Dades sobre la biologia de l'àliga cuabarrada ("Hieraaetus fasciatus" [Vieill.]) a la Serralada Pre-Litoral Catalana

This paper is based on the study of biology and ethology of the Bonelli's Eagle, namely of a couple from the Catalan Prelittoral range, with additional remarks on several other couples belonging to the same range. Bearing in mind that this species has already been studied by other authors, the aims of this study are, on the one hand, to gather data on aspects not studied so far, and on the other, to compare the obtained results with those of other authors from France, Castile, Navarra, Andalusia, while making available some of the first data on this species in Catalonia, where the eagle reaches one of the greatest densities in all Europe. The study is divided into two parts, of different length: out of breeding period and during the breeding period. The most important part is the breeding period, which begins when the eagles start preparing their nests, ending when the young ones become definitively independent. Therefore, we shall begin with prenuptial behaviour as restoring of nests and copulation until the laying of two eggs. The first egg was laid between the 26th II and 1st III, and the incubation lasted from 37 to 41 days for the first egg and 37 to 40 for the second. During the incubation period, done almost entirely by the female, green branches are brought in by the male and sometimes also by the female; we have also described behaviours already referred to by other authors, such as the turning of eggs, accommodation movement during the incubation and nest keeping. The first chick hatched between the 7th and 8th IV, while the second did it between the 9th and the 10th IV. During the breeding, behaviours such as covering, waste disposal, etc. were observed. In what feeding is concerned, we may emphasize that a 22 % of Oryctolagus cuniculus has been observed, a low percentage if compared to what has been observed by other authors, while Sciurus vulgaris, Columba palumbus and Lacerta lepida make up the 60 % of its diet. We also comment upon some observations of hunting, vocal activity and specific behaviour of the chicks, from allopreening to flight exercises, ending with their leaving the nest on 10th-11th VI (least feathered young, male) and 13th-14th VI (most feathered young, female); until the 30th VIII they were regularly observed in the breeding area