Displacement

1989. As detailed above, guillemot is considered to have a moderate sensitivity to disturbance, whilst potential effects of disturbance during the construction and decommissioning phases will (at most) only extend across a small part of the wider foraging areas used by the Buchan Ness to Collieston Coast SPA guillemot population and be limited to (at most) an eight year period during construction (and a likely similar or shorter period during decommissioning). Furthermore, as detailed above, potential effects of disturbance will not occur simultaneously across the entirety of the Proposed Development array area or Proposed Development export cable corridor but, rather, will 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 guillemots from this SPA will be limited to relatively small areas (which, relative to guillemot foraging range, are distant to the SPA), with the potential effects also being of a temporary nature.
1990. Based upon the above, it is considered that there is relatively little potential for the Buchan Ness to Collieston Coast SPA guillemot population to be affected by displacement during the construction or decommissioning phases, with any such effects only extending across relatively small areas and tending to be temporary in nature. Consequently, it is considered that there is no potential for construction or decommissioning related displacement to lead to an adverse effect on the Buchan Ness to Collieston Coast SPA guillemot population.

Changes to prey availability

1991. Sandeels are key prey for guillemots, with a range of other species taken including clupeids (sprat and juvenile herring; del Hoyo et al., 1996). Indirect effects on guillemots may arise as a result of changes in the availability, distribution, or abundance of these species during the construction and decommissioning phases of the Proposed Development. Reduction or disruption to prey availability may cause displacement from foraging grounds or reduced energy intake, affecting survival rates or productivity in the Buchan Ness to Collieston Coast SPA guillemot population in the short-term.
1992. 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 evidence base and context for assessing the potential for such effects to have impacts on the Buchan Ness to Collieston Coast SPA guillemot population are as for the St Abb’s Head to Fast Castle SPA guillemot population (and are detailed above in the equivalent section for that SPA population). Additionally, the relatively large distance of the Proposed Development from the Buchan Ness to Collieston Coast SPA is relevant because it reduces the likelihood that guillemots from this SPA will use the Proposed Development (Offshore EIA Report, volume 3, appendix 11.5).
1993. Given this, it is considered that there is relatively little potential for the Buchan Ness to Collieston Coast SPA guillemot 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 Buchan Ness to Collieston Coast SPA guillemot population.

Project alone: operation and maintenance

Disturbance

1994. 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 guillemots from Buchan Ness to Collieston Coast SPA. As described in the section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population, guillemots are considered to have a moderate sensitivity to such sources of direct disturbance at sea (Garthe and Hüppop 2004, Furness et al., 2013).
1995. The maximum design scenario is for up to 3,393 vessel round trips per year over the operational lifetime of the project. Vessel types which will be required during the operation and maintenance phase include those used during routine inspections, repairs and replacement of equipment, major component replacement, painting or other coatings, removal of marine growth, replacement of access ladders, and geophysical surveys (Table 4.1).
1996. Based on information presented in the section on Project Alone: Operation and Maintenance – Disturbance for the St Abb’s Head to Fast Castle SPA kittiwake population and in the Offshore EIA Report, volume 2, chapter 13, baseline levels of vessel traffic in the Offshore Ornithology study area are relatively high. In the context of the baseline levels of vessel traffic across the Offshore Ornithology study area, the increase during the operation and maintenance phase is considered to be relatively small. Vessel movements will be within the Proposed Development array area and export cable corridor and will follow existing shipping routes to/from ports. In addition, Project Codes of Conduct included as a part of the NSVMP (Offshore EIA Report, volume 4, appendix 25) will be issued to all project vessel operators to avoid sudden changes in course or speed which will minimise the potential for disturbance. Within the Proposed Development array area, movements and associated maintenance activities will be restricted to individual wind turbines over a period of days to weeks.
1997. The size and noise outputs from vessels during the operation and maintenance phase will be similar to those used in the construction phase. However, the number of vessel return trips per year and their frequency will be much lower for the operation and maintenance phase compared to the construction phase. In addition, activities during the operation and maintenance phase will not occur simultaneously across the entirety of the Proposed Development array area and export cable corridor but intermittently within discrete (often very small) parts of these wider areas.
1998. Given the discrete areas relative to the species’ foraging range that will be subject intermittently to potential disturbance from vessel use and maintenance activities (Woodward et al., 2019), 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 Buchan Ness to Collieston Coast SPA guillemot population.

Displacement/barrier effects

1999. As outlined above, displacement effects on the Buchan Ness to Collieston Coast SPA guillemot population are estimated using the SNCB matrix approach, as applied to the Proposed Development array and two kilometre buffer (SNCBs 2022, Offshore EIA Report, volume 3, appendix 11.4). Thus, throughout this section, mortality from displacement is assumed to refer to that which results from both displacement and barrier effects. The approach used to derive predicted levels of mortality 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 above (and in the Offshore EIA Report, volume 3, appendix 11.4).
2000. On the basis of the advice provided in the Scoping Opinion (volume 3, appendix 6.2 of the Offshore EIA Report, displacement effects on guillemot are estimated for the breeding and non-breeding periods. The displacement and associated mortality rates advised in the Scoping Opinion (subsequently termed the Scoping Approach) for guillemot are:

• Breeding period: 60% displacement with lower and upper mortality rates of 3% and 5%.
• Non-breeding period: 60% displacement with lower and upper mortality rates of 1% and 3%.
  2001. As with other species for which displacement effects are assessed (see above), the approach to estimating guillemot displacement effects advocated by the Scoping Opinion was considered overly precautionary in relation to both the displacement and mortality rates that were proposed, with these rates being higher than is considered to be justified on the basis of the available evidence (even when allowing for the incorporation of precaution in the assessment - volume 3, appendix 11.4, annex G of the Offshore EIA Report). Furthermore, the mortality rates advocated by the Scoping Opinion represented a marked change from the assumptions applied in assessments for other recent Scottish offshore wind farms (Marine Scotland 2017a,b,c) with no clear evidence apparently being available to justify such a change.
  2002. Based upon a consideration of the available evidence for guillemot displacement, the potential consequent mortality, previous precedent and a need to incorporate precaution within the assessment, an alternative Developer Approach to estimating displacement effects was determined (volume 3, appendix 11.4, annex G of the Offshore EIA Report). The rates adopted by the Developer Approach are:
• Breeding period: 50% displacement with a mortality rate of 1%.
• Non-breeding period: 50% displacement with a mortality rate of 1%.
  2003. Estimates of guillemot mortality were produced using the SNCB matrix on the basis of both the Scoping Approach and the Developer Approach (Offshore EIA Report, volume 3, appendix 11.4), with these estimates then apportioned to the Buchan Ness to Collieston Coast SPA guillemot population during the breeding and non-breeding periods according to the MS Apportioning Tool (Butler et al. 2020) and the NatureScot (2018) approach, respectively (Offshore EIA Report, volume 3, appendix 11.5, Table 5.140). The resulting mortality estimates for the breeding and non-breeding periods were apportioned to age classes on the basis of the asymptotic age distribution of the population model used for the Buchan Ness to Collieston Coast SPA guillemot PVAs in this assessment (Offshore EIA Report, volume 3, appendix 11.6). Based on advice provided by NatureScot and Marine Scotland Science following Roadmap Meeting 4 (G. Holland, email 26/01/2022), it was also assumed that 7% of the breeding adults in the SPA population miss breeding in any given year (i.e. sabbatical birds) so that the number of estimated adult deaths during the breeding season was adjusted accordingly.

Table 5.140: The Mean Peak Abundance Estimates of Guillemot 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 Buchan Ness to Collieston Coast SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals During the Breeding Season is also Presented

2004. Based upon the estimates and assumptions detailed above, the potential annual mortality amongst the SPA guillemot population as a result of displacement is estimated as 10 adult and nine immature birds based on the lower mortality rates for the Scoping Approach (i.e. Scoping Approach A) and as 22 adult and 20 immature birds based upon the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B) (Table 5.141). These effects are relatively evenly split between the breeding and non-breeding periods (Table 5.141).
2005. The annual mortality from displacement as determined using the Developer Approach is predicted to be five adult and five immature birds, equating to 50% and 23% of the mortality predicted for the lower and upper range of the Scoping Approach, respectively (Table 5.141). The breeding season effects represent approximately one third of the total annual mortality, as determined by the Developer Approach.

Table 5.141: Estimated Potential Annual Mortality of Buchan Ness to Collieston Coast SPA Guillemots as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach

2006. The additional annual mortality of adult guillemot from the Buchan Ness to Collieston Coast SPA population predicted due to displacement from the Proposed Development array represents 0.01% of the current adult breeding population at this colony (i.e. 39,553 individuals – Table 3.3 in the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and between approximately 0.02 - 0.05% of this population as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.073 – see Table 2.9 in the Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult mortality equate to an increase of 0.2% for the Developer Approach and of 0.3 – 0.7% for the lower and upper estimates from the Scoping Approach.
2007. The potential levels of impact on the Buchan Ness to Collieston Coast SPA guillemot population resulting from the mortality predicted from displacement and barrier effects associated with the Proposed Development array during the operation and maintenance phase are considered in more detail below in the Project Alone: Population-Level Impacts section. This presents the outputs from PVAs of the potential effects of predicted displacement mortality on the SPA population.

Changes to prey availability

2008. Potential impacts on key prey species for guillemots breeding at the Buchan Ness to Collieston Coast SPA during the operation and maintenance phase have been assessed in volume 2, chapter 9 of the Offshore EIA Report using the appropriate maximum design scenarios for these receptors. Reduction or disruption to prey availability through temporary and long-term subtidal habitat loss/disturbance, increased SSC and deposition, reductions in water clarity, EMF from subsea electrical cabling, and colonisation of subsea structures, could affect guillemot survival and productivity in the Buchan Ness to Collieston Coast SPA population.
2009. The same evidence basis and context in relation to this effect pathway for the operation and maintenance phase applies to the Buchan Ness to Collieston Coast SPA guillemot population as to the St Abb’s Head to Fast Castle SPA guillemot population. This is detailed in the section on Project Alone: Operation and Maintenance – Changes to Prey Availability for the St Abb’s Head to Fast Castle SPA population.
2010. Given this, it is considered that there is relatively little potential for the Buchan Ness to Collieston Coast SPA guillemot 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 Buchan Ness to Collieston Coast SPA guillemot population.

Project alone: population-level impacts

2011. As determined above, the effects from the Proposed Development alone which could lead to an adverse effect on the Buchan Ness to Collieston Coast SPA guillemot population are limited to displacement (inclusive of barrier effects) during the operation and maintenance phase. For other effect pathways, there is considered to be no potential for an adverse effect on this population as a result of the Proposed Development alone, with any such effects likely to be small and of little, or no, consequence in terms of impacts at the population level.
2012. Given this, PVA was undertaken on the mortality to the adult and immature age classes predicted due to the displacement effects associated with the Proposed Development, as determined by both the Scoping and Developer Approaches (see Table 5.141 above). The population model for the SPA population was a stochastic, density independent, matrix model, based upon the demographic parameters specified in Table 2.9 of the Offshore EIA Report, volume 3, appendix 11.6. The starting population size was the 2019 count for the SPA, with the projected population trends considered over a 35 year timescale (Offshore EIA Report, volume 3, appendix 11.5). The approach and methods to undertaking the PVA are as described in the section on Project Alone: Population-Level Impacts for the St Abb’s to Fast Castle SPA kittiwake population above (with further details provided in the Offshore EIA Report, volume 3, appendix 11.6).
2013. Outputs from the PVA are summarised according to the median predicted population-sizes at the end of the projection period, and the three metrics which the Scoping Opinion (volume 3, appendix 6.2 of the Offshore EIA Report) advised should be used for the interpretation of outputs and which have been shown to have relatively low sensitivity to factors such as varying population status and the mis-specification of the demographic rates underpinning the population model (Cook and Robinson 2015, Jitlal et al., 2017). These metrics are:

• The CPS – the median of the ratio of the end-point size of the impacted to un-impacted (or baseline) population, expressed as a proportion;
• The CPGR - the median of the ratio of the annual growth rate of the impacted to un-impacted population, expressed as a proportion; and
• The centile of the un-impacted population that matches the median (i.e. 50th centile) of the impacted population (based upon the distribution of the end-point population-sizes generated by the multiple replications of the model runs, the value should always be less than 50 because the median for the impacted population is not expected to exceed that for the un-impacted population).

Table 5.142: Projected 35 Year Population Sizes and Associated PVA Metrics for the Buchan Ness to Collieston Coast SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development Alone

2014. The PVA predicted that the Buchan Ness to Collieston Coast SPA guillemot population would increase over the 35 year projection period irrespective of the effects from the Proposed Development. Thus, the population is predicted to be almost three times larger than the current estimate of 39,553 adult birds under all scenarios, including the baseline which assumes no wind farm effects (Table 5.142). Although the predicted increases in population size are inevitably greatest for the baseline scenario (because the PVAs are based on density independent models, which assume all mortality from the wind farm effects is additive and that there are no compensatory mechanisms operating within the population), the differences with the impact scenarios are small. Whilst the predicted levels of increase are unlikely to occur in reality (and are, in part, a consequence of the absence of any compensatory density dependence within the models – as discussed in the section on Project Alone: Population-level impacts for the St Abb’s Head to Fast Castle SPA kittiwake population), the prediction for an increasing trend is consistent with the documented, overall, long-term trend for this SPA population but not with the apparent stability in numbers since the mid-1990s (see above).
2015. The predicted population-level impacts are small, irrespective of whether these are determined using the Developer or Scoping Approaches. Thus, for the upper range of the Scoping Approach (i.e. Scoping Approach B), the CPS value indicates a reduction of approximately 2% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects (Table 5.142). The associated reduction in annual population growth rate (relative to that predicted under baseline conditions) is 0.1%, whilst the centile value of 46.4 indicates a considerable overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a high likelihood of the impacted population being of a similar size to the un-impacted population after 35 years. As would be expected, the metrics for the lower range of the Scoping Approach and the Developer Approach suggest even smaller levels of impact (Table 5.142).
2016. For the same reasons as described in the section on Project-Alone: Population-Level Impacts for the St Abb’s Head to Fast Castle SPA guillemot population, the assessment of the Buchan Ness to Collieston Coast SPA guillemot population incorporates high levels of precaution, which extend beyond the differences between the Developer and Scoping Approaches that are outlined above (and detailed in the Offshore EIA Report, volume 3, appendix 11.4). Notably, the concerns over the extent to which the seasonal mean peak abundances (which provide the basis for the displacement mortality estimates) are likely to be representative of the overall usage of the Proposed Development array and two kilometre buffer by guillemot are equally relevant to the Buchan Ness to Collieston Coast SPA population as to the St Abb’s Head to Fast Castle SPA population. The evidence available from tracking data suggests that levels of usage of the Proposed Development array area and two kilometre buffer during the breeding season by guillemots from the Buchan Ness to Collieston Coast SPA are likely to be low (Cleasby et al. 2018).

Project alone: conclusion

2017. It is considered that the predicted levels of impact from the Proposed Development alone on the Buchan Ness to Collieston Coast SPA guillemot population are of a small scale, as determined by both the Developer and Scoping Approaches. For both the Developer and Scoping Approaches it is also the case that the centile metric indicates a high likelihood of the impacted population being of similar size to the un-impacted population after 35 years. These levels of impact are within the context of an assessment which incorporates high levels of precaution (particularly as determined by the Scoping Approach) and a population for which the documented, long-term, trend is increasing but with stability over the more recent decades. Given this, it is concluded that the effects from the Proposed Development alone (as determined by either the Developer or Scoping Approaches) would not result in an adverse effect on this SPA population.

Effects in-combination

Effects of relevance to the in-combination assessment

2018. As detailed above, any effects from the Proposed Development alone on the Buchan Ness to Collieston Coast SPA guillemot population during construction and decommissioning and resulting from disturbance and changes to prey availability during operation and maintenance will be small and highly localised. As such, there is considered to be no potential for these effect pathways to add to impacts at the population-level that might result from other effects pathways associated with the Proposed Development or from the effects due to other plans and projects.
2019. Therefore, the potential for effects of the Proposed Development to act on the Buchan Ness to Collieston Coast SPA guillemot population in-combination with other plans and projects is limited to the displacement (inclusive of barrier effects) effect pathway during operation and maintenance. Following advice from NatureScot provided through the Ornithology Roadmap process (at meeting 3, 8th December 2021), the following sections consider these potential effects for (i) the Proposed Development in-combination with the other Forth and Tay wind farms and (ii) the Proposed Development in-combination with the other UK North Sea wind farms (noting that scenario (ii) includes those plans and projects which comprise scenario (i)).

Displacement/barrier effects – operation and maintenance

2020. As described in annex E of volume 3, appendix 11.6 of the Offshore EIA Report, estimates of displacement mortality during both the breeding and non-breeding periods which had been attributed to the Buchan Ness to Collieston Coast SPA guillemot population were extracted from the existing assessments for offshore wind farms that are in planning, consented, under construction or in operation. As for the potential displacement mortality estimated for the Proposed Development, the mortality attributed to the SPA population from other offshore wind farms was estimated using the SNCB matrix approach, with details on the displacement and mortality rates that had been applied being available in each case. Thus, it was possible to adjust the estimated mortalities from each of the other projects to align with the displacement and mortality rates on which the Scoping and Developer Approaches are based.
2021. The potential mortality estimates derived for the other projects were combined with those for the Proposed Development to give in-combination estimates for both the Forth and Tay wind farms and the UK North Sea wind farms according to both the Scoping Approach and Developer Approach. In addition to effects from the Forth and Tay wind farms, effects on the SPA population also were identified for the Kincardine, Hywind and Moray West wind farms (annex E of Offshore EIA Report, volume 3, appendix 11.6).

Table 5.143: Estimated Annual Mortality of Buchan Ness to Collieston Coast SPA Guillemots 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 Forth and Tay Wind Farms and other UK North Sea Wind Farms

2022. Incorporating the potential mortality predicted from the displacement effects associated with the other Forth and Tay wind farms leads to an increase of approximately 30 - 40% in the predicted displacement mortality compared to the Proposed Development alone for each of the Developer and Scoping Approaches, whilst for the other UK North Sea wind farms this increase (compared to the Proposed Development alone) is approximately 80 – 100% (Tables 5.141 and 5.143). The effects attributed to the breeding season account for approximately 40 – 65% of the predicted annual mortality for the Proposed Development in-combination with the other Forth and Tay wind farms and approximately 43 – 70% for the Proposed Development in-combination with the other UK North Sea wind farms (with this contribution being lowest for the Developer Approach and highest for the upper range of the Scoping Approach in each case – Table 5.143).
2023. For the Proposed Development in-combination with the other Forth and Tay wind farms, the additional annual mortality of adult guillemots from the Buchan Ness to Collieston Coast SPA population predicted due to displacement represents between 0.02% of the current adult breeding population at this colony (i.e. 39,553 individuals – Table 3.3 in the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and between 0.03 – 0.07% as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (based on applying a mortality rate of 0.073 – see Table 2.9 in the Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult displacement mortality equate to an increase of 0.2% for the Developer Approach and of 0.5 – 1.0% for the lower and upper estimates from the Scoping Approach.
2024. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult guillemots from the Buchan Ness to Collieston Coast SPA population predicted due to displacement represents between 0.02% of the current adult breeding population at this colony (i.e. 39,553 individuals – Table 3.3 in the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and between 0.05 – 0.10% as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (based on applying a mortality rate of 0.073 – see Table 2.9 in volume 3, appendix 11.6 of the Offshore EIA Report), the estimates of adult displacement mortality equate to an increase of 0.3% for the Developer Approach and of 0.7 – 1.4% for the lower and upper estimates from the Scoping Approach.
2025. The potential levels of impact on the Buchan Ness to Collieston Coast SPA guillemot population resulting from the predicted mortality from displacement and barrier effects associated with the Proposed Development in-combination with other wind farms in the Forth and Tay or in-combination with other wind farms in the UK North Sea during the operation and maintenance phase are considered in more detail below in the Effects In-Combination: Population-Level Impacts section. This presents the outputs from PVAs of the potential effects of predicted displacement mortality on the SPA population.

In-combination: population-level impacts

2026. As for the Proposed Development alone, PVA was undertaken on the mortality to the adult and immature age classes predicted due to the displacement effects associated with the Proposed Development in-combination with the other Forth and Tay wind farms and 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 5.143 above).
2027. The approach to the PVA and the metrics used to summarise the PVA outputs are as described for the Proposed Development alone (see Project Alone: Population-Level Impacts section above).

Table 5.144: Projected 35 Year Population Sizes and Associated PVA Metrics for the Buchan Ness to Collieston Coast SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development In-Combination with the other Forth and Tay Wind Farms

Table 5.145: Projected 35 Year Population Sizes and Associated PVA Metrics for the Buchan Ness to Collieston Coast SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development In-Combination with the other UK North Sea Wind Farms

2028. 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 either the other Forth and Tay wind farms or the other UK North Sea wind farms suggest greater population-level impacts than as predicted for the Proposed Development alone (compare Table 5.142 with Tables 5.144 and 5.145). However, the predicted levels of impact remain relatively small, irrespective of whether these are determined using the Developer or Scoping Approaches.
2029. Focussing on the Proposed Development in-combination with the other UK North Sea wind farms, the CPS values indicate that the SPA population size would be reduced by 1 - 4% after 35 years relative to that in the absence of any wind farm effects, as determined by the Developer and Scoping Approaches (Table 5.145). The associated reduction in annual population growth rate (relative to that predicted under baseline conditions) is 0.1% for the Scoping Approach and is not detectable for the Developer Approach (at least when the CPGR is expressed to three decimal places). The centile values range from 43.9 – 48.6, indicating a considerable overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a high likelihood of the impacted population being of a similar size to the un-impacted population after 35 years. The PVA metrics for the Proposed Development in-combination with the other Forth and Tay wind farms indicate lower levels of impact, as would be expected from the lower predicted mortalities (Table 5.144).

In-combination: conclusion

2030. On the basis of both the Developer and Scoping Approaches, the potential effects from the Proposed Development in-combination with the other Forth and Tay wind farms or the other UK North Sea wind farms on the Buchan Ness to Collieston Coast SPA guillemot population are predicted to be relatively small, with the resultant population-level impacts also predicted to be small. In addition, for both of these in-combination scenarios, the PVA metrics indicate a high likelihood of the population being of a similar size to that which would occur in the absence of the wind farm effects after 35 years. These levels of impact are considered within the context of the long-term increasing (and more recently stable) population trend and the ‘favourable maintained’ condition of the SPA population, as well as the high levels of precaution incorporated in the assessment (particularly as determined by the Scoping Approach).
2031. Given the above, it is concluded that the effects from the Proposed Development in-combination with other plans and projects would not result in an adverse effect on the Buchan Ness to Collieston Coast SPA guillemot population, with this conclusion being irrespective of whether the effects are determined by the Developer or Scoping Approaches.

Assessment for the breeding seabird assemblage

2032. The breeding seabird assemblage for the Buchan Ness to Collieston Coast 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 95,000 individual seabirds). Guillemot and kittiwake are amongst the species identified in the citation as having nationally important populations which contribute to the Buchan Ness to Collieston Coast SPA breeding seabird assemblage.
2033. Potential impacts of the Proposed Development alone and in-combination with either the other Forth and Tay wind farms or the 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 Proposed Development alone and in-combination with the other Forth and Tay wind farms, no potential for an adverse effect is identified in relation to the SPA populations of kittiwake or guillemot, as determined by either the Developer or Scoping Approaches. However, for the Proposed Development in-combination with the other UK North Sea wind farms the potential for an adverse effect is identified in relation to the SPA kittiwake population, as determined by the Scoping Approach but not as determined by the Developer Approach.
2034. The Buchan Ness to Collieston Coast SPA is currently two to two and half times larger than those at the St Abb’s Head to Fast Castle SPA and at the Forth Islands SPA. Therefore, despite the documented long-term decline in this population, it is not considered that the effects from the Proposed Development in-combination with the other UK North Sea wind farms (as determined by the Scoping Approach) are likely to lead to a risk of this population being lost from the breeding seabird assemblage at the Buchan Ness to Collieston Coast SPA (in contrast to the conclusions reached for the St Abb’s Head to Fast Castle SPA and Forth Islands SPA). Also, given the range of species present within the SPA seabird assemblage and their relative abundances, together with the predicted level of impact on the SPA kittiwake population, it is considered that this potential adverse effect on the SPA kittiwake population would not be sufficient to result in a subsequent adverse effect on the seabird assemblage.
2035. Therefore, it is concluded that there is no potential for an adverse effect on the breeding seabird assemblage feature of the Buchan Ness to Collieston Coast SPA either as a result of the effects from the Proposed Development alone or in-combination with other plans and projects. This conclusion is irrespective of whether the effects are determined by the Scoping or Developer Approach.

Site conclusion

Developer approach

2036. It is concluded that there is no potential for an adverse effect on the breeding seabird assemblage qualifying feature of the Buchan Ness to Collieston Coast SPA or on the named component species of this feature due to the effects from the Proposed Development alone or in-combination with other plans and projects. Consequently, it is concluded that there is no potential for an Adverse Effects on Integrity of the Buchan Ness to Collieston Coast SPA.

Scoping approach

2037. It is concluded that the possibility of an adverse effect cannot be discounted for the Buchan Ness to Collieston Coast SPA population of breeding kittiwake (noting this species is a named component of the seabird assemblage feature only). For the kittiwake population, the potential for an adverse effect arises from the Proposed Development in-combination with the other UK North Sea wind farms (but not from the Proposed Development alone or in-combination with the other Forth and Tay wind farms). The predicted impacts on the SPA kittiwake population are not considered to be sufficient to lead to a potential adverse effect on the breeding seabird assemblage feature.
2038. Consequently, it is concluded that an Adverse Effects on Integrity of the Buchan Ness to Collieston Coast SPA cannot be excluded due to effects of the Proposed Development in-combination with the other UK North Sea wind farms.

5.7.6.    Troup, Pennan and Lion’s Head SPA

European site information and conservation objectives

2039. The Troup, Pennan and Lion’s Heads SPA is a 9 km stretch of sea cliffs along the Aberdeenshire coast, situated approximately 135 km from the Proposed Development. The boundary of the SPA overlaps with the boundary of Gamrie and Pennan coast SSSI and the seaward extension extends approximately 2 km into the marine environment. The SPA was classified in 1997, with the marine extension classified in 2009.
2040. The site qualifies under Article 4.2 by regularly supporting two migratory seabird species and in excess of 20,000 breeding seabirds, including three named component species (Table 5.146). The potential for LSE has been identified in relation to three of these five species (Table 5.146), with the effect pathways associated with LSE for each of these detailed in Table 3.1 and set out in the assessment below.
2041. The conservation objectives of this SPA (as determined from NatureScot’s SiteLink (SiteLink (nature.scot)) 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
  2042. Further information on this European site is presented in appendix 3A.

Table 5.146: Details on the Qualifying Features of the Troup, Pennan and Lion’s Heads SPA

*Named components of the assemblage only.

Assessment for the kittiwake population

2043. The Troup, Pennan and Lion’s Head SPA kittiwake population is currently estimated to number 21,232 individuals, based upon the most recently available count data from 2017 (Offshore EIA Report, volume 3, appendix 11.5). This is substantially below the citation level (which is equivalent to 63,200 individuals - Table 5.146). Based on the data available on the SMP, the peak count is 63,328 individuals from 1995, which represented a substantial increase compared to the earliest available estimate of 33,188 individuals from 1986. However, since 1995 the population has undergone a progressive decline to its current level.

The potential for impacts on the kittiwake population

2044. The Proposed Development and two kilometre buffer around the Proposed Development array area7 do not overlap with the Troup, Pennan and Lion’s Head SPA, so that potential impacts on its kittiwake population will only arise as a result of individuals from the colony occurring in the area (or vicinity) of the Proposed Development. Consequently, the main focus of the assessment for this SPA population is concerned with the Conservation Objective to maintain, in the long term, the population of the species as a viable component of the site 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 first Conservation Objective (as for the maintain in the long term no significant disturbance of the species, because disturbance would only be considered significant if it caused an adverse effect on the population viability of the qualifying features).
2045. From published information on kittiwake foraging ranges generally (Woodward et al. 2019) and evidence from tracking data (Wakefield et al. 2017), it is apparent that during the breeding period kittiwakes from the Troup, Pennan and Lion’s Head SPA could occur within the area of the Proposed Development and of the two km buffer around the Proposed Development array. This is reflected in the findings of the apportioning exercise, which estimates that less than 1% of the kittiwakes occurring on the Proposed Development array area during the breeding season derive from this SPA colony (volume 3, appendix 11.5 of the Offshore EIA Report). The breeding period for kittiwake is defined as mid-April to August, following the NatureScot (2020) guidance.
2046. For the reasons described for the St Abb’s Head to Fast Castle SPA kittiwake population, during the non-breeding season there is likely to be the potential for kittiwake from the Troup, Pennan and Lion’s Head SPA 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, on the basis of applying the BDMPS defined periods within the context of the overall non-breeding period defined by NatureScot – Furness 2015, NatureScot 2020, Offshore EIA Report, volume 3, appendix 11.5). Given the above, the Proposed Development may have potential effects on the Troup, Pennan and Lion’s Head SPA kittiwake population during breeding and non-breeding periods.

Project alone: construction and decommissioning

Disturbance

2047. Direct disturbance to kittiwakes during the construction phase may arise within the Proposed Development array area (and its immediate vicinity) as a result of increased vessel movements and helicopter activity, as well as from other activities directly associated with the installation of the wind turbine foundations and other infrastructure, whilst there will also be increased vessel activity along the Proposed Development export cable corridor due to the cable laying activities. The levels of such activities that could arise are outlined in Table 4.1, with these activities occurring during construction campaigns within a construction period of at most eight years duration.
2048. A total of up to 11,482 vessel round trips may occur over the construction phase, whilst it is estimated that a maximum of 134 vessels could occur within the area of the Proposed Development at any one time (Table 4.1). However, this is within the context of high baseline levels of vessel traffic within this area (e.g. surveys recorded an average of 14 vessels per day within a 10 nm buffer around the Proposed Development over a 14-day period in August 2022, whilst also showing an average of three to four vessels intersecting the Proposed Development array area per day over summer - volume 2, chapter 13 of the Offshore EIA Report).
2049. When using the marine environment (and not at the breeding colony), kittiwakes are considered to have a relatively low sensitivity to such sources of direct disturbance. Thus, reviews of the sensitivity of different seabird species to disturbance from vessels and helicopter traffic assign kittiwake as ‘2’ on a five-scale ranking system, where 1 indicates hardly any or limited escape/avoidance behaviour and very short flight distance when approached and 5 indicates strong escape/avoidance behaviour and a large response distance (Garthe and Hüppop 2004, Furness et al. 2013).
2050. The total area to be affected by such disturbance over the full eight years of the construction phase also represents a small proportion of the total area of marine habitat available to kittiwakes from the Troup, Pennan and Lion’s Head SPA. Thus, the Proposed Development array area encompasses 1,010 km2, whilst the Proposed Development export cable corridor encompasses 168 km2. Together these areas represent less than 1% of the total breeding season foraging area that is potentially available to the SPA kittiwake population, as defined by the generic measure of the species’ mean maximum breeding season foraging range plus 1 SD (i.e.156.1±144.5 km - Woodward et al. 2019) and assuming that this range is represented by a semicircle to the seaward side of the colony. Similarly, the Proposed Development array and export cable corridor represent approximately 3% of the breeding season foraging area if considering the mean maximum foraging range only.
2051. Tracking data (and associated modelling of foraging distributions) for kittiwake suggest that the Proposed Development array area and Proposed Development export cable corridor are beyond waters that are heavily used by birds from the Troup, Pennan and Lion’s Head SPA during the breeding season (Cleasby et al. 2018).
2052. 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). Thus, the potential for effects of construction-related disturbance is generally lower than during the breeding season (but noting that in the case of the Troup, Pennan and Lion’s Head SPA, the distance of the SPA from the Proposed Development means that the likelihood of usage of the Proposed Development by the SPA birds during the breeding season is also low and, hence, any such seasonal effect will be less marked).
2053. In addition, it is important to consider that the construction activities will not occur simultaneously across the entirety of the Proposed Development array area or the Proposed Development export cable corridor but, rather, will be carried out in different areas at different times. Thus, the activities will be concentrated within discrete (often small) parts of these wider areas, and within such areas they will not extend over the full duration of the construction phase, so further reducing the potential to which birds may be subject to disturbance effects. For example, cable laying for the Proposed Development export cable will occur over a total of two years, whilst within the Proposed Development array area it is likely that construction activities would be confined largely to discrete areas at any one time.
2054. 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.
2055. Given the low sensitivity of kittiwake to disturbance effects, the large distance of the Proposed Development from the SPA (relative to the estimated kittiwake breeding season foraging range), the relatively small areas that will be subject to activities with the potential to result in disturbance at any given time during the construction period and the fact that these potential effects will be temporary, it is considered that there is no potential for construction or decommissioning related disturbance to lead to an adverse effect on the Troup, Pennan and Lion’s Head 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 (volume 2, chapter 11 of the Offshore EIA Report).

Displacement

2056. As detailed above, kittiwake is considered to have a low sensitivity to disturbance, whilst potential effects of disturbance during the construction and decommissioning phases will only extend across a small part of the wider foraging areas used by the Troup, Pennan and Lion’s Head SPA kittiwake population and be limited to, at most, an eight year period during construction (and a likely similar or shorter period during decommissioning). Furthermore, as detailed above, potential effects of disturbance will not occur simultaneously across the entirety of the Proposed Development array area or Proposed Development export cable corridor but, rather, will 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 kittiwakes from this SPA will be limited to relatively small areas, with the potential effects also being of a temporary nature.
2057. Therefore, based upon the above, it is considered that there is relatively little potential for the Troup, Pennan and Lion’s Head SPA kittiwake population to be affected by displacement during the construction or decommissioning phases, with any such effects only extending across relatively small areas and tending to be temporary in nature. Consequently, it is considered that there is no potential for construction or decommissioning related displacement to lead to an adverse effect on the Troup, Pennan and Lion’s Head 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-related displacement was required (volume 2, chapter 11 of the Offshore EIA Report).

Changes to prey availability

2058. Key prey species for kittiwakes include sandeel and sprat (del Hoyo et al., 1996). Indirect effects on kittiwakes may arise as a result of changes in the availability, distribution, or abundance of these species during the construction and decommissioning phases of the Proposed Development. Reduction or disruption to prey availability may cause displacement from foraging grounds or reduced energy intake, affecting survival rates or productivity in the Troup, Pennan and Lion’s Head SPA kittiwake population in the short-term.
2059. 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 Troup, Pennan and Lion’s Head 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. Additionally, the relatively large distance of the Proposed Development from the Troup, Pennan and Lion’s Head SPA is relevant because it reduces the likelihood that kittiwakes from this SPA will use the Proposed Development during the breeding season (volume 3, appendix 11.5 of the Offshore EIA Report).
2060. Given this, it is considered that there is relatively little potential for the Troup, Pennan and Lion’s Head 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 Troup, Pennan and Lion’s Head SPA kittiwake population.

Project alone: operation and maintenance

Disturbance

2061. 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 Troup, Pennan and Lion’s Head SPA. As described in the section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population, kittiwakes are considered to have a relatively low sensitivity to such sources of direct disturbance at sea (Garthe and Hüppop 2004, Furness et al., 2013).
2062. The maximum design scenario is for up to 3,393 vessel round trips per year over the operational lifetime of the project. Vessel types which will be required during the operation and maintenance phase include those used during routine inspections, repairs and replacement of equipment, major component replacement, painting or other coatings, removal of marine growth, replacement of access ladders, and geophysical surveys (Table 4.1).
2063. Based on information presented in the section on Project Alone: Operation and Maintenance – Disturbance for the St Abb’s Head to Fast Castle SPA kittiwake population and in the Offshore EIA Report, volume 2, chapter 13, baseline levels of vessel traffic in the Offshore Ornithology study area are relatively high. In the context of the baseline levels of vessel traffic across the Offshore Ornithology study area, the increase during the operation and maintenance phase is considered to be relatively small. Vessel movements will be within the Proposed Development array area and export cable corridor and will follow existing shipping routes to/from ports. In addition, Project Codes of Conduct included as a part of the NSVMP (Offshore EIA Report, volume 4, appendix 25) will be issued to all project vessel operators to avoid sudden changes in course or speed which will minimise the potential for disturbance. Within the Proposed Development array area, movements and associated maintenance activities will be restricted to individual wind turbines over a period of days to weeks.
2064. The size and noise outputs from vessels during the operation and maintenance phase will be similar to those used in the construction phase. However, the number of vessel return trips per year and their frequency will be much lower for the operation and maintenance phase compared to the construction phase. In addition, activities during the operation and maintenance phase will not occur simultaneously across the entirety of the Proposed Development array area and export cable corridor but intermittently within discrete (often very small) parts of these wider areas.
2065. Given the discrete areas relative to the species’ foraging range that will be subject intermittently to potential disturbance from vessel use and maintenance activities (Woodward et al., 2019), 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 Troup, Pennan and Lion’s Head SPA kittiwake population.

Displacement/barrier effects

2066. As outlined above, the SNCB matrix approach provides the basis for estimating displacement effects on seabird species in this assessment, with this approach assumed to also incorporate the impact of barrier effects within the estimates that are derived (SNCBs 2022, Offshore EIA Report, volume 3, appendix 11.4). Thus, throughout this section, mortality from displacement is assumed to refer to that which results from both displacement and barrier effects. The approach used to derive predicted levels of mortality 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 above (and in the Offshore EIA Report, volume 3, appendix 11.4).
2067. On the basis of the advice provided in the Scoping Opinion (volume 3, appendix 6.2 of the Offshore EIA Report), displacement effects on kittiwake are estimated for the breeding and non-breeding periods, with the latter separated into autumn and spring passage periods (Offshore EIA Report, volume 3, appendix 11.5). The displacement and associated mortality rates advised in the Scoping Opinion (subsequently termed the Scoping Approach) for kittiwake are:

• Breeding period: 30% displacement with lower and upper mortality rates of 1% and 3%.
• Non-breeding periods: 30% displacement with lower and upper mortality rates of 1% and 3%.
  2068. However, the approach to estimating kittiwake displacement effects advocated by the Scoping Opinion was considered overly precautionary in relation to the upper mortality rate used and the incorporation of mortality effects in the non-breeding periods, as detailed in volume 3, appendix 11.4, annex G of the Offshore EIA Report. In particular, it represented a marked change from the assumptions applied in assessments for other recent Scottish offshore wind farms (Marine Scotland 2017a,b,c) with no clear evidence apparently being available to justify such a change. Thus, based on a consideration of the available evidence for kittiwake displacement, the extent of the species’ ranging behaviour (particularly in the non-breeding periods), previous precedent and a need to incorporate precaution within the assessment, an alternative Developer Approach to estimating displacement effects was determined (volume 3, appendix 11.4, annex G of the Offshore EIA Report). The rates adopted by the Developer Approach are:
• Breeding period: 30% displacement with a mortality rate of 2%.
• Non-breeding periods: No measurable effects of displacement on mortality.
  2069. Estimates of kittiwake mortality were produced using the SNCB matrix on the basis of both the Scoping Approach and the Developer Approach (Offshore EIA Report, volume 3, appendix 11.4), with these estimates then apportioned to the Troup, Pennan and Lion’s Head SPA kittiwake population during the breeding and non-breeding periods according to the MS Apportioning Tool (Butler et al. 2020) and the BDMPS approach (Furness 2015), respectively (Offshore EIA Report, volume 3, appendix 11.5, Table 5.147). The resulting mortality estimates for the breeding period were apportioned to age classes on the basis of the plumage characteristics of kittiwakes recorded during the breeding period in the baseline surveys (Offshore EIA Report, volume 3, appendix 11.1), whilst for the non-breeding periods age classes were apportioned according to the stable age distributions of the population model used in Furness (2015). Based on advice provided by NatureScot and Marine Scotland Science following Roadmap Meeting 4 (G. Holland, email 26/01/2022), it was also assumed that 10% of the breeding adults in the SPA population miss breeding in any given year (i.e. sabbatical birds) so that the number of estimated adult deaths during the breeding season was adjusted accordingly.

Table 5.147: 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 Troup, Pennan and Lion’s Head SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals during the Breeding Season is also Presented

2070. Based upon the estimates and assumptions detailed above, the potential annual mortality amongst the SPA kittiwake population as a result of displacement is estimated as two adult and one immature birds based on the lower mortality rates for the Scoping Approach (i.e. Scoping Approach A) and as seven adult and three immature birds based upon the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B) (Table 5.148). The displacement effects predicted by the Scoping Approach are attributable mainly to the non-breeding season (which accounts for approximately 90% of the overall potential annual mortality – Table 5.148), reflecting the fact that this SPA is distant from the Proposed Development with a low likelihood of use by the SPA kittiwake population during the breeding season.
2071. The annual mortality from displacement as determined using the Developer Approach is predicted to be less than a single adult bird, which (in contrast to the estimates from the Scoping Approach) is entirely attributable to breeding season effects (on the basis that displacement effects on kittiwake during the non-breeding periods are not considered to result in detectable impacts on the population – volume3, appendix 11.4, annex G of the Offshore EIA Report).

Table 5.148: Estimated Potential Annual Mortality of Troup, Pennan and Lion’s Head 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

2072. The additional annual mortality of adult kittiwakes from the Troup, Pennan and Lion’s Head SPA population predicted due to displacement from the Proposed Development array represents considerably less than 0.01% of the current adult breeding population at this colony (i.e. 21,232 individuals – Table 3.3 in the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and of approximately 0.01 – 0.03% of this population as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.145 – see Table 2.13 in the Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult mortality equate to an increase of considerably less than 0.1% for the Developer Approach and of approximately 0.1 – 0.2% for the lower and upper estimates from the Scoping Approach.
2073. The potential levels of impact on the Troup, Pennan and Lion’s Head SPA kittiwake population resulting from the mortality predicted from displacement and barrier effects associated with the Proposed Development array during the operation and maintenance phase are considered in more detail 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.