The pre-adult mortality is the percentage of young individuals that have died during the periods of emancipation and dispersion.

Once they go out of the nest, the young eagles are very inexpert and they begin a life full of risks in which only the most capable and strong survive. Likewise, this strategy of natural selection has turned out to be altered by the changes produced by men, who are the cause that in the last decades the pre-adult mortality is much higher. That's why every time it is more difficult for the young eagles to come to the adult age and be able to occupy the place of the dead adults.