Many studies have shown how intensification of farming is the main cause of loss biodiversity in these environments. During the last decades, agroecosystems in Europe have changed drastically, mainly due to mechanization of agriculture. In this work, species richness in bird communities was examined on a gradient of spatial heterogeneity of farmlands, in order to quantify its effects. Four categories of farmland spatial heterogeneity were defined, based on landscape and landuse parameters. The impact of features increasing the spatial heterogeneity was quantified comparing the similarity indexes between bird communities in several farmlands of Central Italy. The effects of environmental variables on bird richness were analyzed using GLM. The results highlighted that landscape features surrogates of high nature values (HNVs) of farmlands can increase more than 50% the bird species richness. The features more related to bird richness were hedgerows, scattered shrubs, uncultivated patches, and powerlines. The results confirm that the approach based on HNV for evaluating the farmlands is also suitable in order to study birds’ diversity. However, some species are more sensitive to heterogeneity, while other species occupy mainly homogeneous farmlands. As a consequence, different conservation methods must be considered for each farmland bird species. 1. Introduction Agricultural intensification is one of the main drivers of biodiversity decline. During the last twenty-five years a rapid and large scale change of the agricultural landscape occurred in Europe, caused by the intensification and mechanization of agricultural activities [1, 2], and for this reason understanding the relations between biodiversity and land-use intensity is quite important to developed effective plans for habitat conservation [3]. Many studies about biodiversity in agroecosystems usually faced the problem that both management type and landscapes features can affect it [4–6], but a quantification of the real impact of each of these factors on the composition of animal communities is complicated. Biodiversity in farmlands is affected by land-use management at a small spatial scale (grazing intensity or crop rotation) and also at a large spatial scale [3]. All of this is related to the presence and/or distribution of landscape features that may reflect a low fragmentation of the habitat, which is often called “functional heterogeneity,” and is very important in supporting biodiversity [7–11]. Many studies have shown that organic systems may enhance bird species diversity over nonorganic
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