Population Consequences of Displacement from Proposed Offshore Wind Energy Developments for Seabirds Breeding at Scottish SPAs

Searle, K.; Mobbs, D.; Butler, A.; Bogdanova, M.; Freeman, S.; Wanless, S.; Daunt, F. (2014). Population Consequences of Displacement from Proposed Offshore Wind Energy Developments for Seabirds Breeding at Scottish SPAs. Report by Marine Scotland Science. Report for Marine Scotland Science.

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Abstract

The aim of this project was to develop a model to estimate the population consequences of displacement from proposed offshore wind energy developments for key species of seabirds breeding at SPAs in proximity to proposed Forth/Tay offshore wind farm developments.
The steering group identified five seabird species for which displacement modelling was required in support of HRA/AA for Forth/Tay developments: black-legged kittiwakes Rissa tridactyla; common guillemot Uria aalge; razorbill Alca torda; Atlantic puffin Fratercula arctica; northern gannet Morus bassanus.
The steering group agreed that the SPAs to be considered in this report were Buchan Ness to Collieston Coast SPA, Fowsheugh SPA, Forth Islands SPA and St Abb’s Head to Fastcastle SPA.  We considered impacts of displacement on population size operating via two main processes: reduced survival of offspring during the breeding season, and reduced body mass of adults leading to lower survival in the following winter.  Displacement effects are of two main types: the effects of displacement of birds that intended to forage in the wind farm, and the effects of the wind farm acting as a barrier to movement of birds intending to forage beyond the wind farm.
This study is, to our knowledge, the most comprehensive assessment of the population level consequences of displacement for seabirds to date. Displacement effects have been considered to potentially impact on chick survival. What has been less widely appreciated is that impacts on adult survival are also possible, mediated via changes in body condition. Declines in adult and chick survival were recorded for some species/wind farm/SPA combinations that matched expectations in terms of foraging range, foraging costs and wind farm location relative to SPAs. The model had to make a number of assumptions that would benefit from parameterisation with local data, in particular prey distribution, behaviour of seabirds in response to wind farms (including habituation) and effects of adult body mass change on subsequent survival.