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THE RING 27, 2 (2005) 217

pari Islands (Fig. 1). In particular, during springs 2001-2002 a maximum of about
2000 Honey Buzzards were reported over Ustica (Panuccio et al. 2004, Agostini et
al. 2005a) while between 20 April and 20 May 2004-2005 a maximum of 4420 birds
were observed via the island of Panarea (the Lipari Islands; Fig. 1, Gustin 2005,
Gustin et al. 2005). During spring 2004 more than 11 000 Honey Buzzards crossed
the Strait of Messina at its narrowest point, and both at the Strait and over Panarea
the peak of migration occurred on 11 May (Panuccio and Agostini 2005, Gustin et
al. 2005); thus migrants showed a high degree of synchronism at these two sites as
can be expected from this species which is well known for the condensed migration
period of adults with males and females reaching together their breeding areas
(Cramp and Simmons 1980, Gensbøl 1992).
During autumn migration adult Honey Buzzards cross the Central Mediterra-
nean between the end of August and the first ten days of September (Agostini and
Logozzo 1995, 1997). In this period their passage is less conspicuous: while an aver-
age number of 20 473 ± 1941 (SE) individuals was reported during springs
1996-2000 at the Strait of Messina (Corso 2001), on average 6714 ± 640 (SE) were
counted at the same site during autumn 2002-2004 (Panuccio et al. 2005, Repaci and
Morabito pers. obs.). Thus, as suggested by Agostini and Logozzo (1995), thou-
sands of adults regularly use two different routes each year. Moreover, birds cross-
ing the central Mediterranean during autumn avoid the long crossing of the Tyrrhe-
nian Sea. In particular, few adult birds have been recorded leaving the western
slope of the Italian Peninsula from the Circeo promontory and via the island of Ca-
pri, while over Ustica and Panarea their post-reproductive passage is virtually non-
existent (Jonzén and Pettersson 1999, Agostini et al. 2003, Agostini et al. 2004a, Pa-
nuccio et al. 2005). In this period, adult Honey Buzzards follow the Italian mainland
and northern Sicily concentrating at the Strait of Messina; they reach Africa
through the Channel of Sicily, at least part of them via Marettimo and Pantelleria
islands, like during spring migration (Fig. 1, Agostini and Logozzo 1997, Agostini et
al. 2000, Agostini et al. 2004b, 2005b). It is interesting to note that adult Honey Buz-
zards passing via Pantelleria choose the shortest flyway over water to reach Africa,
changing their orientation behaviour leaving the island heading WNW. They make
a curvilinear migration over water applying true navigational abilities, Tunisia
nearly always being out of sight. Unlike adults, large numbers of juvenile Honey
Buzzards undertake sea crossings through the central Mediterranean during
autumn migration, probably moving along NE-SW innate axis (Agostini 2004,
Agostini et al. 1999, Agostini et al. 2002, Agostini et al. 2004a). Since juveniles tend
to migrate about two weeks later than adults during their first migration (Kjellén
1992, Agostini and Logozzo 1995) they probably move along innate directions of
migration and, with some exception, they cannot learn the shortest route over sea to
cross the Mediterranean by following adults (Agostini 2004, Agostini et al. 1999,
Agostini et al. 2000, Agostini et al. 2002, Agostini et al. 2004a).
Why is the passage of adult Honey Buzzards across the central Mediterranean
less conspicuous during autumn migration? Why do adults show a stronger ten-