The paper deals with the population changes of birds inhabiting an extensive area (15.8 km2) dominated by arable land, situated on the Silesia Lowland in south-western Poland. The number of territories was established with the use of the mapping method in the years 1977-1979 and 2001. Some changes in habitat and indices of agricultural production occurred between the two study periods. The 2001 study revealed a clear rise of the species diversity and the area was colonised with 18 new bird species. In the group of agricultural birds the only visible decrease was recorded for the species nesting in or using open cultivated areas, where the total abundance dropped. Within this group the most affected were: Perdix perdix, Vanellus vanellus and Alauda arvensis. The abundance of species inhabiting non-cropped, treeless habitats within open farmland went up. The total abundance of twelve species nesting in hedgerows and woodlots also rose. The severe reduction of the bird populations inhabiting open farmland is most probably associated with much larger environmental changes linked with intensification of agriculture, compared to the small transformations of the non-cropped or marginal habitats (sometimes becoming even larger and more diverse), where bird abundance went up.
1. The Heteroptera, principally mirids, collected in a light-trap run on a field margin at Rothamsted Experimental Station for various periods between 1933 and 2000, have been identified, and the catches analysed to show the extent of change and stability in the community.
2. Trap catch, both in terms of individuals and species, was correlated with maximum daily temperature.
3. α-diversity showed a U-shaped curve over the period. The dip may have been associated with pesticide use, although a lack of days with high maximum temperatures cannot be ruled out.
4. By the late 1990s, α-diversity had again reached a peak (Fisher's = 11), comparable to that in the 1930s.
5. However, the change in the composition of the community over the whole period (β-diversity) was significant, the index of difference being 0.66 on a scale where 0 is no change in composition or relative abundance and 1 no species in common.
6. The value of β-diversity was highest in the water bugs, which disappeared altogether. Categorising the others by host plant type, the greatest change over time was in those associated with perennial herbs. There were decreasing differences in tree-dwellers and grassland species respectively, and the least change was in the community associated with annual plants (arable weeds).
7. Changes in the abundance of Heteroptera since 1933 follow closely those of the macrolepidoptera from the same samples. However changes in diversity show very different patterns, with moth diversity continuing to decline since 1960 in contrast to the increases apparent from the Heteroptera data.