Zur Bedeutung von Kleinstrukturen im Ackerland: Bevorzugt die Feldlerche (Alauda arvensis) Störstellen mit Kümmerwuchs?

Summary: Micro-structures in arable fields are apparently of great importance for the Skylark, a species which has declined over vast areas of Europe. In two study areas (U1, U2) in SW-Germany, in early summer the Skylark showed a preference for arable fields with low emergent crops, with 88% (58%) of the territories on 35% (33%) of the total area of U1 (U2), and with 3.0–3.8 (4.1–4.3) territories per 10 ha. The distribution of Skylark territories showed a strong preference for "places with stunted growth" caused by traditional cultivation practices (clumping of abrupt changes in the direction of the edges of plots, shallow depressions along the longer margins of plots with elevated central parts, i.e. furrow and ridge), or by microtopographical-geological conditions (doline over karst, wet or stony places); and a marked avoidance of arbitrary places anywhere in the fields; on the other hand, places with stunted growth caused by modern cultivation (edges of stands, clay- or grass-covered country-lanes) were used less frequently than expected (Fig. 1). The preferred places with stunted growth often originated around edges of plots in traditional small-scale cultivation, but are nowadays mostly situated within actual stands, the former edges having been tilled over. With respect to conservation, preferred places like these should be evenly dispersed over the arable fields, thus building up a mosaic of micro-structures. [ABSTRACT FROM AUTHOR]