Page 2 - Panuccio_et_al_002

272 Kurze Mitteilungen l Di<
Vogelwlll1e

Capri and Marettirno (CORBI et al. 1999, ]ONZÉN & PETTERSSON 1999, AGOSTINI et al. 2001). Observa-
tions on the migratory flow ofthis species across the Tyrrhenian Sea during spring are 1acking. The aim
of this study was to investigate the spring migration of Marsh Harriers across the Tyrrhenian Sea both
in re1ation to wind conditions and sex c1asses by observations over the is1and ofUstica (western Sicily).
Study area and methods
Ustica is a small island (8.5 Jcrn2) about60 km N ofwestem Sicily, 270 km NE ofthe Cap Bon promontory (Tunisia),
140 km NE ofthe island ofMarettimo and 230 km W ofthe ltalian peninsula (Fig. l}. A total of234 h ofobserva-
tions (9 h per day), with l O X 40 binoculars, were made between 22 Mare h and 16 Aprii 2002, the peak period of
the spring migration ofthis species on the Mediterranean basin (CRAMP & StMMONS 1980, AGOSTINI & Looozzo
2000). The observation post was at the highest point (approx. ISO m) ofthe promontory dominating the NE coast
of the island (its highest point, inland, reaching about 250 m). From this post i t was possible to detect birds under-
taking the crossing oftheTyrrhenian Sea. Each day was divided in three periods: moming (09.00-12.00 h), midday
( 12.00-15.00) and aftemoon (IS.OQ-18.00; solar ti me). Hourly meteorologica! data from Ustica were provided by
the ltalian Air Force. It was possible to determine the age and sex of 294 birds by observation of their plumage
(FORSMAN 1999). The total of mal es, femalcs and juveniles was derived by multiplying their proportions in thc sam-
ple of identified individuals, following the method used by KIELLÉN ( 1992) at Falsterbo (Sweden). In particular, to
exclude a bias due to the better identification of adult mal es, the proportion of females andjuveniles was estimated
dividing unidentified individuals of the group female/juvenile between the two age groups according to their pro-
portion among the identified birds (see al so AOOSTINI & Looozzo 2000, AOOSTINI 200 ), AOOSTiNI et al. 200 l).
Acknowledgements: This research has been partially made within the activities of the Stazione di Inanel-
lamento of Palermo, funded by the Assessorato Agricoltura e Foreste of the Regione Siciliana. We are grate fui
to the Istituto Nazionale per la Meteorologia for its helpful collaboration.

Tyrrhenlan Sea

Ustica:

..

• • Malta

Fig. 1: The study area.
Abb, 1: Die Beobachtungsregion.