Multi-scalar analysis of bird communities in Monferrato Astigiano woodlands

In this study we focused on deciduous managed forests in north-western Italy and investigated relationships between bird diversity and forest descriptors both at the habitat and landscape level through a seasonal, guild-based approach. Birds were censused by point counts in randomly selected plots of 50 m radius. Each census plot was described in habitat structure terms by using the Bitterlich variable plot-radius method. Landscape metrics were measured within 250, 500 and 1000 m radius circles of each plot using an existing GIS database. We first identified specialist and generalist species according to the presence/absence of each species in relation to habitat structure measurements, then we tested for the effects of habitat and landscape variables on community and guild parameters (bird species richness, abundance and Shannon diversity) using generalized linear models (GLMs). Our analyses showed that in general, guild parameters relative to specialists were especially influenced by oak biomass and oak core area irrespective of the season, while parameters of generalists were influenced by oak core area in winter and by landscape fragmentation parameters in spring. Results clearly showed that the retention of native oaks both at the habitat and landscape level is the key-factor for the conservation of diversity of specialist bird species in deciduous, originally oak-dominated woods.