Tourists watch giant panda cub Xiao Liwu during his first birthday celebration at the San Diego Zoo, California, the United States, on July 29, 2013. Zoo staff made a cake with ice, bamboo and some of the cub's favorite fruits and also boxes wrapped as gifts. The cub Xiao Liwu was born on July 29, 2012, as the sixth baby of its mother Bai Yun. [Photo/Xinhua]