Effects of landscape composition on farmland and red-listed birds in boreal agricultural-forest mosaics Raimo Virkkala, Miska Luoto and Kalle Rainio Virkkala, R., Luoto, M. and Rainio, K. 2004. Effects of landscape composition on farmland and red-listed birds in boreal agricultural-forest mosaics. / Ecography 27: 273  /284. Farmland birds have declined in large areas of western and northern Europe. This decline has been connected with changes in the agricultural landscape. We studied the effects of landscape composition on birds in a boreal agricultural-forest mosaic in SW Finland. This study was carried out with a grid-based approach: bird pairs were counted in 105 grid squares of 25 ha within an area of 26.25 km 2 . The total density of farmland birds and density of red-listed species were related to the land cover variables using generalized linear modelling (GLM). Farmland birds consist of a variable group of species either breeding or feeding in agricultural land. The model explained a moderate proportion (49%) of the variation in the total density of farmland birds in the landscape. In a regression analysis coverof non-arable agricultural land (semi-natural grasslands, built-up areas) explained a much higher proportion (r 2 /0.49) of the variation in farmland bird density than that of arable land (cultivated fields and set- aside fields, r 2 /0.04). Semi-natural grasslands, which have drastically declined throughout NW Europe, and built-up areas (mainly farmyards) had the most significant positive effects on the density of red-listed species. The results emphasize the significance of semi-natural grasslands for the declining red-listed farmland bird species. Birds are usually not restricted to certain patches of habitat but use several patches in their home range. Thus, when studying bird-landscape relations for land use planning, we also recommend grid-based approaches covering the whole landscape variation. R. Virkkala (raimo.virkkala@ymparisto.fi) and M. Luoto, Finnish Environment Inst., Research Dept, Research Programme for Biodiversity, P. O. Box 140, FIN-00251 Helsinki, Finland.  / K. Rainio, Dept of Biology, Univ. of Turku, FIN-20014 Turku, Finland. Patterns of landscape composition, structure and dy- namics are highly influential in preserving and main- taining biodiversity. Changes in the composition and quality of habitats in a landscape affect species popula- tions. Habitat loss, degradation and fragmentation are by far the most important factors affecting the endan- germent of species (e.g. Anon. 1992). For example, /80% of all red-listed (threatened or near-threatened) species recorded in Finland (2565 species; vertebrates, invertebrates, plants, fungi) are primarily threatened by habitat changes (Rassi et al. 2001). In maintaining populations of species it is crucial to analyse landscape level factors affecting the habitat preferences and spatial distribution of threatened and decreasing species. Birds often use patches of several different habitat types within their home range. Therefore, studies dealing with bird-landscape relations should not cover only individual habitat patches. Compared to many other species groups (plants, insects), birds use landscape in a more coarse-grained manner (cf. Wiens 1989, Forman 1995 and references therein). Landscapes of agricultural-forest mosaics have chan- ged considerably in Finland (Pitka ¨nen and Tiainen 2001), as have agricultural landscapes in northwestern Accepted 26 January 2004 Copyright # ECOGRAPHY 2004 ISSN 0906-7590 ECOGRAPHY 27: 273  /284, 2004 ECOGRAPHY 27:3 (2004) 273