Physical, environmental and human factors influencing productivity in Bonelli's eagle Hieraaetus fasciatus in Granada (SE Spain)

Abstract

We analysed the productivity of the Bonelli's eagle Hieraaetus fasciatus in relation to 26 variables that account for physiography, level of human presence, land-use, climate, laying date, and nest orientation, in the province of Granada (SE Spain), where a stable population exhibits the maximum productivity value for the species in Europe. Productivity positively correlated with cliff availability within territories and closeness of nest site to SE orientation. Cliff availability permitted some pairs to choose the best nest site orientation, thereby favouring high productivity. Nests in the preferred orientation (SE) had 35% higher productivity than those towards non-preferred orientations. Higher productivity in the best orientation nests might be related to warmer conditions. High productivity in the study area could offset the main problem for Bonelli's eagle conservation in Europe, that is, the high preadult and adult mortality. Actions required to ensure the recovery of neighbouring populations must focus on the preservation of high cliff availability and the diminution of preadult mortality in southeastern Spain. This would favour restocking of the decreased northern populations by the juvenile dispersion.