Farmland birds are one of the most endangered European ornithological communities. Spain has a large farmland area that holds over 90% of the European populations of eight species included in EFBI (European Farmland Bird Index) (Butler et al, 2010). Agri-environmental measures in Spain face a major challenge of environmental conservation with impact beyond our borders. The aim of this work is to evaluate farmers' incentive to participate and to conduct a comparative analysis of agri-environmental measures aimed at the protection of farmland birds in the regions of Aragon, Castilla La Mancha, Castilla y Leon, Catalonia and Extremadua. The economic analysis of contract requirements shows the major opportunity costs. Finally, several recommendations arise in order to increase farmer participation and improving scope of agri-environmental measures.