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Panuccio et al. – Weather and Western Honey Buzzard Migration 655
travel speed as observed in other areas (Spaar use of soaring flight (Agostini and Logozzo 1995a),
1997). Regarding wind direction, Western and only a fraction of birds exhibit a light drift effect
Honey Buzzards passed mostly during periods when passing along the eastern corridor. These
of prevailing westerly rather than easterly winds, results partially agree with those made in Israel
since such atmospheric conditions are associated where Western Honey Buzzards migrating through
with the thermal-producing, fair-weather period that the Middle East use soaringgliding flight for 94%
follows the passage of a cold front in the central of their migration day and are therefore susceptible
Mediterranean region. For the same reason, the to drift (Shirihai and Christie 1992, Shirihai et al.
barometric pressure probably affected the altitude 2000).
of raptor flight. In addition, an approaching cold
front can cause unfavorable weather conditions Analyzing satellite telemetry data collected
(rain and southerly winds) north of the watch all along the migration route, Thorup et al. (2003)
points, just along the migratory flyway; Western showed that adult Western Honey Buzzards
Honey Buzzards that pass through southern compensate for wind drift and are less affected
continental Italy during autumn are most likely from than juveniles by crosswinds when migrating
breeding areas in central Italy and the Balkans over land. We suggest that adult Western Honey
via the Adriatic Sea (Agostini et al. 2007b). As Buzzards also tend to compensate for deviations
in our study, in eastern Pennsylvania, USA, the in lateral winds on a smaller scale when migrating
peak of raptor migration is associated with weather over land through this isthmus area. On the other
conditions that help create thermal updrafts on hand, as mentioned above, migrants will change
days following the passage of a cold front (Allen et their migration strategy in relation to wind drift
al. 1996, Maransky et al. 1997). There could be 2 when migrating through the Channel of Sicily
alternative explanations for the fact that migration en route to Africa by showing a broad front of
counts did not differ between times of low and high migration over water (Agostini et al. 2005).
barometric pressure, or weak and strong westerly
winds: within the different periods of the day (1) Unfortunately, in the last 3 yr, a proliferation
during ideal weather conditions for soaring flight of wind farms has occurred in our study area.
(high barometric pressure and weak lateral winds), Considering the flight strategies adopted by
a higher percentage of raptors passed through Western Honey Buzzards in particular during
undetected; or (2) migrants did not slow their travel strong lateral wind and low barometric pressure,
speed during unfavorable weather for soaring flight post-operam monitoring for possible mortality
when passing through the Marcellinara Isthmus, effects is recommended.
because they increased the use of powered
flight to limit the drift effect of lateral winds. The Acknowledgments: We wish to thank 2
1st explanation is not supported by the results anonymous referees for their useful comments
concerning the peak passage observed in the on an earlier version of this manuscript, and
afternoon, during better weather conditions for E. Grasso, P. Molina, M. Dech, P. Forconi, and
soaring flight; because of the flat and hilly zone S. Tarantino for their help during observations.
north of the site, approaching migrants cannot MEDRAPTORS (www.raptormigration.org),
use thermal and/or slope-soaring as raptors do a network of ornithologists and birdwatchers,
along a mountain ridge (Maransky et al. 1997), works to improve research and the protection of
and they are often flying close to the ground when migrating birds of prey through specific projects
they reach the study area (see also Agostini and and observation camps.
Logozzo 1995a b, 1997). Conversely, the latter
hypothesis would be in agreement with earlier REFERENCES
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made in the study area in the 1990s (Agostini pathways of European Honey-buzzards (Pernis apivorus)
and Logozzo 1995a) such as with our results during spring migration in the central Mediterranean
concerning the higher proportions of birds seen basin. J. Raptor Res. 41: 57-61.
passing at lower altitudes during both strong lateral
winds and low barometric pressure. In fact, during Agostini N, D Logozzo. 1995a. La migrazione autunnale del
such atmospheric conditions, Western Honey Falco pecchiaiolo sull’Appennino calabrese. Ricerche
Buzzards passing through the study area limit the biol. Selvaggina 22(Supplement): 511-512. (in Italian)
Agostini N, D Logozzo. 1995b. Autumn migration of Honey
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