Identifying key demographic parameters for the viability of a growing population of the endangered Egyptian Vulture Neophron percnopterus

The Egyptian Vulture Neophron percnopterus is a threatened species throughout its worldwide range. The Iberian Peninsula holds 50% of its global population, which has declined by 25% over the last 20 years. Despite this negative global trend, an increase in the number of individuals over the last 25 years has been observed in Catalonia, where it has colonised areas in which it was previously unknown. In this study, we describe the demographic evolution of an increasing population of Egyptian Vultures in central and eastern Catalonia and we apply population models and maximum likelihood procedures to investigate both the main demographic processes driving the observed trends and the viability of the population. The number of pairs in this region increased from one to 22 in the period 1988-2012. The best-supported models suggest that adult survival in this population may be higher than in other Iberian populations and that furthermore, there is a continuous influx of immigrants. Based on the most likely scenarios, Population Viability Analysis predicts that the population will continue to increase. Sensitivity analysis indicates that the adult survival rate has the greatest influence on population dynamics so conservation efforts will be more effective if concentrated on improving this rate.