Effects of unsown patches in autumn-sown fields on Skylark territory densities : a study on skylark plots made in central Sweden

Abstract: Intensified cultivation of farmland is widely recognized to act negatively on many organisms, including birds as the Skylark (Alauda arvensis). During the last decades, this species has been showing a population decline of about 50-75 percent in northwestern Europe, including Sweden. One important factor that is considered to be a key driver of this decline is the switch from spring- to autumn-sowing of cereals. This change in farming practice has been shown to reduce food availability for skylarks and other species that rely on crop fields for foraging and nesting. To improve this situation, skylark plots (SPs), i.e. small (16-20 m2) unsown patches within winter cereal crops, have been developed in Great Britain during the last decade. The idea with SPs is to make it easier for skylarks to forage, since the sparser vegetation in SPs makes it easier to find food (i.e. invertebrates). From Great Britain the method has been shown to work well, increasing the breeding success of skylarks. However, the extent by which SPs contribute to improve breeding opportunities in Swedish arable farmland is unknown. There are structural differences in the agricultural landscapes of Sweden and Great Britain, with a higher relative proportion of spring sown cereals in Sweden. This might indicate that SPs have a lower positive effect when applied in Sweden, since the high proportion of spring cereals (sparser vegetation) makes it possible for skylarks to find food anyway. Thus it is important to study if SPs have a positive effect on skylarks in Sweden, before applying the method in a huge scale.