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 one, Phoebe hears about the case of Susie, a hen harrier whose chicks were killed while being monitored on camera. As she starts to investigate the case, she hears from conservationist Ruth Tingay about why hen harriers are targeted and finds out about the personal costs of campaigning on this issue. Help support our independent journalism at theguardian.com/sciencepod