MIGRATION AND NATAL DISPERSAL IN THE BARN SWALLOW HIRUNDO RUSTICA

The present thesis investigates different aspects of the two main movements of birds - migration and natal dispersal - using the barn swallow Hirundo rustica as an ideal model species. First, the dissertation provides novel findings about the migration of this long-distance migratory bird, one of the phenomena that have fascinated people since ancient times. I successfully used a new technology, based on light-level ‘geolocators’, by which I could gather more information on the migration of barn swallows than it could be collected over more than one century of intense ringing activity of this species. Moreover, the present work also gives an important contribution to the evaluation of possible drawbacks of this technology, for passerines in general, and for aerially insectivorours species, which may be particularly susceptible to geolocator deployment, in particular. Second, I studied natal dispersal in barn swallows, giving a fundamental contribution to the knowledge of this ecological process from different points of view, and identifying several factors that affect dispersal decisions and that act at different scale and stage of the individual life history. Both the results on migration and on natal dispersal may have also a great importance in order to plan appropriate conservation measures at the breeding sites and on the wintering grounds. Indeed, several barn swallow geographical populations, including the ones I studied, are declining, probably as a result of diverse factors that act both in breeding and in the wintering areas. The detailed knowledge of the geographical positions and movements in the non-breeding areas and along the migration routes is the first and indispensable step to program interventions of conservation in the wintering areas. In the breeding sites, for instance, I have demonstrated that the presence of livestock is a key factor for the local recruitment of young; so its maintenance in the farms may contribute to buffering the population decline of this species. Hence, my findings on the two topics can have in the future also a practical application for the conservation of the breeding populations of this declining, flagship bird species.