AVOCETTA - VOLUME 30 - N. 1/2
Esperienza di monitoraggio su vasta scala della migrazione autunnaledel biancone Circaetus gallicus in Italia e nel Mediterraneo centraleRUGGIERI L., PREMUDA G., BAGHINO L., GIRAUDO L.
Abstract:A large-scale survey of the autumn migration of shorttoed eagles Circaetus gallicus across Italy and the Central Mediterranean. In the present study, we report the results of a 5-year survey of the short-toed eagle Circaetus gallicus autumn migration from 41 watchsites. Of the 2761 individuals observed in active migration, 89.9% passed by 3 main watchsites (39.8% on the Apuane Alps, 33.5% at Arenzano and 16.5% in Stura Valley). Flight direction analysis at 14 minor watchsites located along the western slope of Apennines shows that the migratory route is directed mainly from SE to WNW in order to avoid the crossing of the northern Tyrrhenian Sea. Seventy percent of the migrants were adults, 20% were juveniles, and 10% older immatures. Analyses of 227 different migrating flocks where ageing was possible showed that 49.7% of the adult birds migrated alone, 31.6% together with other adults and 18.7% together with juveniles. Conversely, 30.7% of juveniles migrated alone, 6.4% together with other juveniles, and 61.2% together with one or more adults. This confirms that short-toed eagles migrate across Mediterranean basin by making a circuitous route towards France to avoid extensive sea crossing; moreover, our data suggest information transmission about the migration route, since a proportion of the juveniles appear to learn the migratory route by migrating together with the adults.