Bruderer, B. & F. Liechti
(* = Kurzbeitrag)
Welcher Anteil ziehender Vögel fliegt im Höhenbereich von Windturbinen?
(von 1994 bis 2006 vergeben)
Bird migration, height distribution, flight altitude, wind turbine, collision, radar
Vogelzug, Nachtzug, Tagzug, Höhenverteilung, Zughöhe, Zugdichte, Leitlinien, Windkraftanlage, Kollision, Radar
Neerach, Zürich, Römerswil, Sempach, Luzern, Mittelland, Jura, Alpen, Schweiz, Stuttgart, Baden-Württemberg, Deutschland
What proportion of migrating birds flies in the height zone of wind turbines? This report provides information on the height distribution of bird migration in an inland area of Europe, meant for the application in environmental impact studies on wind turbines, but without discussing the applied aspects directly. A brief introduction on methodological preconditions for radar studies in this field aims at preventing oversimplified approaches with inappropriate equipment. Three examples of lowland stations in relatively flat areas of Switzerland and southern Germany provide typical height distributions of nocturnal migration with an average of 15–25 % of birds below 200 m a.g.l. (above ground level). Data on diurnal migration are less reliable due to birds flying in flocks, low number of echoes, and many diurnal migrants flying below 30 m a.g.l. in opposing winds, and thus below the reach of the radar. The recorded mean distributions show 38–53 % of the echoes below 200 m a.g.l., standard deviations reaching up to 65 %. In opposing winds, even more birds may fly in this lowest height zone. Horizontal concentrations of birds have to be expected along topographical structures crossing their intended migratory direction at a narrow angle. Steep valleys and passes induce additional vertical concentrations. For autumn migration in the western parts of central Europe such leading lines consist mainly of WSW-leading mountain ridges, valleys and passes. In spring, the western parts of the Alps and the Jura would lead to a slight northward shift of migrants approaching from SW, but would not induce important concentrations, except some local funnelling induced by north- or northeastwards leading Alpine valleys.
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