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corded at the Cap Bon promontory by THIOLLAY (1975, 1977), DEJONGHE (1980) and HEIN
& KISLING (1991). In particular, among Accipitriformes, at the Straits of Messina nearly all
birds observed comprise Honey Buzzards, Marsh Harriers, Black Kites and Montagus
Harriers (Fig. 3a) while at Cap Bon notable concentrations of individuals belonging to
other species are also recorded (Fig. 3b). Studies on the water-crossing behaviour of mi-
grating raptors over the Tunisian promontory showed that the site is quite unsuitable even
for partial surveying (AGOSTINI & DUCHI 1994, AGOSTINI et al. 1994a, 1994b). In fact,
once raptors reach the coast near the promontory they rarely start the crossing, showing a
complex series of movements with individuals, for instance, returning to the coast after dis-
appearing over the sea and flying back inland. Because of this behaviour there is a risk of
re-counting the birds. For this reason the island of Marettimo is a better strategic point for
surveying the true migratory flow of Accipitriformes crossing the Channel of Sicily. In par-
ticular, counts made at the Straits of Messina and over Marettimo show that only rarely do
some Buzzards (Buteo buteo), Booted Eagles, Short-toed Eagles (Circaetus gallicus) and
Egyptian Vultures cross the central Mediterranean, while at the Cap Bon promontory nota-
ble concentrations of birds belonging to these species are recorded. In particular, THIOLLAY
(1977) estimated the passage, respectively, of more than 2,800, 450, 400 and 620 birds per
season. Moreover, at the Straits of Messina the Long-legged Buzzard (Buteo rufinus) and
the Lesser Spotted Eagle (Aquila pomarina) are irregular migrants (ZALLES & BILDSTEIN
2000) while the former author (1977) estimated a regular passage of more than 200 and 150
individuals. The numbers recorded at Cap Bon are probably the result of a recount of birds
belonging to the populations breeding and summering in Tunisia. These species do not
have high aspect ratio (long) wings and, for this reason, they are unlikely to undertake long
sea crossings (KERLINGER 1989). In the case of the Short-toed Eagle, the birds breeding in
central Italy cross the Mediterranean Sea at the Straits of Gibraltar, concentrating over the
Ligurian Apennines (northwest Italy, BAGHINO et al. 1987, AGOSTINI & MALARA 1997),
while the small population breeding in southern Italy perhaps mostly winters in Sicily
(MASCARA 1985, AGOSTINI & LOGOZZO 1997).
Fig. 3 - Composition of species observed (a) at the Straits of Messina during spring 1994 (N = 5,300;
AGOSTINI et al. 1995) and (b) at Cap Bon during spring 1990 (N = 8,928; HEIN & KISLING 1991,
quoted by ZALLES & BILDSTEIN 2000). HB - Honey Buzzard, BK - Black Kite, MH - Marsh Harrier,
MsH - Montagus Harrier, OS - other species.
Obr. 3 Skladba druhù pozorovaných (a) v úinì Messina bìhem jara 1994 (N = 5 300; AGOSTINI et al.
1995) a (b) na mysu Cap Bon bìhem jara 1990 (N = 8 928; HEIN & KISLING 1991 ex. ZALLES & BILDSTEIN
2000). HB - vèelojed lesní, BK - luòák hnìdý, MH - moták pochop, MsH - moták luní, OS - ostatní druhy.
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