As a result of intensified agriculture, farmland in Europe is the habitat where the most pronounced changes have occurred in recent decades. In parallel, breeding populations of birds have been declining over much of Europe. Today, farmland has the largest proportion of Red-List species. This paper reviews studies on the impact of agriculture on birds breeding in the farmland ecosystems of Europe: breeding bird density in relation to farming practice, effects of agriculture on foraging and feeding ecology while rearing young, and consequences for breeding success.
Specialised bird species are most affected by farming practice. They are rare or even absent in intensively managed farmland with a much reduced habitat and structural diversity. As crops grow fast and as their vegetation is very dense, large fields become inaccessible to or unprofitable for ground feeding birds. To exploit alternative food resources, parents feeding nestlings have to cover larger distances to isolated and distant food patches. Reduced food availability in modern farmland and increased time and energy costs of foraging may result in lower body conditions of parent birds and their broods, in a reduced breeding success and lower survival. Some species breeding in intensively farmed areas are at least locally unable to produce sufficient recruits to maintain their numbers in the long term.
Our knowledge of the breeding ecology and population dynamics of farmland birds is growing, but it is still based mainly on short-term and small-scale case studies on a few species. Little is known about whether measures to improve habitat quality (e.g. set-asides) are adequate to halt negative trends in bird populations. Hence, there is a need for internationally coordinated scientific work with important implications for conservation.