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Migration ecology of raptors in the Mediterranean
honey buzzards and very small flocks of harriers allows the transmission of information between
(paper X). When raptors approach the point where experienced and inexperienced individuals. In the
water crossing begins, their tendency to remain short-toed snake eagles this is particularly evident
in flocks become stronger. This is because raptors since, as mentioned before, they make a long detour.
often hesitate before undertaking a crossing and The high degree of synchronism in the migration
the larger the flock, the greater the chance that an period of juveniles and adults belonging to the
individual will begin crossing and that the others Greek population allows the formation of mixed-
will follow (Kerlinger 1989). This behaviour can age flocks. The percentage of juveniles migrating
easily be verified by comparing the migration of together with adults is higher in observations made
the same species in the same geographical area over in Greece compared with the ones recorded in
land and over water. As in the case of migrating Italy. Similarly, observations in southern Greece
black kites passing through southern Italy in have indicated a lower number of juvenile short-
autumn, as they migrate over the Apennines they toed snake eagles migrating later than adults, while
are usually observed moving in flocks of dozens across the Channel of Sicily the number of young
of individuals while on two islands of the Sicilian observed is larger. In addition, on the basis of data
Channel concentrations of up to one thousand collected for a single year in Greece (far more data
kites are regularly reported (Agostini et al. 2000, is available for Italy), I ventured the hypothesis
2004, Panuccio et al. 2005a, see also paper I). that the different proportion of juveniles observed
In the species studied, if we consider adult in Greece and in Italy might reflect the different
(experienced) individuals, only the western length of the crossing between Europe and Africa;
marsh harrier follows (mostly) its innate axis of indeed the distance between Greece and Libya is
migration (NE-SW, see paper II, III, IV). In the more than twice that of Italy and Tunisia. This
other species studied, adults use flyways that only hypothesis is formulated on the assumption that the
partly reflect their innate axis. Adult individuals width of the water barrier acts as a strong selective
display true navigation and orientation abilities, force. Moreover, I suggest that a relationship exists
modifying their direction of migration and between the size of the barrier and the tendency
changing their migratory behaviour in relation to of juveniles to follow adults as a result of a higher
weather conditions and ecological barriers (Hake mortality of short-toed snake eagles attempting to
et al. 2003, Agostini 2004). Flocking behaviour cross the Mediterranean between southern Greece
Figure 6 - Kythira island from Antikythira after the rain, October 2009.
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