Conservation Biology Group

Threats and solutions

New study on inter-populational movements and recruitment of Bonelli’s Eagle in Catalonia and France

The Conservation Biology Group, in collaboration with other French experts, conducted a study published in the journal The Auk, where a basic aspect of the life cycle and a key determinant of population dynamics, the recruitment, is analysed. Recruitment is the process by which individuals are incorporated into the reproductive segment of the population, and the factors that determine its dynamics are little known in bird species.

For its study, the Group carried out extensive field work over a period stretching from 1980 to 2007, with individual recognition of 451 chicks in the Iberian Peninsula and south-west France, where we find the largest populations of Bonelli’s eagles in Europe. The study shows that eagles are recruited into the population relatively late and that the global return rate of 10% is comparatively low, probably due to the high mortality rate during dispersion. In the study we state that recruitment depends on year of birth, parental quality and territory or origin, among other variables. Most movements between populations occur between the time that the eagles leave the nest and their recruitment into a territory. These movements connect local populations, and in the case of Bonelli’s eagles they are essential maintaining local populations of an endangered species. The study also shows that females disperse much further than males and that females in Catalan populations disperse more extensively than females belonging to populations in France.
The study, which received financial support from the Fundació Miquel Torres, provides new information with which to evaluate population viability and reveals that populations are connected across geographical boundaries. Therefore, there is no sense in managing populations individually. Endangered species have no boundaries, and conservation action is usually carried out at the local level.

If we want to increase the survival of this and other species, we must unify conservation strategies between different agents and different geographical areas.

For further information:

  • HERNÁNDEZ-MATÍAS, A., REAL, J., PRADEL, R., RAVAYROL, A., VINCENT-MARTIN, N., BOSCA, F. & CHEYLAN, G. 2010. Determinants of Territorial Recruitment in Bonelli's Eagle (Aquila fasciata) Populations. The Auk, 127, Issue 1: 173-184. doi: 10.1525/auk.2009.09143