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Movements through or use of offshore wind farms by seabirds while commuting or foraging may increase the potential for collision with turbine blades. Collision risk models provide a method for estimating potential impacts of wind farms on seabird populations, but are sensitive to input parameters, including avoidance rates (ARs). Refining understanding of avoidance through the use of high-resolution empirical movement data has the potential to inform assessments of the collision impacts of offshore wind farms on seabird populations. We assessed the movements of GPS-tagged lesser black-backed gulls Larus fuscus from a breeding colony in northwest England to estimate the species’ AR and avoidance/attraction index (AAI) to nearby offshore wind farms. To investigate both macro- (0-4 km) and meso-scale (0-200 m) responses to wind turbines, we used calculations of AR and AAI based on simulated vs. observed tracks. We found that birds exhibited an AR of -0.15 (95% CI: -0.44 to 0.06), indicating a degree of attraction within 4 km of the wind farms. However, AAI values varied with distance from wind farm boundaries, with a degree of avoidance displayed between 3 and 4 km, which weakened as distance bands approach wind farm boundaries. Meso-scale avoidance/attraction was assessed with regard to the nearest individual turbine, and flight height relative to the rotor height range (RHR) of the nearest turbine. We found attraction increased below the RHR at distances <70 m, while avoidance increased within the RHR at distances approaching the turbine. We explore how high-resolution tracking data can be used to improve our knowledge of L. fuscus avoidance/attraction behaviour to established wind farms, and so inform assessments of collision impacts.

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SynopsisBracken is not a major weed problem on hill land in the north of Scotland, being restricted by environmental factors to the lower slopes of sheltered glens. There is no evidence of widespread stock poisoning by bracken in the area.Ploughing and reclamation, forestry planting and spraying with the selective herbicide asulam have considerably reduced infestations of bracken on land worthy of improvement. At the present time there is little scope for further economic control of bracken.Field experiments have defined full frond emergence from mid July to mid August as the most effective time for application of asulam. Reinfestation in about five years has been shown to follow incomplete control on small plots but an area sprayed by helicopter in 1972, where a very high degree of initial control was achieved, remained almost free of bracken in 1980.Easier handling of stock and increased availability of summer grazing are reported following bracken control. An increase in herbage production has been measured experimentally in the second year after removal of the bracken by spraying.

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