Birds as useful indicators of high nature value (HNV) farmland in central Italy

Birds are commonly cited as an example of declining farmland biodiversity in Europe, especially in the economically and agriculturally developed countries of Western Europe. However, even in extensive farmland there are still patches of rich biodiversity, including of birds. These areas are known as high nature value (HNV) farmland. In these circumstances, more effort is needed to understand the importance of the spatial heterogeneity and dynamics of residual natural habitat for farmland birds, including the various links between land use and marginal vegetation structure and bird communities and the occurrence of individual species. In this study we use species distribution models (SDMs) in order to explore the importance of these patches for birds and examine the relationship between bird species richness and land use, landscape and vegetation type characteristics at a local scale in traditional farmland in Central Italy. Our results show that some forest related passerines and shrubland bird species are well represented in these farmlands. The HNV farmlands in Central Italy can also be studied using bird species as bioindicators. In our particular case, HNV farmlands were well predicted by the joint presence of four species and the absence of two bird species. Traditional farmland is therefore a valuable habitat and not ‘just’ a soft matrix for these birds. Moreover, complex models were better supported by the data than simpler models for all passerines. Modern agricultural techniques which simplify the structural complexity of farmland are likely to exclude many passerine species. Thus incentives to maintain small scale heterogeneity in traditionally managed farmland will be critical for maintaining their rich passerine bird communities.