Two study areas, 210 ha (A) and 120 ha (B), have been selected. Arable grounds dominated (92%) in the study area A, while meadows (63% in 1989 and 47% in 2003) – in the study area B. The changes in land use in both study areas have occurred in 2003 comparatively with 1989. In the study area A, an increase of the area with maize (from 1.1 ha to 38.4 ha) and oat (from 5.6 to 28.4 ha), and decrease in area of the rape (from 41.3 to 0.3 ha) and root plants (from 16.7 to 6.4 ha) have been recorded, while the clover and broad bean have totally disappeared as cultivated plants. In the study area B, a conversion of some dry meadows into arable grounds and an abandonment of more than half of the remaining area of meadows has been carried out. The landscape in the study area A was more fragmented in 1989 than in 2003, while in the study area B the reverse was true. On average, cereal areas increased – especially wheat (from 1.5 to 2.4 ha), maize (from 0.6 to 3.8 ha) and oat (from 0.6 to 1.9 ha), while rape areas decreased (from 2.0 to 0.3 ha). The mapping method has been employed to show the effect of these changes on breeding bird community in both years (1989 vs. 2003). In the study area A, density (pairs × 100⁻¹ ha) of the Skylark Alauda arvensis (28.1 vs. 17.1) and Marsh Warbler Acrocephalus palustris (12.9 vs. 2.4) has significantly decreased; while that of Corn Bunting Miliaria calandra (1.4 vs. 8.1) and gallinaceous birds (2.9 vs. 8.1) has significantly increased over the last 14 years. The most numerous species in the group of gallinaceous birds, the Common Quail Coturnix coturnix, probably benefits from the enlargement of oat and barley cultivations. The Skylark was negatively affected by the enlargement of study areas with cultivated plants, especially with the wheat and maize. The Corn Bunting has been, probably, positively affected by the enlargement of maize and barley cultivations, as well as from the warming effect. The decline of the Marsh Warbler could have been caused by the decrease of the area with rape cultivations but it may also reflect short-term fluctuations. In the study area B, only densities of the Chaffinch Fringilla coelebs and Blackbird Turdus merula have significantly increased, and no statistically significant declines were recorded. These increases can be linked to changes in the age structure of tree and shrub stands in the existing small forests, clumps and hedgerows, but these species show probably a general increase in numbers over large areas of farmlands in Poland and possibly in some other European countries.
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