In this special Age of Extinction mini-series from Science Weekly, Guardian biodiversity reporter Phoebe Weston explores the murky world of the illegal killing of birds of prey on grouse moors, and asks why it is so difficult to solve these crimes. In episode two, Phoebe speaks to the people trying to protect these rare birds, but as she digs deeper encounters a surprising silence around the killing of Susie’s chicks. Help support our independent journalism at theguardian.com/sciencepod