The advent of set-aside may be the main reason why the cirl bunting, one of the country's most endangered species, has halted its decline.
The European Union policy of taking agricultural land out of production began on a voluntary basis in the late Eighties, when there were only 120 pairs left in Britain. Now there are more than 350.
The controversial policy exists to cut Europe's chronic over-production of cereals, but wildlife conservationists always hoped it could be used to repair some of the damage done by decades of intensive farming. One-eighth of Britain's cereal land is being set aside this year.
Dr Andy Evans, an RSPB researcher, told a farmland birds conference in Thetford, Suffolk, that the idle farmland was a rich source of winter food for several species. They relied on grain spilt into the fields at harvest time and the seeds of weed plants.
But the advent of autumn-sown cereal crops in recent decades had removed the stubble fields. Along with the loss of mixed farming - pasture and cropland - this has drastically reduced the populations of linnet, tree sparrow, grey partridge and turtle dove, as well as the two types of bunting and skylark.
The RSPB researchers have studied dozens of set-aside fields in Devon and East Anglia over the past three winters, comparing how often birds feed on these compared with conventional cereal fields; nearly twice as many bird species were found on set-asidefields, and on average they contained 15 times the total number of birds.Reuse content