Population density and species composition changes for breeding bird species in farmland woodlots in western Poland between 1964 and 1994

Abstract

Intensive farming practices can impact on bird species richness and density. The paper analyses long-term changes in the breeding avifauna of small mid-field woodlots (avenues, shelterbelts and tree clumps) in intensively used farmland in Wielkopolska region (western Poland). It is the only set of data allowing the analysis of long-term trends in bird breeding in the Polish agricultural landscape. The estimation of population density was done with the mapping method in three periods: 1964–1966, 1984 and 1991–1994. Since 1960 farming systems in Wielkopolska have been strongly intensified: e.g. the yield of wheat ( Triticum sp.) have risen from 2 to 5 Mg ha −1 and the number of tractors per 100 ha from 0.5 to 8. The number of breeding species was found to have increased from 44 in the 1960s to 51 in the 1990s. Total density of breeding birds was lower only in woodlots where trees had been cut before 1990s, remaining unchanged in other woodlots (at 23–24 pairs ha −1). However, there has been a significant decrease in number of some ‘farmland specialists’ like Corn Bunting ( Miliaria calandra) and Ortolan Bunting ( Emberiza hortulana), while a slight increase occurred in the group of species linked with wood habitat. Although species number and population density of birds breeding in farmland woodlots have changed only slightly in the study area, the population trend analysis suggests that even moderately intensified agriculture (by EU standards) affects the community of birds.