Consideration of avoidance behaviour of northern gannet (Morus bassanus) in collision risk modelling for offshore wind farm impact assessments.

Published online
19 Oct 2023
Published by
Natural England
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Pavat, D. & Harker, A. J. & Humphries, G. & Keogan, K. & Webb, A. & Macleod, K.
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The aim of this project was to deliver an evidence-based method to ensure macro-avoidance behaviour is appropriately accounted for in collision risk models of gannets (Morus bassanus) at offshore wind farms (OWFs). The literature review identified that the two types of macro-avoidance (barrier effects and displacement) could not be disentangled from existing studies. In the available literature for gannet, nine studies report macro-avoidance rates for at least ten OWFs that could be used in collision risk modelling. These values ranged from 0.617 to 1.000 and were determined using a mixture of survey methodologies (e.g., horizontal and/or vertical radar, GPS tagging studies, visual, boat-based, aerial surveys and before/after comparisons of densities), and for several very different wind farm sites. It was concluded that a macro-avoidance rate for gannet should be calculated based on a simple mean approach. Nevertheless, the role of individual-based models needs to be fully investigated as an alternative for deriving macro-avoidance rates. To incorporate macro-avoidance into collision risk modelling, it was recommended that the input densities are corrected by the pre-determined or calculated macroavoidance rates, and a 'within wind farm' avoidance rate is then applied in the collision risk model. This would involve very little effort in terms of the tools currently available (e.g., stochastic collision risk model). In this way, temporal effects (i.e., differences in macro-avoidance throughout a year) could be incorporated as well.

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