they had made thorough preparations for the arrival of the flock. "We disinfected and cleaned their enclosures thoroughly, and provided them with suitable food such as loach, beef strips, and mealworms," Mao said.

Mao, who has been working with crested ibises for 23 years, has accompanied these birds since their quarantine period began. "Crested ibises are naturally timid and sensitive to noise; even the smallest disturbance can startle them. I hope that during this time, they will become familiar with me," he added.

Zheng Changming, head of the zoo's species management department, said that Beijing Zoo hatched its first artificial-breeding crested ibis in 1989. With the addition of the returned birds, the zoo's population has reached 39.

The crested ibis was once on the brink of extinction. In 1981, only seven wild crested ibises were found in Yangxian, northwest China's Shaanxi Province. Over the past four decades of conservation efforts, the global population of such birds has now surpassed 10,000.

The 16 crested ibises were airlifted to Beijing on Oct. 31.