Restringido

Bonelli’s Eagle Hieraaetus fasciatus is one of the most endangered birds of prey in Europe. Despite mounting interest and research, several questions regarding the conservation
implications of territory occupancy and site-dependent population regulation remain insufficiently explored for this species. Here, we report on a 12-year study of the territorial
structure of a Bonelli’s Eagle population in southeastern Spain. No signals of population decline were found in the breeding population, as mean annual productivity was stable and
the presence of mixed-age pairs in the population decreased with the years. However, the average proportion of subadults occupying territories was larger than that observed in other
Spanish populations. Contrary to the predictions of a despotic distribution model, we found no significant relationship between occupancy rates and breeding parameters. Our results
showed significant variations in productivity attributable to differences in the quality of individuals (i.e. mixed versus adult pairs), but no variability among territories per se (i.e. caused by habitat heterogeneity). Moreover, coexistence with intraguild species did not have any significant effect on productivity, although the proximity of Eagle Owls Bubo bubo affected
the occupation rate of territories. Finally, our population does not appear to experience sitedependent population regulation, as a positive relation between mean annual productivity and density was found. The threat posed by changes in land use in the study area leads us to suggest that strict protection of current territories is necessary to ensure population persistence, and we suggest that a significant population increase is only likely if new or deserted territories become available.

Martínez, J.A., Calvo, J.F., Martínez, J.E., Zuberogoitia, I., Zabala, J., Redpath, S.M., 2008. Breeding performance, age effects and territory occupancy in a Bonelli´s Eagle Hiaraaetus fasciatus population. Ibis 150, 223-233.