Investigating avoidance and attraction responses in lesser black-backed gulls Larus fuscus to offshore wind farms

Abstract

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.

A new method for quantifying redistribution of seabirds within operational offshore wind farms finds no evidence of within-wind farm displacement

“…10 km (Mendel et al, 2019;Vilela et al, 2021;Garthe et al, 2023), while other species, such as large gulls (Larus sp. ), appear to show either no response or attraction to turbines (Welcker and Nehls, 2016;Johnston et al, 2022) and cormorants (Phalacrocorax carbo) are regularly reported to be attracted to turbines, or more pertinently to the structures and the opportunities for roosting provided (Canning et al, 2013;Leopold et al, 2013). Contrary to the results of this study, guillemot and razorbill have most often been reported to show intermediate levels of displacement/avoidance (e.g.…”

A framework for studying the effects of offshore wind energy development on birds and bats in the Eastern United States

“…There has been very limited empirical validation of CRMs, and terrestrial studies of raptors in Spain found low correlation between actual collisions and predicted collision risk from CRMs (De Lucas et al, 2008). The models are particularly sensitive to avoidance rates; avoidance can occur at multiple spatial and temporal scales and is difficult to measure quantitatively, though advances in technology, such as GPS and the abovementioned combined radar/camera systems, are providing new insights (Johnston et al, 2022;Tjørnløv et al, 2023). Recognizing the potential variation in many CRM input parameters, there have been efforts to develop stochastic models to better reflect uncertainty and incorporate spatiotemporal variation (McGregor et al, 2018).…”

Flight heights obtained from GPS versus altimeters influence estimates of collision risk with offshore wind turbines in Lesser Black-backed Gulls Larus fuscus

“…Turbine blades are a potential collision risk to seabirds; estimating the number of collision mortalities that might result from the development of a wind farm is an important aspect of Environmental Impact Assessments (EIAs). The extent of collision risk posed by wind farms to seabirds is dependent on several factors including: the flight heights exhibited by birds in relation to the rotor swept area of a turbine [ 3 ]; their flight speeds [ 4 ]; and avoidance behaviour undertaken in relation to individual turbines [ 5 , 6 ], or entire wind farms [ 7 – 9 ].…”

“…Tracking data have also shown how birds adjust their flight heights in response to turbine rotor swept areas [ 5 , 25 ]. Therefore, bird-borne telemetry can be routinely applied to examine: seabird area use in the offshore wind farm consenting process; responses to offshore wind farms following consent and construction [ 7 , 26 ]; and detect direct interactions with turbines [ 5 , 9 ]. The impacts of collision on seabird populations arising from offshore wind farms are usually assessed in EIAs through Collision Risk Models (CRMs) such as the Band model, a mechanistic model which estimates the number of collisions with a wind farm based on the likelihood of a bird colliding with a turbine blade while flying through the rotor swept zone (RSZ), and the number of birds potentially occupying the RSZ at any given time within the wind farm [ 27 , 28 ].…”