Every year, in the small village of Coyllurqui in the Peruvian Andes, locals celebrate the Yawar Festival. It's a striking spectacle as a condor is strapped to the back of a bull - so the two can fight it out. For locals, the fight symbolizes a re-enactment of their liberation from Spanish rule. For conservationists, it's yet another threat to one of the world's largest birds.