Nuove analisi sulla migrazione post-riproduttiva del biancone Circaetus gallicus nell’Italia nord-occidentale

Abstract

The autumn migration of the short-toed eagle Circaetus gallicus was studied from 15th to 26th September, in 2005, 2006 and 2007, at three sites in NW Italy: Stura Valley (S Piedmont), Arenzano (W Liguria) and Apuane Alps (NW Tuscany). During this 3-year period, 746, 2085 and 2352 shorttoed eagles were respectively counted at these three sites: correlations in both time and migration volume were found between the Apuane Alps and Arenzano, but not with the Stura Valley, where the migrating populations are probably of different origins (N Italy, with some reports of birds moving SW already from sites in the NE regions of Italy). Interestingly, the significant counts at the Apuane Alps suggest that birds performing this circuitous migration may involve a rather wide area through Central and Southern Italy; moreover, occasional findings on the Adriatic side of Central Italy (birds heading NW) would seem to show that this circuitous migration may also have a degree of longitudinal extension. During the second half of September a fair proportion (<20% of the whole volume) of juveniles is regularly observed at both Apuane Alps and Arenzano sites, and their migration dates are very close to the main adult movement, in agreement with the strategy to follow the adults performed by a portion of the juveniles.