The accession of Hungary to the European Union is likely to result in the intensification of arable crop cultivation. As a result of market forces and rural development measures, small parcels of land will be consolidated into larger fields. It is also likely that the area of maize and oilseed rape, and to a lesser extent that of sunflower, will increase at the expense of cereals. Abandoned land, ineligible for area payments will probably not return to cultivation. To identify the potential impact of these changes on the populations of common farmland birds, we analysed the data from 680 homogeneous sample plots of the Hungarian Common Bird Monitoring Scheme (MMM) from 2003. We used pair-wise comparisons with the Mann-Whitney test to identify the difference in the index of abundance of 34 species amongst the following categories of crops: abandoned versus cultivated arable land, small parcels versus large fields, cereals versus maize, sunflower and oilseed rape, fallow land versus small or large fields. Our results suggest that land consolidation will have the most serious negative impact on common farmland bird populations because small-scale farming systems hold significantly larger numbers of seven common farmland bird species, — White Stork Ciconia ciconia, Lapwing Vanellus vanellus, Wood Pigeon Columba palumbus, Whinchat Saxicola rubetra, Stonechat Saxicola torquatus, Tree Sparrow Passer montanus, Greenfinch Carduelis chloris, — than large-scale farms. On the other hand, the compulsory setaside might present some opportunities for the compensation of these negative effects if biodiversity considerations are integrated into the national rules, because fallow land held significantly higher densities of nine species, — Linnet Carduelis cannabina, White Stork, Yellowhammer Emberiza citrinella, Grasshopper Warbler Locustella naevia, Woodlark Lullula arborea, Whinchat, Stonechat, Whitethroat Sylvia communis and Blackbird Turdus merula, — than large crop fields. Comparison of large-scale cereal fields with large-scale maize, sunflower or oilseed rape fields, respectively, revealed significant differences only in the case of a few species, for example, the greater abundance of Skylarks Alauda arvensis in cereal than in maize, of Lapwings in sunflower and of Whinchat in oilseed rape than in cereal fields.