Seasonal bird assemblages in Dehesas (substeppic prairies with Quercus suber) of North-Western Sardinia (Italy): A poorly studied landscape of high eco-biogeographic interest

Abstract

Dehesas (i.e., substeppic prairies with Quercus suber) represent a poorly studied Mediterranean habitat type of high eco-biogeographic interest. Here, we applied a point-transect method along a yearly cycle (from spring to autumn), to focus on seasonal differences in bird assemblages inhabiting a Dehesas landscape in north-western Sardinia (Italy). We confirmed the presence of Mediterranean species with restricted ranges (e.g. Sturnus unicolor, Sylvia sarda). At the community level, seasonal patterns show significant differences among mean abundance, with a maximum in autumn and a minimum in summer. The highest values in autumn may be explained by the aggregations of wintering small passerines. Considering the univariate metrics of diversity, the number of species significantly differs among seasons, with the richest community in spring. Shannon-Wiener diversity and Margalef (normalized richness) were higher in spring and summer compared to autumn. Habitat heterogeneity of these landscape mosaics, driven by historical agro-pastoral practices (fires and pastures), together with the presence of patchy 'key structures', positively affects bird species richness and abundance, improving, respectively, the number of niches and resources. More resource effort should be devoted to study these habitat types recently interested in an increased anthropogenic pressure (urban sprawl and road infrastructures, location of wind power plants, etc.).&nbsp