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546 N. Agostini et al.

barrier for raptor species, being between 3 and 12 vultures (Neophron percnopterus) attempting the
km wide (Agostini et al. 2015a). crossing of the Mediterranean Sea between south-
Our starting hypotheses are partially confirmed. ern Greece and North Africa (Oppel et al. 2015).
In particular the short-toed snake eagle, which is In reference to birds passing over Malta, their
the largest species regularly migrating in autumn at reluctance to continue migrating over the water
the site, is the only raptor showing substantial surface makes them more vulnerable to poaching,
reverse migration. This behavior could reflect the since they probably remain on the island longer
strong selective pressure of water barriers on short- than other migrating birds do (Del-Hoyo et al.
toed snake eagles which would be reluctant to 1994). In a recent paper, Panuccio et al. (2015)
continue migrating as soon as they approach even suggestedthatthe Italianpopulationofthe short-
relatively short stretches of sea (e.g. between toed snake eagle should be considered part of a
southern continental Italy and Eastern Sicily), metapopulation comprising those in Western
and even before reaching the coastline. This Europe (France, Spain). Small and peripheral
wouldhaveled to theevolution of theextremely populations of southern Italy could be considered
detoured path in birds breeding both in Italy and small patches of this metapopulation system cut off
Greece, favored by the partial overlap in the migra- from the bulk of the population of Western Europe
tion periods of individuals belonging to different (Panuccio et al. 2015). If this were the case, a high
age classes (Agostini et al. 2002; Panuccio et al. mortality of juveniles moving through southern
2012). Notably, nearly all short-toed snake eagles Italy and belonging to these small and periphery
breeding in Italy cross the Mediterranean Sea at patches could maintain a low density in the future,
the Strait of Gibraltar during both spring and despite the availability of suitable areas for this
autumn, probably retracing the colonization pro- species (Panuccio et al. 2015).
cess (Agostini & Mellone 2008;Panuccioetal.
2015). Most juveniles learn this flyway by follow-
Acknowledgements
ing adults (see also Mellone et al. 2016), while
some, migrating later in the season than older We appreciate the improvements in English
(experienced) birds, head southward passing usage made by Zoe Smith. MEDRAPTORS
along southern continental Italy and concentrating (www.raptormigration.org) is a network of
over the island of Marettimo (western Sicily; ornithologists promoting research and conserva-
Figure 1) located 130 km NE of the Cap Bon tion of migrating raptors. Finally, we wish to
promontory (Tunisia), and rarely also over Malta thank Antonino Morabito (Legambiente),
(Agostini et al. 2002; Sammut & Bonavia 2004; Eugenio Muscianese, Manuela Policastrese,
Mellone et al. 2016). Observations made over Elena Grasso, Giuseppe Camelliti, Francesco
Marettimo during autumn migration reported Polimeni, Andrea Ciulla, Giuseppe Martino,
tens of juveniles and few immature and adult Domenico Vitale, Ivan Zavettieri, Renzo Ientile,
birds hesitating in front of the open sea, sometimes Giuseppe Signorino, Michele Cento, Francesco
flying back toward the mainland (Agostini et al. Adragna, Simonetta Cutini, Angelo Scuderi,
2004, 2009; Panuccio et al. 2011). Such reversed Giovanni Cumbo, Antonietta Mascietti and
migration has been also recorded in a recent study Deborah Ricciardi (MAN) for their help during
made by satellite telemetry (Mellone et al. 2016). observations. Data collection as part of the mon-
In particular, two eagles tracked from their natal itoring activity of the post-reproductive migration
sites in southern Italy travelled two and three times of raptors in the Aspromonte National Park, sea-
between the Sicilian mainland and Marettimo and, sons 2011–2013, was planned and financed by the
finally, spent the winter in Sicily. The proportion Ente Nazionale Parco dell’Aspromonte.
of juveniles recorded in southern continental Italy
during this research is nearly the same as that
Funding
reported over Marettimo (between 79 and 95.8%;
Agostini et al. 2009; Panuccio et al. 2011). This work was partially supported by the the Ente
Considering the behavior here reported (as well Nazionale Parco dell’Aspromonte.
as at the island of Marettimo), and that at least
some birds winter in Sicily (Mascara 1985;
Supplemental data
Mellone et al. 2016), we suggest that many indivi-
duals heading south during autumn movements do The supplemental data for this article can be
not reach Africa, but interrupt their migration or accessed here: http://dx.doi.org/10.1080/11250003.
die during the crossing, such as juvenile Egyptian 2016.1240833.