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Marsh Harrier and Honey Buzzard migration in Eastern Mediterranean
dimensionless term used to compare the shape of overcoming sea barriers (Kerlinger 1989, Panuccio
the wings of birds: in general, species with longer and Agostini 2010).
and narrower wings are better suited to powered We made simultaneous observations at two sites in
flapping flight (Kerlinger 1989). The behaviour the Central-Eastern Mediterranean and analysed
shown by raptors during the crossing of water differences in timing, age and sex. Finally, since
barriers also varies among species according to sea-crossings are crucial during migration, the
the different morphologic features just explained. effect of lateral winds on the intensity of the
The most common raptor species that cross migratory flow of the two species at the island
the Mediterranean Sea are: the Western Marsh of Antikythira was also investigated. Indeed, the
Harrier (Circus aeruginosus) and the European resulting path of a flying bird is largely influenced
Honey Buzzard (Pernis apivorus; Finlayson, 1992; by wind direction. Winds perpendicular to the
Rebassa, 1995; Zalles & Bildstein, 2000; Agostini direction in which the bird is moving can cause
et al., 2002, 2003; Sammut & Bonavia, 2004; a shift in the birds’ path. This effect is called wind
Panuccio et al., 2005a; Kirwan et al., 2008; drift and many species of migrating birds are able
Agostini & Panuccio, 2010). to compensate it (Klaassen et al., 2010b)
These two species exhibit different water crossing The aims of this research are to: 1) investigate
patterns. Studies based on satellite telemetry, differences in the water crossing tendency of
radar, direct observations and band recovery Western Marsh Harriers and European Honey
data substantially agree that during their autumn Buzzards along a route where information is
migration Western Marsh Harriers undertake long lacking and check whether the two migratory
water crossings, heading in a SSW-SW direction patterns previously observed can be generalised;
and crossing the Mediterranean mostly during the 2) discuss hypotheses which may explain the
second and last third of September (for a review migration strategies observed. In order to test
see Agostini & Panuccio, 2010). It overlaps during the role of morphologic differences between
the same period with the migration of juvenile the two species we used a computer simulation
European Honey Buzzards, however the latter providing information on the two species’ energy
appears more reluctant than harriers to use powered consumption rates during both powered flapping
flight (Kerlinger, 1989). As a result, juvenile and soaring gliding flight.
European Honey Buzzards tend to follow leading Materials and methods
lines and also modify their migratory direction Fieldwork
depending on landmarks (i.e. coasts, promontories Observations were made simultaneously at the
and islands). This behavior was reported between island of Antikythira (southern Greece) and at
Central Italy and the island of Malta where, unlike Mount Olympus (northern Greece) from 9th
Western Marsh Harriers, hundreds of European September to 1st October 2009, a period during
Honey Buzzards, after initiating sea crossing at the which the migration of Western Marsh Harriers
Circeo Promontory, deviate eastward to follow and juvenile European Honey Buzzards overlaps
the Italian peninsula, flying a couple of days later (Agostini et al., 2002, 2003, 2004). A total of 207
over the island of Malta (Agostini et al., 2002, hours of fieldwork was undertaken at the two sites
2004). To date, there is a dearth of information from 9:00 (solar time) until dusk, with the aid of
available on raptor migration along the Central- binoculars and telescopes.
Eastern Mediterranean flyway (Lucia et al. 2011) Antikythira (35° 52’ N; 23° 18’ E) is a small island
and previous comparative studies on the water- (20 km²; max. altitude 378 m), oriented in a NW-
crossing tendency of Western Marsh Harriers and SE direction, located 32 km SE of the island of
European Honey Buzzards have described their Kythira, 59 km S of the Peloponnesus Peninsula
behaviors at one sinlge watchsite. In addition, and 33 km NW of Crete which in turn is located
the aspect ratio was considered the main element approximately 300 km NE of the Cyrenaica
accounting for the different migration strategies in
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