Possible functions of alternative nests in raptors: the case of Bonelli’s Eagle

摘要: Four non-exclusive hypotheses have been proposed to explain the alternative nest-building behaviour of raptors: (1) nests as an advertising signal in territories, (2) frustration nests, (3) competition avoidance by nest-site and (4) reduction nest ectoparasites. We report here data collected during observational study a population Bonelli’s Eagle Hieraaetus fasciatus southeastern Spain. Our does not support first two based on closeness within lack correlation between number distance neighbours construction secondary at similar frequencies after breeding failures successes. In contrast, avoid with other cliff-nesting raptor species nearby was clearly important since 30% pairs obtained some direct benefit from existence their territories. also found abundant Coleoptera (Dermestidae) Diptera (Carnidae, Calliphoridae Phoridae) ectoparasites use synergetically presence greenery mechanisms for avoiding ectoparasites, factor success eagle. suggest that and, particular, ectoparasite are more plausible explanations maintenance raptors.