Spatio-temporal variations in mortality causes of two migratory forest raptors in Spain

Abstract

Analysis of the 949 and 434 cases of mortality of Booted Eagle Aquila pennata and Short-toed Snake Eagle Circaetus gallicus, respectively, recorded by wildlife rehabilitation centres in Spain over a 16-year period (1990–2006) shows that power lines (19.5 and 35.2 %, respectively) and killing (32.5 and 22.9 %, respectively) were the main known causes of death. Multinomial regression models were used to analyse geographical and temporal variations in the causes of death. For the Booted Eagle, both factors (zone and year) were statistically significant, while there were only significant temporal variations for the Short-toed Snake Eagle. In the Booted Eagle, killing occurred more frequently than expected in the east and north of the country compared to the other Spanish regions. Power line casualties were significantly more frequent in the southern and eastern regions, and less common in the north. In both species, the multinomial models indicate that while the number of cases of killing significantly decreased during the 16 years studied, power line casualties increased. Our study suggests that human-induced mortality continues to be the main factor contributing to mortality for Spanish Booted Eagles and Short-toed Snake Eagles. Since a reduction in the mortality caused by human activities is a priority in the conservation strategies for raptor species, management guidelines are discussed.