Giant panda Chu Xin enjoys the birthday meal at the panda hall of Siberian Tiger Park in Changchun, northeast China's Jilin Province, July 30, 2020. A birthday party was held to celebrate the fourth birthday of giant pandas Chu Xin and Mu Yun on Thursday. (Xinhua/Lin Hong)

Giant panda Chu Xin enjoys the birthday meal at the panda hall of Siberian Tiger Park in Changchun, northeast China's Jilin Province, July 30, 2020. (Xinhua/Lin Hong)

Giant panda Chu Xin prepares to enjoy the birthday present at the panda hall of Siberian Tiger Park in Changchun, northeast China's Jilin Province, July 30, 2020. (Xinhua/Lin Hong)

Giant panda Chu Xin enjoys the birthday meal at the panda hall of Siberian Tiger Park in Changchun, northeast China's Jilin Province, July 30, 2020. (Xinhua/Lin Hong)

Giant panda Mu Yun opens the birthday present at the panda hall of Siberian Tiger Park in Changchun, northeast China's Jilin Province, July 30, 2020. (Xinhua/Lin Hong)

Giant panda Chu Xin has fun during the birthday party at the panda hall of Siberian Tiger Park in Changchun, northeast China's Jilin Province, July 30, 2020.  (Xinhua/Lin Hong)

Giant panda Mu Yun has fun during the birthday party at the panda hall of Siberian Tiger Park in Changchun, northeast China's Jilin Province, July 30, 2020. (Xinhua/Lin Hong)

Giant panda Chu Xin is seen during the birthday party at the panda hall of Siberian Tiger Park in Changchun, northeast China's Jilin Province, July 30, 2020.  (Xinhua/Lin Hong)

Giant panda Mu Yun opens the birthday present at the panda hall of Siberian Tiger Park in Changchun, northeast China's Jilin Province, July 30, 2020. (Xinhua/Lin Hong)

Giant panda Chu Xin prepares to eat bamboo at the panda hall of Siberian Tiger Park in Changchun, northeast China's Jilin Province, July 30, 2020.  (Xinhua/Lin Hong)