Page 2 - Agostini_alii_2007

MARCH 2007 SHORT COMMUNICATIONS 57
J. Raptor Res. 41(1):57–61
E 2007 The Raptor Research Foundation, Inc.

FACTORS SHAPING PATHWAYS OF EUROPEAN HONEY-BUZZARDS (PERNIS APIVORUS)DURING SPRING
MIGRATION IN THE CENTRAL MEDITERRANEAN BASIN

1
NICOLANTONIO AGOSTINI, CARMELA CARDELLI, AND MARCO GUSTIN
LIPU (Lega Italiana Protezione Uccelli), Conservation Dep., Via Trento 49, 43100 Parma, Italy
KEY WORDS: European Honey-buzzard; Pernis apivorus; mi- of Levanzo and Favignana. This island is located in the
gration; navigation; orientation; water crossing; wind. northern half of the Channel of Sicily, ca. 130 km NE of
the Cap Bon Promontory (Tunisia, Fig. 1). Monte Falcone
During migration, European Honey-buzzards Pernis api-
is its highest point, at 686 m. The observation station was
vorus mostly use soaring flight, exploiting thermal currents
located at an altitude of ca. 500 m. Pantelleria is a volcanic
over land. Because thermals are almost absent over water,
island (84 km 2 ), approximately 110 km SW of western Si-
travelling there requires more energetically-expensive
cily and 70 km ESE of the Cap Bon Peninsula, in the
powered flight (Kerlinger 1989) and European Honey-buz-
southern half of the Channel of Sicily (Fig. 1). The obser-
zards are reluctant to undertake long sea crossings. How-
vation station was located along the western coast (Punta
ever, each spring, thousands of migrants wintering in west-
Fram) at an altitude of ca. 100 m. At this island the highest
central equatorial Africa cross the central Mediterranean
elevation inland (Montagna Grande) reaches 836 m. Like
to reach their breeding areas in central-eastern Europe
Pantelleria, Panarea is a volcanic island (3.5 km 2 ), located
(Cramp and Simmons 1980). During this sea crossing,
the migrants concentrate at a narrowest point (approx. approximately 65 km NW from the Straits of Messina
150 km) leaving the African mainland from the Cap Bon (Fig. 1). The observation station was at the island’s highest
point, ca. 400 m a.s.l. Finally, at the Straits of Messina the
Peninsula en route to western Sicily, and also later at the
observation station was located along the Sicilian slope,
Straits of Messina (Agostini et al. 1994a, 1994b, Agostini
over the Peloritani Mountains at an altitude of ca. 500 m.
and Logozzo 1998, Corso 2001, Agostini et al. 2006). More-
Previous studies made at the Cap Bon Promontory and
over, at least some of European Honey-buzzards crossing
at the islands of Marettimo, Ustica and Pantelleria, showed
this Mediterranean area use alternative paths, reaching the
that European Honey-buzzards of the same flock tended to
Italian Peninsula directly via Ustica and Lipari Islands
remain together in front of the water barrier because the
(Fig. 1; Panuccio et al. 2004, Agostini and Panuccio
first individuals making a decision (crossing or not) were
2005, Agostini et al. 2005a). In doing so, they undertake
followed by the others (Agostini et al. 1994a, 1994b, 2005a,
a further water crossing flying over the Tyrrhenian Sea,
2005b). Thus, a flock-member did not act and orient in-
bypassing the Straits of Messina. Unlike the Straits of Mes-
dependently. For this reason, in our statistical analysis, we
sina, where migrants are reported mostly during head
considered the flock as sampling unit to avoid pseudo-
winds (Agostini 1992), at Ustica, European Honey-buz-
replication of the data (Hurlbert 1984, see also Agostini
zards move through during tailwinds, making a faster
et al. 2005a, 2005b). To investigate the circadian pattern of
and energetically less-expensive flight over water (Agostini
migration, each observation day was divided into three
et al. 2005a). The aim of this study was to investigate fac-
time periods: morning (0800–1159 H), midday (1200–
tors shaping the pathways of European Honey-buzzards in
1559 H) and afternoon (1600–2000 H, solar time). Hourly
the central Mediterranean basin during spring migration
meteorological data from the two study areas (Pantelleria–
by simultaneous observations at four watch-sites, Maret-
Marettimo and Straits of Messina–Panarea) were recorded
timo, Pantelleria, Panarea (Lipari Islands) and the Straits at the meteorological stations of Pantelleria and Reggio
of Messina (Sicilian side).
Calabria, respectively, and obtained at the Italian web site
STUDY AREA AND METHODS of the Weather Underground Inc. (www.ilmeteo.it/dati.
htm). Observations were interrupted only because of rain
Observations, using binoculars and telescopes, were
and/or poor visibility. Contingency tables were used to test
made between 25 April–20 May 2004, the peak of the
the influence of prevailing winds and of the time of the
spring migration of the European Honey-buzzard in the
day on the migratory flow through the Channel of Sicily
Mediterranean basin (Cramp and Simmons 1980). Maret-
timo is a small (12 km 2 ) mountainous island, approximate- (Marettimo-Pantelleria) and eastern Sicily (Straits of Mes-
ly 30 km from western Sicily and 20 km west of the islands sina-Panarea).
RESULTS
1 Present address: Mediterranean Raptor Migration Net- Pantelleria–Marettimo. At these two sites, 325 flocks
work, Via Carlo Alberto 4, 89046 Marina di Gioiosa Jonica, (216 at Pantelleria, 109 at Marettimo) and 54 solitary in-
Italy; Email address: nicolantonioa@tiscalinet.it dividuals (19 at Pantelleria, 35 at Marettimo) were re-