The coexistence of the eagles Aquila chrysaetos and Hieraaetus fasciatus increases with low human population density, intermediate temperature, and high prey diversity

Competition among species with similar ecological requirements may preclude species coexistence. However, species with similar requirements may coexist under determinate environmental conditions. Major effort is being dedicated to conserve the golden eagle (Aquila chrysaetos) and Bonelli’s eagle (Hieraaetus fasciatus) in Spain, two raptors with similar ecological requirements. This work analyses how some key ecological factors correlate with the coexistence of the two eagles, which may help to optimize the conservation plannings of the two species. Findings show that low human population density favours eagle coexistence, because human presence is harmful for both eagles. Temperature is an important factor affecting the segregation of the two eagles, with Bonelli’s eagle dwelling in warmer zones than the golden eagle, but overlapping in squares with intermediate temperature. High prey diversity facilitates the coexistence of the two eagles, possibly because it encourages trophic segregation. Conservation planning for both species would be enhanced by the protection of zones with low human population density, intermediate temperature, and high prey diversity, which seem to favour the coexistence of the two eagles.