婉转，清丽，高亢，鸟儿在枝头欢唱。世界自然纪录片之父爱登堡老爵爷讲述鸟类鸣叫对于种群的意义。 　　David Attenborough chooses seven of the most remarkable animal songs found in nature and explores the significance of these songs in the lives of their species.