Project alone: population-level impacts

3229. Based on the Developers Approach the potential loss of up to 2.1 gannets per year from the combined impacts arising from displacement and collisions equates to 0.004% of the breeding adult population.  This increases to up to 2.6 gannets per year; 0.005% of the adult population based on the Scoping A approach and 4.1 gannets per year based on Scoping B approach; equivalent to a 0.008% of the breeding adult population. These levels of impact could increase the baseline mortality rate from between 0.11% and 0.17%.
3230. This level of impact is not predicted to cause a population level effect to the breeding gannet population at the Hermaness, Saxa Vord and Valla Field SPA.

Project alone: Conclusion

3231. For both the Developer and Scoping Approaches, the potential effects from the Proposed Development alone on the Hermaness, Saxa Vord and Valla Field SPA gannet population are predicted to be small, with the resultant population-level impacts also predicted to be very small and at levels that would not impact on the population being of a similar size to that which would occur in the absence of the Proposed Development. Given this, it is concluded that the effects from the Proposed Development alone would not result in an adverse effect on this population.

Effects in-combination

Effects of relevance to the in-combination assessment

3232. For the same reasons as described in Effects in-combination for the Forth Islands SPA gannet population, the potential for effects of the Proposed Development to act on the Hermaness, Saxa Vord and Valla Field SPA gannet population in-combination with other plans and projects is limited to displacement/barrier effect and collision risk pathways during operation and maintenance.

Displacement/Barrier effects – operation and maintenance

3233. The approach and methods for estimating in-combination displacement mortality are described in Effects in-combination: Displacement/Barrier Effects – Operation and Maintenance for Forth Islands SPA gannet population above and in the Offshore EIA Report, volume 3, appendix 11.6, annex E.
3234. The potential mortality estimates derived for the other projects were combined with those for the Proposed Development to give in-combination estimates for the UK North Sea wind farm scenario, according to both the Scoping Approaches and Developer Approach ( Table 5.273   Open ▸ ).

Table 5.273: Estimated Annual Mortality of Hermaness, Saxa Vord and Valla Field SPA Gannets as a Result of Displacement From the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach, In-Combination With Other UK North Sea Wind Farms

3235. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult gannet from the Hermaness, Saxa Vord and Valla Field SPA population predicted due to displacement represents between approximately 0.027% of the current adult breeding population at this colony (i.e. 51,160 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report), as determined by Developers Approach and between 0.027% and 0.084% based on Scoping Approaches A and B. In terms of percentage increases in the baseline annual adult mortality of the population, the estimates of adult displacement mortality equate to an increase of 0.61% for developers approach and 0.61 – 1.81% for the lower and upper estimates from the Scoping Approach.

The potential levels of impact on the Hermaness, Saxa Vord and Valla Field SPA gannet population resulting from predicted displacement/barrier effects associated with the Proposed Development array area in-combination with other UK North Sea wind farms during the operation and maintenance phase are considered further below in the Project Alone: population-level impacts section. This presents the outputs from PVAs of the combined in-combination effects of predicted displacement and collision mortality on the SPA population.

Collision risk - operation and maintenance

3236. The approach and methods for estimating in-combination collision mortality are described in Effects in-combination: Collision – Operation and Maintenance for Forth Islands SPA gannet population above and in volume 3, appendix 11.6, annex E of the Offshore EIA Report.
3237. The potential mortality estimates derived for the other projects were combined with those for the Proposed Development to give in-combination estimates for the UK North Sea wind farm scenario, according to both the Scoping Approach and Developer Approach ( Table 5.274   Open ▸ ).

Table 5.274: Predicted Collision Effects on the Hermaness, Saxa Vord and Valla Field SPA Gannet Population Due to the Proposed Development In-Combination with Other Projects in UK North Sea Waters. Estimates are Presented for Both the Scoping Approach and Developer Approach for Consented Designs.

3238. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult gannets from the Hermaness, Saxa Vord and Valla Field SPA population predicted due to collisions represents 0.12% of the current adult breeding population at this colony (i.e. 51,160 individuals –Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by both the Developer Approach and Scoping Approaches. In terms of percentage increases in the baseline annual adult mortality of the population the estimates of adult collision mortality equate to an increase of 2.59% for the Developer Approach and 2.61% for the Scoping Approach.
3239. The potential levels of impact on the Hermaness, Saxa Vord and Valla Field SPA gannet population resulting from the predicted collision mortality associated with the Proposed Development in-combination with either the other UK North Sea wind farms during the operation and maintenance phase are considered in more detail below in the In- combination: population-level impacts section. This presents the outputs from PVAs of the combined effects of predicted displacement and collision mortality on the SPA population.

In-combination: population-level impacts

3240. PVA was undertaken on the mortality to the adult and immature age classes predicted due to the combined displacement and collision effects associated with the Proposed Development in-combination with the other North Sea wind farms. This was on the basis of the potential mortality as determined by both the Scoping and Developer Approaches (see Table 5.273   Open ▸ and Table 5.274   Open ▸ above).
3241. The approach to the PVA and the metrics used to summarise the PVA outputs are as described for In-combination: population-level impacts for Forth Islands SPA gannet population above and in volume 3, appendix 11.6 of the Offshore EIA Report.

Table 5.275: Projected 35 Year Population Sizes and Associated PVA Metrics for the Hermaness, Saxa Vord and Valla Field SPA Gannet Population Under Different Impact Scenarios for the Proposed Development In-Combination With Other UK North Sea Wind Farms

3242. The predicted in-combination population-level impacts are small, irrespective of whether these are determined using the Developer or Scoping Approaches. For Developer Approach the CPS value indicates that the combined collision and displacement mortality associated with the Proposed Development in-combination with estimated impacts with other North sea wind farms would result in a reduction of approximately 5.8% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects ( Table 5.275   Open ▸ ). Based on the Scoping Approach B the estimated reduction in the size of the population increases to approximately 8% after 35 years, relative to that in the absence of any wind farm effects ( Table 5.275   Open ▸ ). The associated reduction in annual population growth rate (relative to that predicted under baseline conditions) is estimated to be no greater than 0.2%, whilst the centile value of no less than 38.3 indicates a relatively large overlap in the distributions of the predicted impacted and unimpacted population sizes and, hence, a high likelihood of the impacted population being of a similar size to the unimpacted population after 35 years. As would be expected, the metrics for Scoping Approach A and the Developer Approach suggest smaller levels of impact ( Table 5.275   Open ▸ ).

In-combination: Conclusion

3243. On the basis of the Scoping Approach, the potential effects from the Proposed Development in-combination with other UK North Sea wind farms on the Hermaness, Saxa Vord and Valla Field SPA gannet population are predicted to be small, with the resultant population-level impacts also predicted to be relatively small. In addition, the PVA metrics indicate that it is likely that the population would be of a similar size to that which would occur in the absence of the Proposed Development after 35 years. The metrics for the Developer Approach suggest even smaller levels of impact. Considering this within the context of a highly precautionary assessment, it is concluded that the in-combination scenario for both the Scoping and Developer Approaches would not result in adverse effect on the Hermaness, Saxa Vord and Valla Field SPA gannet population.

Assessment for the breeding seabird assemblage

3244. The breeding seabird assemblage for the Hermaness, Saxa Vord and Valla Field SPA is a qualifying feature on the basis of the SPA supporting in excess of 20,000 individual seabirds. Great skua and gannet are amongst the species identified in the citation as having nationally important populations which contribute to the Hermaness, Saxa Vord and Valla Field SPA breeding seabird assemblage. No LSE was determined for the other species in relation to the Proposed Development (HRA Stage One Screening Report; SSER, 2021b).
3245. Potential impacts of the Proposed Development alone and in-combination with other UK North Sea wind farms on the breeding seabird assemblage for the SPA could arise via effects on the individual species within the assemblage feature. For both the Developer Approach and Scoping Approach, the assessments undertaken above identify no potential for an adverse effect on the SPA great skua or gannet population in relation to the Proposed Development alone and in-combination.
3246. Given the above, it is concluded that there is no potential for an adverse effect on the Hermaness, Saxa Vord and Valla Field SPA breeding seabird assemblage. This conclusion applies to the assessments undertaken according to both the Developer Approach and the Scoping Approach.

Site conclusion

3247. Based on both the Developer Approach and Scoping Approach it is concluded that the possibility of adverse effects can be discounted for the Hermaness, Saxa Vord and Valla Field SPA population of breeding great skua, gannet and breeding seabird assemblage qualifying feature.

5.7.20.              West Westray SPA

European Site Information and Conservation Objectives

3248. The West Westray SPA covers an area of 37.8 km2 and comprises an 8 km length of red sandstone cliffs on the western coast of the island of Westray, off the north coast of Orkney Mainland, approximately 355 km from the Proposed Development. The cliffed rocky coastline and maritime vegetation support large colonies of breeding seabirds. Approximately 91% of the SPA is marine environment with a seaward extension extending approximately 2 km into the marine environment. The SPA was classified in 1996, with the marine extension classified in 2009.
3249. The site qualifies under Article 4.2 by regularly supporting in excess of 20,000 breeding seabirds ( Table 5.276   Open ▸ ). The potential for LSE has been identified in relation to kittiwake and seabird assemblage ( Table 5.276   Open ▸ ), with the effect pathways associated with LSE for each of these detailed in Table 3.1   Open ▸ and set out in the assessment below.
3250. The Conservation Objectives of this SPA (as determined from NatureScot’s SiteLink (NatureScot 2022) are:

To avoid deterioration of the habitats of the qualifying species (listed below) or significant disturbance to the qualifying species, thus ensuring that the integrity of the site is maintained; and

To ensure for the qualifying species that the following are maintained in the long term:

• Population of the species as a viable component of the site
• Distribution of the species within site
• Distribution and extent of habitats supporting the species
• Structure, function and supporting processes of habitats supporting the species
• No significant disturbance of the species

3251. The Proposed Development does not overlap with the SPA, so that potential impacts on its qualifying features will only occur as a result of individuals from the colony occurring in the area (or vicinity) of the Proposed Development.
3252. Consequently, the focus of the assessment for this SPA population is concerned with the conservation objective to maintain or restore the populations of each qualifying feature because the other conservation objectives either apply to the site itself, and not to areas beyond the boundary, or are encompassed by the assessment of this conservation objective.
3253. Further information on this European site is presented in Appendix 3A.

Table 5.276: Details on the qualifying features of West Westray SPA

*Named components of the assemblage only.

Assessment for the Kittiwake Population

3254. The West Westray SPA kittiwake population is currently estimated to number 2,743, breeding pairs based on the most recent count in 2017. Kittiwake are listed on the West Westray SPA citation as a named component of the breeding seabird assemblage.
3255. Potential impacts on the West Westray SPA kittiwake population screened in for assessment are outlined in 3.1 and in the HRA Stage One Screening Report (SSE Renewables, 2021b).

The Potential for Impacts on the Kittiwake Population

3256. The breeding period for kittiwake is defined as mid-April to August, following the NatureScot (2020) guidance. From published information on kittiwake foraging ranges generally (Woodward et al., 2019) it is apparent that during the breeding period kittiwakes from West Westray SPA could occur in the vicinity of the Proposed Development. However, the findings of the apportioning exercise found that no kittiwakes occurring in the Proposed Development array area during the breeding season derived from this SPA (Offshore EIA Report, volume 3, appendix 11.5).
3257. In the non-breeding season kittiwakes are largely pelagic (Frederiksen et al., 2011), although most of those which breed on the North Sea coast likely winter in the North Sea and Celtic Sea. Therefore, it is likely that there is the potential for birds from the West Westray SPA population to pass through offshore wind farms in the North Sea during the autumn and spring passage periods (defined as September to December and January to mid-April, respectively - Furness 2015; NatureScot 2020; Offshore EIA Report, volume 3, appendix 11.5). Given the above, the Proposed Development may have potential effects on the West Westray SPA kittiwake population during the non-breeding passage periods only (Offshore EIA Report volume 3, appendix 11.5).

Project Alone: Construction and Decommissioning

Disturbance

3258. Direct disturbance to kittiwakes during the assumed eight-year construction phase may arise within the Proposed Development as a result of increased vessel movements, as well as from other activities associated with the installation of the turbine foundations, cables and other infrastructure (see the section on Project alone: construction and decommissioning disturbance for St. Abb’s Head to Fast Castle kittiwake population; Table 4.1).
3259. The potential for disturbance effects during decommissioning is assumed to be the same (or less) as for construction, noting that the duration of the decommissioning phase will not exceed that of construction, and may be shorter.
3260. Kittiwakes breeding at the West Westray SPA are not predicted to utilise the Proposed Development during the breeding season (Offshore EIA Report, volume 3, appendix 11.5). During the non-breeding periods, kittiwake distribution is not constrained by the location of the breeding colonies and birds from the SPA population are likely to occur across large expanses of oceanic and maritime waters (Frederiksen et al., 2012, Furness 2015). The potential for effects of construction- and decommissioning-related disturbance is therefore low.
3261. Furthermore, given the low sensitivity of kittiwake to disturbance effects (Garthe and Hüppop 2004; Furness et al., 2013), and the relatively small areas that will be subject to activities with the potential to result in intermittent, temporary disturbance (see the section on Project alone: construction and decommissioning – Disturbance for St. Abb’s Head to Fast Castle kittiwake population), it is considered that there is no potential for construction or decommissioning related disturbance to lead to an adverse effect on the West Westray SPA kittiwake population. This conclusion is consistent with the outcome of the EIA which ‘screened’ out kittiwake as a species for which detailed consideration of the effects of construction disturbance was required (Offshore EIA Report, volume 2 Chapter 11).

Displacement

3262. As detailed above, kittiwake is considered to have a low sensitivity to disturbance (Garthe and Hüppop 2004; Furness et al., 2013), and potential effects of disturbance during the construction and decommissioning phases will only extend across a very small part of the wider foraging areas used by the West Westray SPA kittiwake population during the non-breeding season. Furthermore, as detailed in the section on Project alone: construction and decommissioning– Displacement for St. Abb’s Head to Fast Castle kittiwake population, potential effects of disturbance will not occur simultaneously across the entirety of the Proposed Development array area and offshore export cable corridor but will instead be carried out in different areas at different times. Thus, at any given time the potential for disturbance effects that could lead to displacement of kittiwake from this SPA during the non-breeding periods will be limited to relatively small areas, with the potential effects also being of a temporary nature.
3263. Therefore, it is considered that there is no potential for construction or decommissioning related displacement to lead to an adverse effect on the West Westray SPA kittiwake population.

Changes to Prey Availability

3264. During construction and decommissioning there are a number of ways in which effects on key prey species of seabirds may occur, which are outlined in the section on Project Alone: Construction and Decommissioning – Changes to prey availability for the St Abb’s Head to Fast Castle SPA kittiwake population. The same evidence basis and context applies to the West Westray SPA kittiwake population as to the St Abb’s Head to Fast Castle SPA population in relation to the potential for such effects to lead to impacts on the population.
3265. Given this, it is considered that there is no potential for the West Westray SPA kittiwake population to be affected by changes to prey availability during the construction and decommissioning phases, with any such effects being largely intermittent across a relatively small spatial extent, with most effects temporary in nature. Consequently, it is considered that there is no potential for construction or decommissioning related changes in prey availability to lead to an adverse effect on the West Westray SPA kittiwake population.

Project Alone: Operation and Maintenance

Disturbance

3266. Vessel use and associated activities within the Proposed Development array area and export cable corridor during the operation and maintenance phase may lead to direct disturbance of kittiwakes from West Westray SPA during the non-breeding periods, as outlined in the section on Project Alone: Operation and Maintenance – Disturbance for the St. Abb’s Head to Fast Castle SPA kittiwake population. The same evidence base and context applies to the West Westray SPA kittiwake population as to the St Abb’s Head to Fast Castle SPA population in relation to the potential for such effects to lead to impacts on the population during the non-breeding periods.
3267. Given the discrete areas relative to the species’ non-breeding season foraging range that will be subject intermittently to potential disturbance from vessel use and maintenance activities, and the fact that these potential effects will be reduced compared to the construction and decommissioning phases, it is considered that there is no potential for disturbance during operation and maintenance to lead to an adverse effect on the West Westray SPA kittiwake population.

Displacement / Barrier Effects

3268. The approach used to derive predicted levels of mortality for West Westray SPA kittiwakes is as described in the section on Project Alone: Operation and Maintenance – Displacement/barrier effects for the St Abb’s Head to Fast Castle SPA kittiwake population (and in Offshore EIA Report volume 3, appendix 11.4)
3269. Estimates of kittiwake mortality for West Westray SPA were produced using the SNCB matrix on the basis of both the Scoping Approaches and the Developer Approach (Offshore EIA Report volume 3, appendix 11.4), with these estimates then apportioned to the West Westray SPA kittiwake population as described in volume 3, appendix 11.5 of the Offshore EIA Report and in the section on Project Alone: Operation and Maintenance – Displacement/barrier effects for the St Abb’s Head to Fast Castle SPA kittiwake population ( Table 5.277   Open ▸ ).

Table 5.277: The mean peak abundance estimates of kittiwake in the Proposed Development array area and 2 km buffer for each seasonal period, together with the proportion of birds estimated to belong to the breeding adult age class and to be from the West Westray SPA population in each period. The proportion of adults assumed to be sabbaticals during the breeding season is also presented.

Table 5.278: Estimated potential annual mortality of West Westray SPA kittiwakes as a result of displacement from the Proposed Development array area and 2 km buffer as determined by the Scoping Approach and Developer Approach.

3270. The potential annual mortality as a result of displacement is estimated as 1.5 adult and 0.8 immature birds based on Scoping Approach A and as 4.6 adult and 2.3 immature birds based Scoping Approach B ( Table 5.278   Open ▸ ). All mortality was attributable to the non-breeding periods.
3271. No mortality from displacement was predicted using the Developer Approach for any age class or season ( Table 5.278   Open ▸ ).
3272. The additional annual mortality of adult kittiwakes from the West Westray SPA population predicted due to displacement from the Proposed Development array area represents 0.03% of the current adult breeding population at this colony (i.e. 5,486 individuals) as determined by Scoping Approach A, and 0.08% as determined by Scoping Approach B. In terms of percentage increases in the baseline annual adult mortality of the population (based on applying a mortality rate of 0.188 see Table 2.13 of volume 3, appendix 11.6 of the Offshore EIA Report), the estimates of adult mortality equate to an increase of 0.14 – 0.44% for the lower and upper estimates from the Scoping Approach.  As outlined above and in Table 5.278   Open ▸ , no mortality was predicted using the Developer Approach.

Collision Risk

3273. The approach used to derive predicted levels of mortality for West Westray SPA kittiwakes is as described in the section on Project Alone: Operation and Maintenance – Collision risk for the St Abb’s Head to Fast Castle SPA kittiwake population (and in Offshore EIA Report, volume 3, appendix 11.3)
3274. Based upon option 2 of the deterministic CRM with a 98.9% avoidance rate applied, the annual collision mortality of kittiwakes from the West Westray SPA is predicted to be approximately 5.4 adults and 2.5 immatures as determined by the Scoping Approach, and approximately 7.4 adults and 3.7 immatures as determined by the Developer Approach Table 5.279   Open ▸ ). All mortality was attributable to the non-breeding periods.

Table 5.279: Predicted collision effects from the Proposed Development on the West Westray SPA kittiwake population, as determined by the Scoping Approach and Developer Approach. Estimates are for the worst-case design and are based on option 2 of the deterministic CRM using a 98.9% avoidance rate.

3275. The additional annual mortality of adult kittiwakes from the West Westray SPA population predicted due to collision represents approximately 0.09% of the number of adults currently estimated to breed at this colony (i.e. 5,486 individuals) as determined by the Developer Approach and approximately 0.13% as determined by the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying the mortality rate of 0.188 – see Table 2.13 of volume 3, appendix 11.6 of the Offshore EIA Report), the predicted adult collision mortality equates to increases of 0.52% and 0.71% for the Developer and Scoping Approaches, respectively.
3276. As outlined in the Project Alone: Operation and Maintenance - Collision Risk section for the St Abb’s Head to Fast Castle SPA kittiwake population, using the collision estimates derived from the site-specific flight height data or from the stochastic CRM with avoidance rates as calculated for the bird collision-avoidance study (Bowgen and Cook 2018) would result in predicted collision mortalities on the West Westray SPA kittiwake population that are at least 50% lower than those presented in Table 5.279   Open ▸ above (and on which the assessment is based).
3277. The potential levels of impact on the West Westray SPA kittiwake population resulting from predicted collision mortality associated with the Proposed Development array area during the operation and maintenance phase are considered further below in the Project Alone: Population-Level Impacts section. This presents the outputs from PVAs of the combined effects of predicted displacement and collision mortality on the SPA population.

Changes to Prey Availability

3278. During the operational and maintenance phase there are a number of ways in which effects on key prey species may occur, which are outlined in the section on Project Alone: Construction and Decommissioning – Changes to Prey Availability for the St Abb’s Head to Fast Castle SPA kittiwake population. The same evidence base and context applies to the West Westray SPA kittiwake population as to the St Abb’s Head to Fast Castle SPA population in relation to the potential for such effects to lead to impacts on the population.
3279. Given this, it is considered that there is no potential for the West Westray SPA kittiwake population to be affected by changes to prey availability during the operation and maintenance phase, with any such effects being largely intermittent across a relatively small spatial extent. Consequently, it is considered that there is no potential for operational or maintenance related changes in prey availability to lead to an adverse effect on the West Westray SPA kittiwake population.

Project Alone: Population-Level Impacts

3280. As determined above, the effects from the Proposed Development alone which could lead to an adverse effect on the West Westray SPA kittiwake population are displacement (inclusive of barrier effects) and collision mortality during the operation and maintenance phase.
3281. PVA was therefore undertaken on the mortality to the adult and immature age classes predicted due to the combined displacement and collision effects associated with the Proposed Development, as determined by both the Scoping and Developer Approaches (see Table 5.278   Open ▸ and Table 5.279   Open ▸ above). The approach and methods to undertaking the PVA are as described in the section on Project Alone: Project alone: population-level impacts for St Abb’s Head to Fast Castle SPA kittiwake population above and in volume 3, appendix 11.6 of the Offshore EIA Report. Mean annual productivity was calculated based on annual breeding success data from the West Westray SPA in the period 2010-2021. It should be noted that this period encapsulates a crash in kittiwake productivity in the early 2010s which was seen across Orkney breeding colonies. Productivity has subsequently increased, with productivity at the West Westray SPA back to pre-crash levels in recent years (SMP, 2022). Outputs of the PVA should therefore be viewed in this light. The starting population size was the 2021 count for the SPA (Offshore EIA Report, volume 3, appendix 11.5).

Table 5.280: Projected 35 year population sizes and associated PVA metrics for the West Westray SPA kittiwake population under different impact scenarios for the Proposed Development alone.

3282. The PVA predicted a continuing population decrease for the West Westray SPA kittiwake population, irrespective of the effects from the Proposed Development. Thus, the population is predicted to be smaller than the current estimate of 5,486 adult birds under all scenarios, including baseline which assumes no wind farm effects ( Table 5.280   Open ▸ ). However, this decrease is likely to be strongly influenced by the mean annual productivity rate used within the model, which does not capture the recovery of this breeding population seen in recent years (SMP, 2022).
3283. The predicted population-level impacts are small, irrespective of whether these are determined using the Developer or Scoping Approaches. Thus, for Scoping Approach B the CPS value indicates that the combined collision and displacement mortality associated with the Proposed Development alone would result in a reduction of approximately 8.8% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects ( Table 5.280   Open ▸ ). The associated reduction in annual population growth rate (relative to that predicted under baseline conditions) is estimated to be 0.3%, whilst the centile value of 46.2 indicates a considerable overlap in the distributions of the predicted impacted and unimpacted population sizes and, hence, a high likelihood of the impacted population being of a similar size to the unimpacted population after 35 years. As would be expected, the metrics for Scoping Approach A and the Developer Approach suggest smaller levels of impact ( Table 5.280   Open ▸ ).

Project Alone: Conclusion

3284. For both the Developer and Scoping Approaches, the potential effects from the Proposed Development alone on the West Westray SPA kittiwake population are predicted to be small, with the resultant population-level impacts also predicted to be small. Any impacts are likely to be within the natural variation of the population. Given this, it is concluded that the effects from the Proposed Development alone would not result in an adverse effect on this SPA population.

Effects In-Combination

Effects of relevance to the in-combination assessment

3285. For the same reasons as described in Effects In-Combination for the St. Abb’s Head to Fast Castle SPA kittiwake population, the potential for effects of the Proposed Development to act on the West Westray SPA kittiwake population in-combination with other plans and projects is limited to displacement/barrier effect and collision risk pathways during operation and maintenance.
3286. In-combination totals have been collated for all relevant SPA populations for all UK North Sea offshore wind farms in operation, construction, consented or planning (volume 3, appendix 11.6, annex E of the Offshore EIA Report). Separate in-combination totals for the Forth and Tay projects were not collated for the reasons outlined in Effects in-combination for the Farne Islands SPA kittiwake population volume 3, appendix 11.6, annex E and volume 3, appendix 11.8 of the Offshore EIA Report.

Displacement / Barrier Effects – Operation and Maintenance

3287. The approach and methods for estimating in-combination displacement mortality are described in Effects In-Combination: Displacement/barrier effects – operation and maintenance for St Abb’s Head to Fast Castle SPA kittiwake population above and in Offshore EIA Report volume 3, appendix 11.6, annex E.
3288. The potential mortality estimates derived for the other projects were combined with those for the Proposed Development to give in-combination estimates for the UK North Sea wind farm scenario, according to both the Scoping Approaches and Developer Approach ( Table 5.281   Open ▸ ).

Table 5.281: Estimated annual mortality of West Westray SPA kittiwakes as a result of displacement from the Proposed Development array area and 2 km buffer as determined by the Scoping Approach and Developer Approach, in-combination with other UK North Sea wind farms.

3289. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult kittiwakes from the West Westray SPA population predicted due to displacement represents between approximately 0.14-0.43% of the current adult breeding population at this colony (i.e. 5,486 individuals), as determined by Scoping Approach A and B. In terms of percentage increases in the baseline annual adult mortality of the population, the estimates of adult displacement mortality equate to an increase of 0.76 - 2.27% for the lower and upper estimates from the Scoping Approach. No mortality of kittiwake from displacement effects is predicted to occur following the Developer Approach.
3290. The potential levels of impact on the West Westray SPA kittiwake population resulting from predicted displacement/barrier effects associated with the Proposed Development array area in-combination with other UK North Sea wind farms during the operation and maintenance phase are considered further below in the Project In-combination: Population-Level Impacts section. This presents the outputs from PVAs of the combined in-combination effects of predicted displacement and collision mortality on the SPA population.

Collision Risk - Operation and Maintenance

3291. The approach and methods for estimating in-combination collision mortality are described in Effects In-Combination: Collision – Operation and Maintenance for St Abb’s Head to Fast Castle SPA kittiwake population above and in volume 3, appendix 11.6, annex E of the Offshore EIA Report.
3292. The potential mortality estimates derived for the other projects were combined with those for the Proposed Development to give in-combination estimates for the UK North Sea wind farm scenario, according to both the Scoping Approach and Developer Approach ( Table 5.282   Open ▸ ).

Table 5.282: Predicted collision effects on the West Westray SPA kittiwake population due to the Proposed Development in-combination with other projects in the UK North Sea waters. Estimates are presented for both the Scoping Approach and Developer Approach for consented designs.

3293. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult kittiwakes from the West Westray SPA population predicted due to collisions represents 0.74% of the current adult breeding population at this colony (i.e. 5,486 individuals) as determined by the Developer Approach, and 0.77% of this population as determined by the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population, the estimates of adult collision mortality equate to an increase of 3.89% for the Developer Approach and of 4.1% for the Scoping Approach.
3294. The potential levels of impact on the West Westray SPA kittiwake population resulting from predicted collision mortality associated with the Proposed Development array area in-combination with other UK North Sea wind farms during the operation and maintenance phase are considered further below in the Project In-combination Population-Level Impacts section. This presents the outputs from PVAs of the combined in-combination effects of predicted displacement and collision mortality on the SPA population.

In-Combination: Population-Level Impacts

3295. As for the Proposed Development alone, PVA was undertaken on the mortality to the adult and immature age classes predicted due to the combined displacement and collision effects associated with the Proposed Development in-combination with the other UK North Sea wind farms. This was on the basis of the potential mortality as determined by both the Scoping and Developer Approaches (see Table 5.281   Open ▸ and Table 5.282   Open ▸ above).
3296. The approach to the PVA and the metrics used to summarise the PVA outputs are as described for In-Combination: Population-Level Impacts for St Abb’s Head to Fast Castle SPA kittiwake population above and in volume 3, appendix 11.6 of the Offshore EIA Report. As for the project alone PVA, mean annual productivity was calculated based on annual breeding success data from the West Westray SPA in the period 2010-2021. This period encapsulates a crash in kittiwake productivity in the early 2010s which was seen across Orkney breeding colonies. Productivity has subsequently increased, with productivity at the West Westray SPA back to pre-crash levels in recent years (SMP, 2022). Outputs of the in-combination PVA should therefore be viewed in this light (SMP, 2022).
3297. It is also noted that the predicted unimpacted population after 35 years of 47 adults will be significantly lower than the current population of 5,486 adults.  Although the additional mortality caused by the Proposed Development in-combination may have a relatively large impact when measured against the Counterfactual Population Size the overall in-combination impact will not have any material effect to the size of colony when compared to the significant decline predicted by the PVA modelling to an unimpacted population.

Table 5.283: Projected 35 year population sizes and associated PVA metrics for the Coquet Island SPA kittiwake population under different impact scenarios for the Proposed Development in-combination with the other UK North Sea wind farms.

3298. Given that the in-combination effects are inevitably greater than those for the Proposed Development alone, the PVA metrics for the Proposed Development in-combination with other UK North Sea wind farms suggest greater population-level impacts than as predicted for the Proposed Development alone (compare Table 5.280   Open ▸ with Table 5.283   Open ▸ ). However, this these predicted impacts are likely to be strongly influenced by the mean annual productivity rate used within the model, which does not capture the recovery of this breeding population improved productivity seen in kittiwake colonies across Orkney in recent years (SMP, 2022).
3299. The CPS value for the Developer Approach indicates that the SPA population size would be reduced by 26.6% relative to the predicted population size under baseline conditions after 35 years, whilst the equivalent reduction for the Scoping Approach is 32.3 – 40.1% ( Table 5.283   Open ▸ ). Reductions in the annual population growth rate (relative to that predicted under baseline conditions) are estimated to be 0.9% for the Developer Approach and 1.1 – 1.4% for the Scoping Approach. The values for the centile metric are estimated as 38.1 after 35 years for the Developer Approach and as 30.6 – 34.9 for the Scoping Approach, suggesting moderate levels of overlap in the distribution of the predicted impacted and unimpacted population sizes and, hence, a reasonable likelihood of the impacted population being smaller than the unimpacted population after 35 years (noting the influence of productivity rates on these outputs).

In-Combination: Conclusion

3300. For both the Scoping and Developer Approaches, the predicted levels of impact associated with the in-combination scenario represent a marked increase compared to those associated with the Proposed Development alone. These levels of impact suggest the potential for the in-combination effects to lead to a marked reduction in the size of the West Westray SPA population after 35 years relative to that which would occur in the absence of these effects. The predicted levels of impact are such that for the Developer Approach (which predicts lower levels of impact than the Scoping Approach), this potential reduction in population size is 26.6% for the Proposed Development in-combination with the other UK North Sea wind farms.
3301. The centile values indicate a moderate likelihood of the impacted population being similar in size to the un-impacted population after 35 years whilst the context that has been outlined in for both St. Abb’s Head to Fast Castle SPA and Forth Islands SPA in relation to (i) the high levels of precaution incorporated in the assessment and (ii) the likelihood that the effects from wind farm developments will be of minor importance relative to other management and environmental factors in determining the future status of the SPA kittiwake population remains highly relevant.
3302. Furthermore, the outputs of the West Westray SPA are considered to be highly influenced by the mean productivity rate for the colony, which does not reflect the current levels of productivity recorded in recent years. Given that current productivity rates for this SPA are in line with those seen prior to the 2008 Orkney population crash (SMP, 2022), it is considered that the scale of the potential reduction in the size of the SPA population is an artefact of the PVA methodology.
3303. Consequently, it is concluded that there is the potential for an adverse effect on the West Westray SPA kittiwake population as a result of the predicted effects from the Proposed Development in-combination with the other UK North Sea wind farms. This conclusion applies to the assessments undertaken according to both the Developer Approach and the Scoping Approach.

Assessment for the Breeding Seabird Assemblage

3304. The breeding seabird assemblage for the West Westray SPA is a qualifying feature on the basis of the SPA supporting in excess of 20,000 individual seabirds (with the citation also noting that the SPA regularly supports 113,000 seabirds). Kittiwake comprise one of the six species identified in the citation as having populations which are considered to be of European or national importance and which contribute to the West Westray SPA breeding seabird assemblage (no LSE was determined for the other five species in relation to the Proposed Development (HRA Stage One Screening Report; SSE Renewables, 2021b).
3305. Potential impacts of the Proposed Development in-combination with other UK North Sea wind farms on the breeding seabird assemblage for the SPA could arise via effects on the individual species within the assemblage feature. For the both the Developer Approach and Scoping Approach, the assessments undertaken above identify no potential for adverse effects on the SPA kittiwake population.
3306. For the in-combination scenario as determined by the Developer Approach and Scoping Approach, the outputs have been considered in light of the high levels of precaution incorporated in the assessment and with the issues surrounding the mean productivity rate for this SPA, together with the likelihood that the effects from wind farm developments will be of minor importance relative to other management and environmental factors in determining the future status of the SPA kittiwake population. On this basis it is considered that there is no potential adverse effect from in-combination impacts on the SPA kittiwake population in which could lead to a subsequent adverse effect on the seabird assemblage.

Site Conclusion

3307. It is concluded that an AEoI of the West Westray SPA can be excluded from the Proposed Development in-combination with other plans and projects.

5.8. Appropriate Assessment: Migratory Waterbirds SPAs

5.8.1.    Approach

3308. In response to the 2020 Berwick Bank Scoping Report (SSER, 2020), NatureScot and MSS advised that assessment of collision risk to migratory species should be undertaken qualitatively with reference to the MSS commissioned strategic level report (WWT Consulting, 2014). NatureScot and MSS noted in their Scoping Opinion representations that MSS were in the process of commissioning a further strategic study of migratory species collision risk and that this should be used if available (MS-LOT, 2021).
3309. Subsequently, it was noted during Roadmap Meeting 4 (Offshore EIA Report, volume 3, appendix 11.8, annex A) that some species that are qualifying features of the designated sites screened in were not included within the MSS strategic level report (WWT Consulting, 2014). NatureScot advised that assessment for these missing species was still required and that this should be done on a qualitative basis (G.Holland, email 14/01/2022). Additional methodological work for these species was, therefore, developed in this assessment to allow similar qualitative summaries to be included for the species noted.
3310. The quantitative results presented within the MSS strategic level report are no longer accurate as a result of design changes for the offshore wind farms considered within that report during their development and consenting processes, along with updates on avoidance rate values for some of the species scoped into this report. Since an update to the MSS strategic level report has not been published to date, these changes are incorporated within the approach outlined in this assessment to ensure that the outcomes presented are more representative of the current scale of offshore wind farms present along the Scottish east coast.
3311. The MSS strategic level report provides estimations of the risk of collision to 38 migratory non-seabird species from 11 Scottish offshore wind farms, where details were available during the report’s commissioning. Using a proportional overlap approach based on the footprint of offshore wind farms and the migratory routes of certain species, the MSS strategic level report provides estimates of annual collisions, allowing for an avoidance rate of 98%, of migratory species within Scotland from the given offshore wind farms. The MSS strategic level report uses total passage population to consider total birds that may be exposed to potential effects from wind farm developments during the spring and autumn migrations. The passage population size is, therefore, not directly attributable to local SPAs, with individuals within the passage populations potentially associating with SPAs within the UK and Ireland, but not screened in for the Proposed Development, or breeding on mainland Europe. The outcomes of the MSS strategic level report were used to calculate the increase above the natural baseline mortality for each migratory population. Increases above baseline mortality were calculated by dividing the number of predicted collisions from the MSS strategic level report by the number of expected natural baseline mortalities, which were calculated using the population size and adult survival rates available within the British Trust for Ornithology’s (BTO) BirdFacts (Robinson, 2005).
3312. Several of the offshore wind farms used in the MSS strategic level report have since changed key design parameters (i.e. number of wind turbine generators (wind turbines) and/or the offshore wind farm footprint), which has direct effects on collision risk mortality estimates. Updated values were, therefore, collated to enable this assessment to qualitatively assess species’ risk within the Proposed Development array area both alone and in the context of potential in-combination effects as described within the MSS strategic level report. Table 5.284   Open ▸ details the changes in wind turbine numbers that were available within the relevant development’s published documents. Increases in baseline mortality and the comparative decreases wind turbine associated with the number of wind turbines used for these estimates are used to determine whether further analysis is required. The details for the Proposed Development are added to the updated values for the wind farms contained within the MSS strategic level report for this report only, the Proposed Development was not included within the MSS strategic level report ( Table 5.284   Open ▸ ).
3313. Due to the substantial decrease in the number of wind turbines and the likely associated decreases in collision risk if the MSS strategic level report was to be fully revised, the increase in baseline mortality values calculated for each species were multiplied by 0.7 to account for the decrease in wind turbines. A threshold of 0.95% adjusted increased baseline mortality was then used as a threshold for species to be assessed further. A value slightly under the 1% additional mortality threshold used within the MSS strategic level report was considered to be suitably precautionary. Details on species-specific survival rates, sourced from BTO online data, can be found in appendix 3A.
3314. Calculating the mortality rates based on the passage population and estimated collision numbers presented within the MSS strategic level report would provide increased mortality rates of significantly lower (approximately half) of the true effect on the population. It is reasonable to assume that the majority of the same individuals migrate through the area twice, and not as a single exposure. Therefore, to ensure that the approach is fully precautionary and to appropriately calculate the increase in baseline mortality, only one seasonal passage population should be used. Here, we used whichever seasonal migration was the largest for the given species.
3315. For species above the 0.95% adjusted threshold, further literature reviews were undertaken to understand the risk posed by the Proposed Development. The literature review focussed on updated avoidance rates for the species of concern as the values used within the MSS strategic level report are now considered overly precautionary (Natural England, 2022) along with available population information. Any potential impacts are considered within the context of consented or proposed developments within the region and the size of the screened in SPA populations within the context of the passage population used within the MSS strategic level report.
3316. There were 17 species screened in for this assessment that were not included within the MSS strategic level report full analysis. As detailed within the MSS strategic level report, this is predominantly due to a lack of data on population numbers in Scotland during spring and autumn passage periods and therefore no collision risk modelling work could be undertaken. For those species, the migratory routes obtained from BTO SOSS 05 (Wright et al., 2012), SPA population size, extent of migratory path and collision risk outputs for proxy species within the MSS strategic level report are considered to inform the risk.
3317. For these species, it was assumed that all colonies received a uniform selection of individuals using the migratory route. This enabled a calculation of the percentage the migratory front overlapped with the Proposed Development (overlap proportion). The most recently available avoidance rates were then considered to assess whether any reductions in the number of annual estimated collisions would be likely if migratory collisions were re-analysed using the most up to date values. The number of birds was then considered against the passage population size used within the MSS strategic level report and the population size of the SPA, along with migratory routes and other offshore wind farms to allow a qualitative analysis to be presented. Further analysis to the collision risk modelling level is not considered due to the advice received (G.Holland, email 14/01/2022) as well as uncertainties in the specific migratory behaviours of the screened in SPA populations.
3318. For species which had no robust estimates of migratory paths (one of the criteria for being dropped from the MSS strategic level report), migratory front information or other missing data were used from a proxy species. Proxies were determined based on species similarity, UK population sizes, and utilisation of the same protected sites. It is emphasised that the outputs of these are qualitative and are constrained by data availability limiting full analysis. For barrier effects, spatial overlaps were reviewed regarding migration direction and the Proposed Development array area used to consider potential increases in migration distance.

Table 5.284: Details on the Offshore Wind Farms Assessed Under the MSS Strategic Level Report. Updated Details are Obtained from the Most Recent Assessment and Consenting Documents Available Online

* Moray Firth Round 3 sites as described in MSS strategic level report. Turbine numbers updated with developments that most closely match the area used within the MSS strategic level report analysis.