Resumen de The expanding tree-nesting bonelli's eagle (aquila fasciata) population of southem portugal: habitat, demographic and dietary factors
Andreia Suzana de Pinho Dias Ribeiro e Cost
Bonelli's Eagle is considered an umbrella and flagship species in Mediterranean ecosystems. In this thesis, we focused on the fact that Bonelli´s eagle population of Southern Portugal presents a tree-nesting behaviour, different from the typical general cliff nesting features in the global range of the species, and has ecological, population and conservation implications. It is very important to study it in order to provide guidelines to assist in its conservation and in the management of species and/or populations with similar behaviour. When compare biometry, no different features were observed between tree-nesting population and the rest of the Iberian Peninsula and France so, Bonelli´s eagles did not show gradual size variations with ambient temperature, although there are marked features that have statistical significance (larger body length, wingspan, head length and width, tarsus width and tail length). These may represent an adaptation to forest environment or may be an amplification of some of the original forms of a small group of founders. Individuals from the tree nesting populations of Bonelli’s Eagle, consume more birds then individual that nest in cliffs. Taphonomy studies were conducted in Bonelli's Eagle for the first time, and tree-nesting individuals have also consumed greater number of birds. The way Bonelli's Eagles consume/break leporidae and birds´ bones, differs from other predators, allowing to detect its presence in archaeological sites and distinguish if nesting sites belong to this or another predator. Three-nesting population occupies a novel ecosystem that contains new combinations of species and landscapes that have emerged thanks to human action, namely eucalyptus. Nesting areas are associated with the areas of greater steepness, within the territories and may also be related to the presence of adequate trees for nesting with less human disturbance and also less affected by forest management. New observed colonizing pairs of Bonelli's Eagles, chose habitats that are structurally similar to those of the initial population nucleus, which may be a consequence of the imprinting on the part of the young of the original habitat conditions. The tree nesting seems to be an advantage since this ecological novelty permits the species to colonize new distribution areas and habitats previously unoccupied by the species with important ecological and conservation consequences.
