Griffon vultures (Gyps fulvus) circling in the sky in Sierra de Guara, Huesca, Aragon, Spain. The vulture population in Spain has plummeted since the introduction of European Union rules preventing farmers leaving dead carcasses on their land. Sierra de Guara is an official observation and monitoring site where once a week, the vultures are fed with carrion obtained from abattoirs and butchers. This opportunity is used by conservationists to count the number of vultures in the population.