ABUNDANCE OF BREEDING FARMLAND BIRDS ON ARABLE AND SET-ASIDE FIELDS AT FOREST EDGES

The aim with this study was to investigate whether abundance of farmla nd birds on fields at forest edges were associated with (i) type of fi eld (young set-aside vs arable fields), (ii) the length and structure of the field-forest edge zone, and/or (iii) with residual habitats suc h as habitat islands, ditches, roads etc. Twenty-eight farmland bird s pecies (all nesting and/or foraging on open fields) were censused duri ng the breeding season on 48 plots (open fields with adjoining forest edges) in the central parts of Sweden, covering a total area of 595 ha . Skylark Alauda arvensis, linnet Carduelis cannabina, whitethroat Syl via communis and whinchat Saxicola rubetra were found in significantly higher numbers in set-aside-plots than cereal ones. However, the most important factor explaining variation in the abundance of most specie s was the structure of the field-forest ecotone, with the length of sh rubby southern deciduous forest edges being the most important factor in 7 of the species. Mixed forest edges seemed to be of some importanc e for the abundance of 3 species, while associations between abundance and length of the other deciduous and coniferous field-forest ecotone s only were significant for one species each. Skylarks, white wagtails Motacilla alba and whinchats were positively associated to ditches an d yellowhammers Emberiza citrinella and linnets were significantly ass ociated to habitat islands. The observed preferences for set-asides an d shrubby field forest edges are suggested to be results of reduced pr edation risk and increased food abundance.