Mag. Barbara Lukasch

Short-term effects of recent land use changes in Eastern Austria on bird assemblages in a human-dominated landscape

To study effects of short-term land-use changes on birds in a predominantly agriculturally used landscape in Northeastern Austria, birds were surveyed in 22 circular study areas with a diameter of 1 km in 2005 and 2009. Also the proportion of landscape elements like set-aside land, cropland and woodland were measured in both years. Because of the abolition to obligate set-aside land in 2008 and 2009, it was suspected that the amount of set-aside land would be reduced dramatically. Consequently, a loss of biodiversity was expected, particularly in farmland bird species. Results show that the amount of set-aside land indeed decreased significantly between 2005 and 2009 from 15.05% to 9.69% (mean proportion of fallows per study area). However, total numbers of recorded species were very similar in 2005 (85 species) and 2009 (87 species) and in both years farmland birds were represented by 20 species.

The completeness of the totals species inventories was 90.36% and 96% in 2005 and 2009, respectively. Abundances of species in 2005 and 2009 were highly correlated, independently if all bird species or only farmland birds were considered. Based on the comparison of absolute abundances, no difference in the proportion of increasing and decreasing species was found between farmland and other bird species. To account for a potential observer-related bias, also relative abundances were considered. However, again no significant difference in the proportion of increasing and decreasing species was found between farmland and other birds. The relative abundances of 29 bird species increased (including 9 farmland bird species), and the relative abundances of 29 bird species declined (including 7 farmland bird species).

However, only two bird species showed a significant change between 2005 and 2009 (both farmland birds): Yellowhammer (Emberiza citrinella) increased and Common Kestrel (Falco tinnunculus) decreased. Species richness (all birds and farmland birds) was positively related to habitat diversity, while an increasing amount of 3 cropland had negative effects. Although a significant decline of set-aside land was recorded, no related significant changes of the bird assamblages could be detected.

However, the amount of set-aside land in these landscapes was already high (compared to other areas in Austria) before the amendment of the law and still relatively high after the abolition of the measures intending to maintain a high proportion of fallow areas. Therefore, perhaps the minor changes in the extent of set-aside land were below the threshold to find detectable effects on bird assemblages in strongly human-modified landscapes.