Fallow management increases habitat suitability for endangered steppe bird species through changes in vegetation structure.
Abstract
In the face of the dramatic worldwide decline of farmland bird populations, the preservation of fallow fields is a conservation measure encouraged through subsidies (e.g. agri-environmental schemes, AES). Beyond the general benefits of increasing fallow availability for endangered steppe bird populations, there is a lack of knowledge on how fallow management can contribute to meeting species-specific habitat requirements. We used occurrence data from three steppe bird species protected at the EU level (Stone Curlew Burhinus oedicnemus, Little Bustard Tetrax tetrax and Calandra Lark Melanocorypha calandra), framed in a quasi-experimental approach covering an unprecedented spatio-temporal scale that included 612 fallow fields over a 3-year study period in an agricultural Mediterranean landscape (Spain). We used path analysis to explore the mechanisms by which common agricultural practices affected species-specific occurrence. We examined partial effects of agricultural practices on vegetation structure and food availability, and the partial effect of these variables on bird occurrence compared to control fields (no agricultural practices applied). Agricultural practices had a significant effect on the presence of the three studied species. Through changes in the vegetation structure, Shredding + Herbicide and Tillage increased the occurrence of the Stone Curlew and Shredding increased the occurrence of the Little Bustard. The occurrence of Calandra Lark was mostly affected by landscape variables. Synthesis and applications: Our study highlights that, in addition to the acknowledged positive role of fallow availability, applying a limited number of specific agricultural practices before the breeding season can further increase bird occurrence by changing the vegetation structure. Using path analysis, we explored the mechanisms driving the occurrence of three steppe bird species under different agricultural practices. Such information is key to providing specific recommendations for future conservation management of endangered species within agri-environmental schemes.