Page 107 - Panuccio2012

Southbound direction of colonization of Short-toed Snake Eagle

Figure 3
The probability of occurrence of
Short-toed Snake Eagles in the
two different models with (a) and
without (b) latitude variable.

a

b

does not includes latitude among variables, shows potentially affect the distribution of the species
a wider potential distribution, also in southern in the breeding areas, forests and preys’ richness
Italy (Fig. 2). are the most relevant. In particular, this result was
Moreover plotting the probability of occurrence obtained using both models A and B such as the
of Short-toed Snake Eagles in the sample units Maxent model. Forests are important for Short-
in relation with latitude, the results clear change toed Snake Eagles because they nest on trees and
for the two models, showing a more homogenous this is in agreement with most of previous research
distribution in the case of Model B (Fig. 3). (Sánchez-Zapata & Calvo 1999, Bakaloudis et al.
Finally the results showed by Maxent analysis (Fig. 2005, Bustamante & Seoane 2004, Lopez-Iborra
4) confirm the potential distribution predicted by et al 2010). Anyway as showed by the high Wald
Model B. In particular the variables that give the value of the variable “square root forest” (Tab.
higher contribution in the Maxent model is the 3) the extension of forests is important for the
Corine Land Cover (63,5%) followed by slope presence of Short-toed Snake Eagles but there is
(27,7), while elevation (5,4%) and aspect (3,4%) a threshold value beyond which the overgrowth of
are less important. Land Cover categories included forests becomes a limit for this species; and this is
in the model are (in order of weight): Mixed reasonable since snake eagles hunt in open areas.
Forest, Transitional Woodland Scrub and Broad- Prey richness is the other variable that explains
leaved Forest. AUC of this model is 0,914. eagle distribution. A previous investigation in
DISCUSSION Short-toed Snake Eagle made in southern Spain
This study shows that among variables that highlighted the relationship between the presence
of the eagles and species richness of reptiles (Moren-

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