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Southbound direction of colonization of Short-toed Snake Eagle
Figure 4 – Distribution map of suitability through a top-down process (Moren-Rueda &
according to Maxent. Pizzarro 2007). On the other hand, differently
Rueda & Pizzarro 2007). Despite the high trophic from previous research, in our model shrubland
specialization, the Short-toed Snake Eagle behaves doesn’t result as an important variable. This maybe
as a taxonomical generalist within this prey type, because we considered only breeding data of Short-
and only selects optimal prey sizes whatever is toed Snake Eagles while other authors considered
the species (Gil & Pleguezelos 2000). So why is also observations of hunting individuals (Lopez-
there a correlation between prey species richness Iborra et al 2010). In fact areas with a high diversity
and eagles distribution? Different explanations of shrublands may be important for eagles as they
were proposed to read this correlation. Among may create edges between different habitat types,
them, the possibility that the abundance of reptile which may be related to a high abundance of prey
individuals correlates with reptile species richness (Moren-Rueda & Pizzarro 2007, Wisler et al.
and the abundance of individuals determines the 2008, Lopez-Iborra et al 2010).
presence of raptors (Evans et al 2005, Moren- In our first Model (A) also the latitude had a
Rueda and Pizzarro 2007). Another possibility is significant effect on the distribution of Short-toed
that, species of reptiles show different temporal and Snake Eagles breeding in Italy. In particular its
spatial patterns and this fact could have favored effect is the opposite of the one revealed in Spain
the hunting chance for eagles. Also intra and inter (Lopez-Ibozza et al. 2010), where the latitudinal
specific interactions due to different prey selection increase has a negative effect on the distribution
were suggested. Finally it was hypothesized that of the species. We found, on the contrary, that in
the presence of Short-toed Snake Eagle favors Italy the presence of the species seems to increase
more reptile species richness through a control with the latitude. However, the distribution of
on the most abundant population species that the Short-toed Snake Eagle in Europe does not
could reduce competition intensity among reptiles lead to the conclusion that latitude could have
the effect showed in the model A. In fact, this
eagle is widely distributed in southern Europe
at the same latitude of southern Italy in Spain,
Greece and Turkey (Handrinos & Akriotis 1997;
Mañosa 2003, Kirwan et al. 2008). In addition,
our models B and Maxent model clearly show that
large areas, especially in the southernmost part of
the peninsula, are suitable for this species although
the known distribution, showed by data available
for Italy, is well represented by the map obtained
with the Model A. Perhaps, the distribution of
the Short-toed Eagle in Italy, unexpected when
considering both model B and Maxent, could be
the result of the interaction of variables not related
to the latitude and species’ breeding ecology but
linked to the geography of the Italian Peninsula
and the ecology of Short-toed Snake Eagle
migration. In fact, as mentioned above, the Central
Mediterranean is an ecological barrier for this
species, since Short-toed Snake Eagles avoid the
crossing of large bodies of water during migration
using mostly soaring-gliding flight over land as a
result of a conservative strategy (see Agostini et
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