The population of Bonelli's eagle in Catalunya. Balance of year 2005

Recently finalized the year 2005 turns out interesting to make a synthesis of the state of the population of Bonelli's eagle in Catalunya. In principle it is possible to emphasize like a positive fact that a year plus the population seems to be stabilized, with a number that oscillates between 65 and 67 pairs. Although it is continued detecting the abandonment of some territory, this fact is compensated by the reoccupation of abandonned territories that has been detected in the last years.

As far as the productivity, already was commented in a previous news that this nesting season had been globally worse than those of previous years, although this one is a parameter that can oscillate much annually and that in addition has a smaller incidence than others in the demography of the species. It's thought that the great number of detected reproductive failures in 2005 in some of the Catalan population nuclei could be motivated by a very cold and dry winter 2004-2005. 

The estimation of the adult mortality, made from the disappearances and changes of animals observed with respect to the previous nesting season, indicates that this parameter approaches the values obtained during the last years and that, therefore, it continues being one of the important problems that it is precise to solve to guarantee the conservation of the species. One of the advantages that have supposed to carry out the radiotracking of adult birds of 15 different territories is to be able to locate and to recover the animals that die. Therefore, this last year has known the death of 5 eagles by collision with power lines, shots, predation by others raptors and breathlessness in rafts of prevention of forest fires.

This way it has been possible to obtain very valuable data on causes of mortality of the species that in normal conditions are difficult to detect and that they can have an importance superior to which in principle assumed. Another fact that is shown is the detected differences of mortality in the different distribution areas of the species where radiotracking is being made. It is possible to emphasize like very worrisome the mortality level that has occurred in 2005 in the population nucleus of the Montsant - Priorat (Tarragona). On the other hand, in the territories of the province of Barcelona is confirmed the reduction of the number of deaths of eagles observed in the last years. Another positive data is that have not occured electrocutations of eagles in the areas where electrical supports are being corrected of suitable way.

Finally it is also possible to emphasize like very positive data that every time are observed more nonadult eagles flying over occupied territories and that when the disappearance of an adult of a pair occurs, take place a substitution with relative rapidity. This one is a tendency that comes giving in the last years and that could indicate that the survival of the nonadult birds has been increased. This one could be the cause of which in the last years the Catalan population of Bonelli's eagle has become stabilized in spite of not being globally reduced a key demographic parameter as it is adult mortality.