A tourtist hangs a wishing sign on the Giant Panda Friendship Wall in San Diego Zoo in San Diego, the United States, April 6, 2019. The San Diego Zoo in the U.S. state of California held a special ceremony on Saturday to kick off a three-week farewell event for two giant pandas. Twenty-seven-year-old female giant panda Bai Yun and her son, six-year-old Xiao Liwu, will leave the zoo in late April and be sent back to China, as the zoo's conservation loan agreement with China has ended. (Xinhua/Li Ying)