Offshore renewable developments (ORDs) have the potential to affect seabirds, through displacement from important at-sea foraging habitat. The UK Joint SNCB Interim Displacement Advice Note provides advice on how to present assessment information on the extent and potential consequences of seabird displacement from ORDs. According to this, assessments should use two metrics, displacement rate and displacement mortality rate to compile a ‘Matrix Approach’ table. The estimation of displacement mortality rates is a critical component of the assessment process for estimating impacts on seabirds arising from ORDs, with large influence upon resulting predicted ORD impacts for affected populations.

In this project we critically reviewed the displacement mortality rates used to determine the mortality of birds displaced by offshore windfarms in the UK.

After reviewing existing information on the displacement mortality rates, running an Expert Elicitation workshop to run elicit mortality rates and using SeabORD predictive model to simulate impacts of displacement and barrier effects, the project concludes:

That the displacement mortality rates generated via expert elicitation and SeabORD/emulation cannot be used within the Displacement Matrix tool currently used in many UK assessments, because of the differences in definition between the alternative approaches.

Our key recommendations are therefore for further work to understand site fidelity, and the impact of this upon displacement risk, to understand whether there is a potential for under-estimation of effects within the Displacement Matrix in relation to this process, by:

• Interrogation of GPS tracking data to estimate rates of fidelity in seabird species, including influence of environmental and seasonal variation.
• Examination of seabird time-activity budgets to understand influence of partitioning of behaviour between at-sea and colony behaviours and how this might be used to adjust at-sea survey data.
• Tracking of individual birds to link observed interactions with operational offshore windfarms with subsequent demographic rates.