Experimental food subsidies keep eagles inside protected areas: implications for conservation and resource management

The conservation and management of mobile species, populations and dynamic habitats, presents significant challenges since such species face diverse threats during various stages of their life cycle. Protected areas (PAs) are essential tools in conservation efforts, aiming to preserve native species and their habitats. However, larger mobile animals, such as the Bonelli's eagle (Aquila fasciata), may require much larger areas outside PAs for essential life moments, including foraging, resting, and wintering. As a result, the efficacy of PAs in conserving such species may be questionable. We designed an experiment in an eastern Spain PA that is home to nesting Bonelli's eagles to determine if increasing food availability through experimental feeding within the PA could result in an effective reduction of space use outside the protected area by the eagles and lead to reduce death risk. Over the period of 2016 to 2021, we tracked 10 Bonelli's eagles from six different territories using GPS-GSM transmitters. We evaluated their space use before, during, and after the feeding experiment. Our results indicate that the availability of food within PAs restricted the eagles' movement, resulting in a higher concentration of locations inside the PAs. The eagles spent less time outside the PAs when they were fed and less time in highly human-dominated habitats. Consequently, this reduced mortality risks that were higher outside the PAs. Our findings suggest that management decisions aimed at increasing food availability within PAs, could be critical in conserving endangered species populations such as the Bonelli's eagle in Mediterranean landscapes.

Fieldwork seasons (2017 – 2018) were partially supported by the Wildlife Service of the Valencian Community Regional Government (Conselleria d'Agricultura, Desenvolupament Rural, Emergència Climàtica i Transició Ecològica, Generalitat Valenciana, Spain). Red Eléctrica de España provided financial support to track Bonelli's eagles under the supplementary feeding project. The corresponding author A. L-P. is supported by a Val I+D predoctoral grant (ACIF/2020/051) and an internship grant (CIBEFP/2021/75), both funded by the Generalitat Valenciana (Spain). This paper is part of the Ph.D. thesis of A. López-Peinado at the University of Valencia (Spain).