Abstract
The Rüppell's Vulture, formerly restricted to a strictly African distribution, has recently been classified as a Critically Endangered species worldwide. However, in recent decades, observations of the species in Europe, particularly in the south of Spain, have been on the rise. In this study, we conduct a diagnosis of the situation of this species in southern Europe through the analysis of the Sahel Precipitation Index (SPI) and Griffon Vulture autumn migration counts as quantitative measures, with the aim of identifying possible drivers of these changes and population trends. The analyses demonstrated that a number of Griffon Vultures during autumn passage through the Strait of Gibraltar, together with Sahel precipitation anomalies from the previous year, are the best predictors of the number of Rüppell's Vultures during autumn passage through the same strait in the following year, explaining 68.7% of the variance. The proportion of Griffon Vultures in the Sahel has markedly increased as populations of other vultures have declined. Under these circumstances, it seems more than likely that Rüppell's Vultures would be prone to moving to Europe, following Griffon Vultures. This effect has also been favored by increases in number of raining days and floods in the Sahel due to climate change, which can lead to escapes of Rüppell's Vultures outside their usual ranges. Under these circumstances, it appears likely that the Rüppell's Vulture will soon become a new species among European vultures.