Mean range size of the species, bird richness and ecogeographical factors: data from Italian Peninsula and Islands

Battisti C. & Contoli L.

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slands are, generally, inhabited by widespread and generalist bird species. This phenomenon, well known in literature and here extended to a peninsular gradient, is confirmed in Italy for breeding landbirds, and for the sedentary ones, elaborating data of the Atlases. The mean range size values of the species are higher in all the studied islands compared to the mainland. The lesser the island area the higher is the mean range size of the species found. Stenotopic species, rare and localised, are present with lower frequency in small islands, the contrary occurs for widespread species. Along the Italian peninsula a high inverse correlation between mean range of distribution of the species and a number of variables of the latitudinal transects (number of species, highest altitude, area, latitude) has been found. This may be explained, mainly, by the different orophysiographical and environmental availability which affect, at the same time, the bird richness and, in particular, the distribution of the rare and localised species.