The birder recording Beijing's wildest sounds

Paul Holt knows Beijing's tweets like the back of his hand. In his more than two decades living in China, the British ornithologist has recorded 80,000 bird calls, now archived at the British Library. Let's join Paul in listening to what our feathered friends are chirping about over Beijing. (Produced by Wang Ruofan, Di Jingyuan, Ni Tao, Wang Xiangyu, intern Zhang Sisi, Yang Ziyu and Tian Yanan)