Editors' introduction: birds and agriculture.
This paper introduces a special section of this journal issue on birtds and agriculture, which comprises 7 further papers. Around 10% of recent papers in the Journal of Applied Ecology have examined interactions between birds and agriculture. Papers in this Special Profile illustrate how research in this sphere has shifted towards assessing the processes by which birds are affected ecologically by agricultural change. The works examine spatial patterns in extinction; assess long-term trends in bird abundance and agricultural practice; reveal how foraging and breeding performance in farmland birds varies between habitats; and evaluate the role of large-scale modelling in examining hypotheses about the influences of land management on birds. The final paper shows that birds can have intrinsically positive value in agricultural systems. All the papers propose management prescriptions for agricultural areas that blend the microscopic - for example, how to modify local land structure to benefit birds - and the macroscopic - for example, by suggested inputs into land-use policy. Perhaps most pertinent is the key conclusion that agricultural change is multivariate, so that straightforward univariate effects on birds are unlikely. Restoration of impacted populations might therefore require holistic strategies that encourage appropriately scaled agricultural extensification. Success would be most likely if farmers, conservationists and other key players were engaged collaboratively in the process. Current ideas about restoring farmland bird populations share a common assumption: if agricultural practice has reduced populations hitherto, then agricultural practice can restore the losses. We suggest that this assumption carries a range of predictions that now require testing through sustainable farm management - a situation ideally suited to 'BACI' style experiments. We reiterate the need to expand work on other groups of organisms affected negatively or positively by agricultural management to allow a broader perspective of impacts or benefits.