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Southbound direction of colonization of Short-toed Snake Eagle
underlines that the presence of Short-toed Snake Methods
Eagle is linked to forests for nest building and to Study area:
open areas like pasturelands and cultivation for The study area is Italy (301.302 km²) including the
forage activity (Bakaloudis et al. 1998, 2005). The large islands of Sicily and Sardinia. In this country
European population of Short-toed Snake Eagle is on the first of January 2010 the human population
evaluated in less than 10.000 pairs and its status is was 60.340.328 (ISTAT, website: http://demo.
Rare, in fact its low reproductive rate and high diet istat.it/pop2010/index.html). The climate varies
specialization makes it vulnerable to extinction considerably with latitude. In the South it is warm
(Birdlife 2004). In Italy 350-400 breeding pairs temperature, with almost no rain in summer, while
are estimated (Birdlife 2004), but recent counts in the Northern part of the Peninsula temperature
at some migration hotspots have shown that their is cool with rainfall more evenly distributed
number is increasing (Baghino & Premuda 2007). throughout the year. The mean altitude in Italy is
Most of the breeding pairs in Italy are distributed 337 meters above sea level. According to Corine
in northern Italy and along the western slope of Land Cover 2000, in Italy we found 152.435 km²
central Italy (Campora & Cattaneo 2006). The of cultivated lands, 18.835 km² of permanent
Short-toed Snake Eagle is a broad-winged raptor pasture lands, 79.425 km² of woodlands, 22.555
with a high skill in the use of soaring-gliding km² of shrubs, 3.827 km² of wetlands and 14.340
flight since the energy consumption increases km² of urbanized areas. In lowlands agriculture is
disproportionately using powered flight; as a very intensive and devoted mainly to monoculture,
result this species tends to migrate over land and while on the hills and mountains traditional and
to avoid water crossing where thermal currents are less intensive agriculture is still practiced although
absent and it is forced to use active flight (Kerlinger land abandonment is spreading. Mainland Italy
1989). For this reason individuals belonging to may be divided into four major geographical
the Italian population migrate both during spring and vegetational areas: the Alps and the Padana
and autumn across the Strait of Gibraltar avoiding plain in the North, the Apenines and the coastal
the crossing of the Central Mediterranean flyway slopes (7.456 km of coastlines) in the centre and
that would imply a long water crossing (at least the south. The Alpine area is relatively unspoiled,
130 km) through the Channel of Sicily. Similarly with deciduous, mixed coniferous forests, alpine
individuals breeding in Greece migrate through pastures above the timberline, and snowfields
Turkey crossing the sea at Bosphorus (Agostini and glaciers on higher peaks. The Po valley is the
et al. 2002a, 2002b, 2004, Mellone et al. 2011, largest lowland area in Italy, mainly covered by
Panuccio et al. 2011). Since, as mentioned above, intensive agriculture. Large areas of the Apennine
the bulk of the breeding pairs of this species in mountains are still covered by semi-natural
Italy is located along its migration route, Agostini deciduous forests, mostly oak (Quercus), beech
and Mellone (2008) suggested that the Short-toed (Fagus) and sweet chestnut (Castanea), although
Snake Eagle is apparently still colonizing Italy large areas have been cleared for agriculture and
from the western part of its European breeding pasture. Coastal areas in Italy are dominated by
range and that, for this reason, its population has shrub and in particular by typical Mediterranean
not yet reached the carrying capacity. scrub. The protected earth areas in Italy cover a
In this paper we test this hypothesis considering surface of 13.000 km² (Brandmayr 2002).
several ecological (land use and prey richness), Sampling units:
topographic (altitude) and latitudinal parameters The geographical grid we used to divide the Italian
in order to find which ones affect the breeding peninsula in several sampling units is the same used
distribution of Short-toed Snake Eagle in Italy from IGM to draw the 1:25000 maps of Italy in
and to verify if some areas in Italy are not suitable UTM projections, overall we consider 3541 cells
for the presence of Short-toed Snake Eagle or have of 10x10 Km2. Because the Italian peninsula is
not been colonized or re-colonized yet.
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