Telemetric Monitoring of Montagu’s Harrier in Schleswig-Holstein

Abstract

The behaviour of breeding Montagu’s harriers towards wind farms in Schleswig-Holstein in Northern Germany was investigated in a two years telemetry study. A total of 11 breeding birds were fitted with VHF transmitters. The home ranges varied between 340 and 1560 ha (kernel). Males had larger home ranges than females. Centres of flight activity (50% kernel) were in the surroundings of nests and comprised between 41 and 252 ha. The salt marshes of the intertidal zone and large extensive grasslands rich in ecotones were important foraging grounds. Wind farms within the home range were used without avoidance of the close-up area of wind turbines. The intensity of use depended on location and distance of wind turbines from the centre of activity (nest) and available foraging grounds. The results gave no hint of displacement effects in the selection of the nest site or avoidance behaviour in the use of the habitat. 60–70% of the flight heights of Montagu’s harriers were below 10 m, rarely reaching the risk area of currently installed wind turbines. Flight activities in critical heights were concentrated on the nest site with 50% of the recorded locations within a radius of 182–497 m around the nest. With increasing distance from the nest, the flight activity per area was decreasing considerably. Due to hunting flights, mainly below 10 m height, low collision risk occured in the periphery of the home range. The distance between nest and wind turbine was a decisive factor for the collision risk. Habitat management concepts in order to lower the collision risk by relocating breeding sites to locations outside the impact range of wind turbines and by channeling flight activity along suitable created foraging grounds are discussed.