Displacement
  1. 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 only extend across a small part of the wider foraging areas used by the St Abb’s Head to Fast Castle 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, with the potential effects also being of a temporary nature.
  2. Based upon the above, it is considered that there is relatively little potential for the St Abb’s Head to Fast Castle 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 St Abb’s to Fast Castle SPA guillemot population.
Changes to prey availability
  1. 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 St. Abb’s Head to Fast Castle SPA guillemot population in the short-term.
  2. During construction and decommissioning there are a number of ways in which effects on key prey species may occur including temporary subtidal habitat loss/disturbance, long-term subtidal habitat loss, increases in SSC and associated sediment deposition, underwater noise and vibration, and colonisation of subsea structures (see section on Project Alone: Construction and Decommissioning – Changes to prey availability for the SPA kittiwake population and volume 2, chapter 9 of the Offshore EIA Report). Increases in SSC and associated reductions in water clarity may also affect the ability of foraging guillemots to locate fish in the water column, thereby reducing prey availability.
  3. It is considered that foraging guillemots from the St. Abb’s Head to Fast Castle SPA will be largely unaffected by the low-level temporary increases in SSC, as the concentrations are likely to be within the range of natural variability (generally <5 mg/l but can increase to over 100 mg/l during storm events/increased wave heights) and will reduce to background concentrations within a very short period (approximately two tidal cycles). Furthermore, the Proposed Development array area and export cable corridor represent approximately 3% of the total breeding season foraging area that is potentially available to the SPA guillemot population, as defined by the species’ mean maximum breeding season foraging range plus 1 SD (i.e. 73.2±80.5 km; Woodward et al., 2019). As outlined in the section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population, modelling of guillemot foraging distributions indicates that the Proposed Development array area and export cable corridor have minimal overlap with waters that are predicted to be used by birds from the St Abb’s Head to Fast Castle SPA (Cleasby et al., 2018).
  4. During the non-breeding period, guillemot distribution is less constrained by the location of breeding colonies (Buckingham et al., 2022) but, following the scoping advice from NatureScot (volume 3, appendix 6.2 of the Offshore EIA Report) and subsequent correspondence (NatureScot email of 20th May 2022), it is assumed that the area occupied by the SPA population is defined by the mean maximum breeding season foraging range plus 1 SD. Thus, the potential for effects of construction and decommissioning-related changes to prey availability are assumed to be similar to those during the breeding season.
  5. Based upon the above, it is considered that there is relatively little potential for the St Abb’s Head to Fast Castle 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, and 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 St. Abb’s to Fast Castle SPA guillemot population. This conclusion is consistent with the outcome of the EIA which concluded that effects from changes in prey availability on guillemots during construction and decommissioning were not significant in EIA terms (volume 2, chapter 11 of the Offshore EIA Report).
Project alone: operation and maintenance
Disturbance
  1. Vessel use within the Proposed Development array area and export cable corridor during the operation and maintenance phase may lead to direct disturbance of guillemots from the St. Abb’s Head to Fast Castle SPA. As described in 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).
  2. 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).
  3. Based on information presented in the section on Project Alone: Operation and Maintenance – Disturbance for the 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.
  4. 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.
  5. 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 St Abb’s to Fast Castle SPA guillemot population. This conclusion is consistent with the outcome of the EIA which concluded that effects from disturbance on guillemots during construction and decommissioning were not significant in EIA terms (volume 2, chapter 11 of the Offshore EIA Report).
Displacement/barrier effects
  1. As outlined above, displacement effects on the St Abb’s Head to Fast Castle 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 for kittiwake above (and in Offshore EIA Report, volume 3, appendix 11.4).
  2. 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%.
    1. As with kittiwake, 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.
    2. 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%.
    1. 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 St Abb’s Head to Fast Castle 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 5.31). 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 St Abb’s Head to Fast Castle 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 5.31:
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 St Abb’s Head to Fast Castle SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals During The Breeding Season is Also Presented

Table 5.31: 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 St Abb’s Head to Fast Castle SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals During The Breeding Season is Also Presented

 

  1. 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 310 adult and 311 immature birds based on the lower mortality rates for the Scoping Approach (i.e. Scoping Approach A) and as 576 adult and 574 immature birds based upon the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B) (Table 5.32). The breeding season effects make the greatest contribution to these potential mortalities (comprising 86% and 77% of the total annual mortality for the lower and upper mortality rates, respectively) due to the larger mean peak population size, higher assumed mortality rates and higher proportion of birds assumed to derive from the SPA population (Table 5.32).
  2. The annual mortality from displacement as determined using the Developer Approach is predicted to be 111 adult and 110 immature birds, equating to approximately 35% and 20% of the mortality predicted for the lower and upper range of the Scoping Approach, respectively (Table 5.32). As for the Scoping Approach, effects during the breeding season make the greatest contribution (67%) to the predicted annual mortality, although this is less marked because the mortality rates for each seasonal period are assumed to be same under the Developer Approach.

 

Table 5.32:
Estimated Potential Annual Mortality of St Abb’s to Fast Castle 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

Table 5.32: Estimated Potential Annual Mortality of St Abb’s to Fast Castle 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

 

  1. The additional annual mortality of adult guillemot from the St Abb’s Head to Fast Castle SPA population predicted due to displacement from the Proposed Development Array represents 0.2% of the current adult breeding population at this colony (i.e. 61,408 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and between approximately 0.5 – 0.9% 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 volume 3, appendix 11.6 of the Offshore EIA Report), the estimates of adult mortality equate to an increase of 2.5% for the Developer Approach and of 6.9 – 12.9% for the lower and upper estimates from the Scoping Approach.
  2. The potential levels of impact on the St Abb’s Head to Fast Castle 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
  1. Potential impacts on key prey species for guillemots breeding at St. Abb’s Head to Fast Castle 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 St. Abb’s Head to Fast Castle SPA population.
  2. During the operation and maintenance phase, there is potential for temporary habitat loss/disturbance for up to 989,000 m2 as a result of the use of jack-up vessels during any component replacement activities and during any cable repair activities. These impacts will be similar to those identified for temporary habitat loss/disturbance the construction phase (as discussed in the section on Project Alone: Construction and Decommissioning – Changes to prey availability for the SPA population) and will be highly restricted to the immediate vicinity of these operations.
  3. As outlined in the section on Project Alone: Operation and Maintenance – Changes to prey availability for the SPA kittiwake population the presence of infrastructure within the Proposed Development, will result in long-term habitat loss of up to 7,798,856 m2 during the operation and maintenance phase. These areas of habitat loss will be discrete, either in the immediate vicinity of foundations, or relatively small isolated stretches of cable, representing a very low proportion of available habitat for key prey species (0.7% of the Proposed Development fish and shellfish ecology study area).
  4. Increased SSC could occur as a result of repair or remedial burial activities during the operation and maintenance phase, as outlined in the section on Project Alone: Operation and Maintenance – Changes to prey availability for the SPA kittiwake. The assessment in volume 2, chapter 9 of the Offshore EIA Report considered that any suspended sediments and associated deposition and water clarity reduction during operation and maintenance will be of the same magnitude, or lower, as for construction.
  5. The presence and operation of inter-array, interconnector and offshore export cables will result in emissions of localised EMF, however there is no evidence to suggest that the key prey species of auks (e.g. sandeel and clupeids) are electrosensitive and would respond to electrical and/or magnetic fields (volume 2, chapter 9 of the Offshore EIA Report).
  6. Artificial structures introduced to the marine environment provide hard substrate for settlement of various organisms, which can increase local food availability for higher trophic levels. Whilst there is mounting evidence of potential benefits of artificial structures in marine environment (Birchenough and Degrae 2020), the statistical significance of such benefits and details about trophic interactions, particularly in relation to key prey species for guillemot, remain largely unknown (Peschko et al., 2020; BOWL 2021a, 2021b; Scott, 2022). Overall, any change in prey abundance and/or distribution through the presence of subsea structures of foundations is likely to be small relative to the area over which breeding and non-breeding SPA guillemots forage.
  7. It is therefore considered that there is relatively little potential for the St Abb’s Head to Fast Castle 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 St. Abb’s to Fast Castle SPA guillemot population. This conclusion is consistent with the outcome of the EIA which concluded that effects from changes in prey availability on guillemots during operation and maintenance were not significant in EIA terms (volume 2, chapter 11 of the Offshore EIA Report).
Project alone: population-level impacts
  1. As determined above, the effects from the Proposed Development alone which could lead to an adverse effect on the St Abb’s Head to Fast Castle 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.
  2. 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 5.32 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 volume 3, appendix 11.6 of the Offshore EIA Report). The starting population size was the 2016 – 2018 count for the SPA, with the projected population trends considered over a 35 year timescale (volume 3, appendix 11.5). The approach and methods to undertaking the PVA are as described for kittiwake above (with further details provided in volume 3, appendix 11.6 of the Offshore EIA Report).
  3. 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:

 

Table 5.33:
Projected 35 Year Population Sizes and Associated PVA Metrics for the St Abb’s Head to Fast Castle SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development Alone

Table 5.33: Projected 35 Year Population Sizes and Associated PVA Metrics for the St Abb’s Head to Fast Castle SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development Alone

 

  1. The PVA predicted that the St Abb’s Head to Fast Castle 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 three times larger than the current estimate of 61,408 adult birds under baseline conditions (i.e. no wind farm effects) and twice its current size under the scenario of greatest annual mortality (i.e. Scoping Approach B) (Table 5.33). Given that 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 predicted increases are inevitably greatest for the baseline scenario and least for the scenario involving highest annual mortality (i.e. Scoping Approach B). Whilst the predicted levels of increase may be 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 SPA kittiwake population), the prediction for an increasing trend is broadly consistent with the documented, overall, long-term trend for this SPA population (Figure 5.15).
  2. The PVA metrics suggest marked differences in the predicted population-level impacts according to the Developer and Scoping Approaches. Thus, for the Developer Approach, the CPS value indicates that the displacement effects from the Proposed Development alone would result in a reduction of 7% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects (Table 5.33). The associated reduction in annual population growth rate (relative to that predicted under baseline conditions) is estimated to be 0.2%, whilst the centile value of 39.2 indicates a considerable overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a reasonable likelihood of the impacted population being of a similar size to the un-impacted population after 35 years.
  3. For the Scoping Approach, the CPS values indicate a reduction of 19 – 33% in population size after 35 years, relative to that in the absence of any wind farm effects (Table 5.33). The reduction in annual population growth rate (relative to that predicted under baseline conditions) is estimated to be 0.6 – 1.1%. The centile metric indicates little to, at most, moderate overlap in the distribution of the predicted impacted and un-impacted population sizes, suggesting at least a reasonably high likelihood of the impacted population being smaller than the un-impacted population after 35 years.
  4. As for the assessment of the St Abb’s Head to Fast Castle SPA kittiwake population, the assessment of the 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). Of particular relevance to the guillemot assessment is the reliance on the seasonal mean peak abundances for the prediction of displacement mortality. As would be expected these estimates are considerably higher than the equivalent seasonal mean values (by 44% and 64% for the breeding and non-breeding seasons, respectively – Offshore EIA Report, volume 3, appendix 11.4, annex B), whilst three of the four surveys that contribute to these mean peak values are from months which tend to be associated with pre-breeding concentrations or a pulse of post-breeding dispersal (i.e. March, April and September – see Table 3.3 in the displace tech rept). Thus, the seasonal mean peak values are unlikely to be representative of the usage of the Proposed Development array and two kilometre buffer by birds from nearby breeding colonies, and may grossly overestimate this. This is further supported by modelling of the foraging distributions of SPA guillemots (using data derived from tracking during the chick-rearing period) which indicates that the Proposed Development array area is well beyond core areas of usage (Cleasby et al. 2018).
  5. The reliance on PVAs which are based upon density independent population models is also likely to cause overestimation of the population-level impacts and give overly precautionary outputs, for the same reasons as outlined above for kittiwake.
Project alone: conclusion
  1. Based on the Developer Approach, the potential effects from the Proposed Development alone on the St Abb’s Head to Fast Castle SPA guillemot population are predicted to be relatively small, with the resultant population-level impacts also predicted to be small. In addition, the PVA metrics indicate a reasonably high chance of the population being of a similar size to that which would occur in the absence of the Proposed Development after 35 years. Given that the SPA population has shown an overall, long-term, increase in size and is considered to be in ‘favourable maintained’ condition, it is concluded that the effects from the Proposed Development alone would not result in an adverse effect on this population.
  2. The Scoping Approach predicts considerably greater effects from the Proposed Development alone, with the potential resultant population-level impacts being relatively large. These potential impacts are of a scale which would be considered likely to result in an adverse effect on the SPA population. However, as has been detailed above (and in Offshore EIA Report, volume 3, appendix 11.4), it is considered that the level of effects on guillemots assumed by the Scoping Approach are overly precautionary and without any reasonable basis or support from the available evidence. The potential for gross overestimation of the population-level impacts is further exacerbated by other precautionary elements of the assessment, which have been incorporated irrespective of the Developer or Scoping Approaches. Given this, it is considered that greater weight should be given to the conclusions as determined by the Developer Approach, which concluded no adverse effect on the St Abb’s Head to Fast Castle SPA guillemot population as a result of the Proposed Development alone.
Effects in-combination
Effects of relevance to the in-combination assessment
  1. As detailed above, any effects from the Proposed Development alone on the St Abb’s Head to Fast Castle 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.
  2. Therefore, the potential for effects of the Proposed Development to act on the St Abb’s Head to Fast Castle 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
  1. As described in annex D of Offshore EIA Report, volume 3, appendix 11.6, estimates of displacement mortality during both the breeding and non-breeding periods which had been attributed to the St Abb’s Head to Fast Castle 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 (Table 5.34), 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.
  2. 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. However, the potential effects on the SPA population were limited to the other Forth and Tay wind farms, noting that apportioning of the non-breeding season effects for guillemot did not rely on the BDMPS approach (as stated above, see also Offshore EIA Report, volume 3, appendix 11.5). Given that these two different in-combination scenarios are equivalent, the predicted effects are reported solely for the UK North Sea wind farms in the tables below (Table 5.34).

 

Table 5.34:
Estimated Annual Mortality of St. Abb's Head to Fast Castle 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 the other UK North Sea Wind Farms

Table 5.34: Estimated Annual Mortality of St. Abb's Head to Fast Castle 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 the other UK North Sea Wind Farms

1The Forth and Tay and UK North Sea in-combination effects for the SPA population are equivalent (so that they are reported for the latter scenario only).

 

  1. Incorporating the potential mortality resulting from the predicted displacement effects associated with the other UK North Sea wind farms increases the predicted displacement mortality of adult birds by approximately 20% compared to the Proposed Development alone for each of the Developer and Scoping Approaches (Tables 5.32 and 5.35).
  2. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult guillemots from the St Abb’s Head to Fast Castle SPA population predicted due to displacement represents between 0.2% of the current adult breeding population at this colony (i.e. 61,408 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and between 0.6 – 1.1% 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 3.0% for the Developer Approach and of 8.3 – 15.5% for the lower and upper estimates from the Scoping Approach.
  3. The potential levels of impact on the St Abb’s Head to Fast Castle 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 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
  1. 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 UK North Sea wind farms, as determined by both the Scoping and Developer Approaches (Table 5.35). 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 5.35:
Projected 35 Year Population Sizes and Associated PVA Metrics for the St Abb’s Head to Fast Castle SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development In-Combination with the Other UK North Sea Wind Farms

Table 5.35: Projected 35 Year Population Sizes and Associated PVA Metrics for the St Abb’s Head to Fast Castle SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development In-Combination with the Other UK North Sea Wind Farms

 

  1. 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 the other UK North Sea wind farms suggest greater population-level impacts than as predicted for the Proposed Development alone (compare Table 5.32 with Table 5.35). However, the values of the metrics used to quantify the population-level impacts do not represent a marked increase in the impacts compared to those for the Proposed Development alone. Thus, the PVA metrics for the Proposed Development in-combination with the other UK North Sea wind farms indicate slightly greater levels of impact than as described above for the Proposed Development alone.
  2. As explained above, the assessment for the Proposed Development in-combination with the other Forth and Tay wind farms is equivalent to that for the Proposed Development in-combination with the other UK North Sea wind farms in the case of this SPA population.
In-Combination: Conclusion
  1. On the basis of the Developer Approach, it is considered that the potential effects from the Proposed Development in-combination with the other UK North Sea wind farms would not result in an adverse effect on the St Abb’s Head to Fast Castle SPA guillemot population. The population-level impacts predicted to arise from these in-combination effects represent a small increase to those predicted due to the Proposed Development alone. As such, it is considered that the conclusions reached in relation to the Proposed Development alone are also valid for the in-combination scenario.
  2. For the Scoping Approach, the conclusions for the Proposed Development alone also apply to the Proposed Development in-combination with the other UK North Sea wind farms, with the predicted population-level impacts being of a scale considered likely to result in an adverse effect on the SPA population. However, the concerns highlighted in the Project Alone conclusions section over the Scoping Approach and its basis are considered to apply equally to the conclusions for the in-combination assessment.
  3. The above conclusions in relation to the Proposed Development in-combination with the other UK North Sea wind farms are also taken to apply to the Proposed Development in-combination with the other Forth and Tay wind farms (given that the two scenarios are equivalent for this SPA population).

Assessment for the razorbill population

  1. The St Abb’s Head to Fast Castle SPA razorbill population has shown an overall increase during the last 30 years or so, and relative stability since the late 1990s, based on count data from the St Abb’s Head NNR (which holds the vast majority of the SPA population – Figure 5.16). The population size has remained above the citation population size (2,180 individuals) since designation.

Figure 516:
Razorbill Population Trend at the St Abb’s Head NNR Between 1986 and 2018, With Two Counts For The Entire St Abb’s Head to Fast Castle SPA Also Shown (noting that the Latest SPA Count Is Shown for 2017 Because It Spans The Period 2016 – 2018). The Red Line Shows the Citation Population Size for the SPA (2,180 Individuals)13. Data are from The Seabird Monitoring Programme Database (Seabird Monitoring Programme | JNCC (bto.org))

Figure 516: Razorbill Population Trend at the St Abb’s Head NNR Between 1986 and 2018, With Two Counts For The Entire St Abb’s Head to Fast Castle SPA Also Shown (noting that the Latest SPA Count Is Shown for 2017 Because It Spans The Period 2016 – 2018). The Red Line Shows the Citation Population Size for the SPA (2,180 Individuals)13. Data are from The Seabird Monitoring Programme Database (Seabird Monitoring Programme | JNCC (bto.org))

The potential for impacts on the razorbill population
  1. The Proposed Development and two kilometre buffer around the Proposed Development array area7 do not overlap with the St Abb’s Head to Fast Castle SPA, so that potential impacts on its razorbill population will only occur 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).
  2. From published information on razorbill foraging ranges generally (Woodward et al. 2019) and tracking from the SPA specifically (Wakefield et al. 2017), it is highly likely that during the breeding period razorbill from the St Abb’s Head to Fast Castle SPA occur within the area of the Proposed Development and of the two km buffer around the Proposed Development array area. This is supported by the findings of the apportioning exercise, which estimates that approximately 23% of the razorbill occurring on the Proposed Development Array area during the breeding season derive from this SPA colony (Offshore EIA Report, volume 3, appendix 11.5). The breeding period for razorbill is defined as April to mid-August, following the NatureScot (2020) guidance.
  3. Based on the NatureScot scoping advice (volume 3, appendix 6.2 of the Offshore EIA Report), which draws upon the findings from Buckingham et al. (2022), razorbills are assumed to disperse more widely than guillemots during the non-breeding period, with their distribution concentrated in central areas of the North Sea during the mid-winter period. Consequently, it is assumed (for the purposes of the assessment) that during the non-breeding period birds from the St Abb’s Head to Fast Castle SPA population have the potential to occur within offshore wind farms throughout the UK North Sea waters during the autumn and spring passage periods and in mid-winter (defined as mid-August to October, January to March and November to December, 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 this, the Proposed Development may have potential effects on the St Abb’s Head to Fast Castle SPA razorbill population during breeding and non-breeding periods.
Project alone: construction and decommissioning
Disturbance
  1. As described for kittiwake, direct disturbance to razorbills during the construction phase may arise within the Proposed Development array area (and it’s 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.
  2. 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 - Offshore EIA Report, volume 2, chapter 13).
  3. When using the marine environment (and not at the breeding colony), razorbills are considered to have a moderate sensitivity to such sources of direct disturbance. Thus, reviews of the sensitivity of different seabird species to disturbance from vessels and helicopter traffic assign razorbill as ‘3’ 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).
  4. 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 razorbills from the St Abb’s Head to Fast Castle SPA. Thus, the Proposed Development array area encompasses 1,010 km2, whilst the Proposed Development export cable encompasses 168 km2. Together these areas represent approximately 3% of the total breeding season foraging area that is potentially available to the SPA razorbill population, as defined by the generic measure of the species’ mean maximum breeding season foraging range plus 1 SD (i.e. 88.7±75.9 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 area and export cable corridor represent approximately 10% of the breeding season foraging area if considering the mean maximum foraging range only. Modelling of razorbill foraging distributions, as derived from tracking data from the chick-rearing period, indicates that the Proposed Development array area has minimal overlap with waters that are predicted to be used by birds from the St Abb’s Head to Fast Castle SPA and although much of the length of the Proposed Development export cable corridor transits such areas, the overall area of overlap is small (Cleasby et al. 2018).
  5. During the non-breeding periods, razorbill distribution is not constrained by the location of the breeding colonies and birds from the SPA population are likely to occur across large parts of the North Sea (Furness 2015, Buckingham et al. 2022) so that the potential for effects of construction-related disturbance is lower than during the breeding season.
  6. In addition to the above, 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.
  7. 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.
  8. Given the moderate sensitivity of razorbill to disturbance effects, 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 St Abb’s to Fast Castle SPA razorbill population.
Displacement
  1. As detailed above, razorbill is considered to have a moderate 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 St Abb’s Head to Fast Castle SPA razorbill 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 razorbills from this SPA will be limited to relatively small areas, with the potential effects also being of a temporary nature.
  2. Based upon the above, it is considered that there is relatively little potential for the St Abb’s Head to Fast Castle SPA razorbill 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 St Abb’s to Fast Castle SPA razorbill population.
Changes to prey availability
  1. Sandeels are key prey for razorbills, with a range of other species taken including sprat and juvenile herring (del Hoyo et al., 1996). Indirect effects on razorbills 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 St. Abb’s Head to Fast Castle SPA razorbill population in the short-term.
  2. During construction and decommissioning there are a number of ways in which effects on key prey species may occur including temporary subtidal habitat loss/disturbance, long-term subtidal habitat loss, increases in SSC and associated sediment deposition, underwater noise and vibration, and colonisation of subsea structures (see the section on Project Alone: Construction and Decommissioning – Changes to prey availability for the SPA kittiwake population and volume 2, chapter 9 of the Offshore EIA Report). Increases in SSC and associated reductions in water clarity may also affect the ability of foraging razorbills to locate fish in the water column, thereby reducing prey availability.
  3. It is considered that foraging razorbills from the St. Abb’s Head to Fast Castle SPA will be largely unaffected by the low-level temporary increases in SSC, as the concentrations are likely to be within the range of natural variability (generally <5 mg/l but can increase to over 100 mg/l during storm events/increased wave heights) and will reduce to background concentrations within a very short period (approximately two tidal cycles). Furthermore, the Proposed Development array area and export cable corridor represent approximately 3% of the total breeding season foraging area that is potentially available to the SPA razorbill population, as defined by the species’ mean maximum breeding season foraging range plus 1 SD (i.e. 88.7±75.9 km; Woodward et al., 2019) and assuming that this range is represented by a semicircle to the seaward side of the colony. As outlined in the section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population, modelling of razorbill foraging distributions indicates that the Proposed Development array area has minimal overlap with waters that are predicted to be used by birds from the St Abb’s Head to Fast Castle SPA and although much of the length of the Proposed Development export cable corridor transits such areas, the overall area of overlap is small (Cleasby et al., 2018). Non-breeding season effects are considered to be lower than during the breeding season given that birds are no longer constrained by the location of their colonies and birds are likely to occur over larger parts of the North Sea (Furness 2015; Buckingham et al., 2022).
  4. Based upon the above, it is considered that there is relatively little potential for the St Abb’s Head to Fast Castle SPA razorbill 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 St. Abb’s to Fast Castle SPA razorbill population. This conclusion is consistent with the outcome of the EIA which concluded that effects from changes in prey availability on razorbills during construction and decommissioning were not significant in EIA terms (volume 2, chapter 11 of the Offshore EIA Report).
Project alone: operation and maintenance
Disturbance
  1. 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 razorbills from St. Abb’s Head to Fast Castle SPA. As described in the section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population, razorbills are considered to have a moderate sensitivity to such sources of direct disturbance at sea (Garthe and Hüppop 2004, Furness et al., 2013).
  2. 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).
  3. Based on information presented in the section on Project Alone: Operation and Maintenance – Disturbance for the SPA kittiwake population and in 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.
  4. 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.
  5. 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 St Abb’s to Fast Castle SPA razorbill population. This conclusion is consistent with the outcome of the EIA which concluded that effects from disturbance on razorbills during construction and decommissioning were not significant in EIA terms (volume 2, chapter 11 of the Offshore EIA Report).
Displacement/barrier effects
  1. As outlined above, displacement effects on the St Abb’s Head to Fast Castle SPA razorbill 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 for kittiwake above (and in the Offshore EIA Report, volume 3, appendix 11.4).
  2. On the basis of the advice provided in the Scoping Opinion (volume 3, appendix 6.2 of the Offshore EIA Report), displacement effects on razorbill 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 razorbill are:

 

Table 5.36:
The Mean Peak Abundance Estimates of Razorbill 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 St Abb’s Head to Fast Castle SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals During The Breeding Season is also Presented

Table 5.36: The Mean Peak Abundance Estimates of Razorbill 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 St Abb’s Head to Fast Castle SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals During The Breeding Season is also Presented

 

  1. Based upon the estimates and assumptions detailed above, the potential annual mortality amongst the SPA razorbill population as a result of displacement is estimated as 8 adult and 9 immature birds based on the lower mortality rates for the Scoping Approach (i.e. Scoping Approach A) and as 14 adult and 15 immature birds based upon the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B) (Table 5.37). The breeding season effects make the greatest contribution to these potential mortalities (comprising 95% and 92% of the total annual mortality for the lower and upper mortality rates, respectively) due to the higher assumed mortality rates and higher proportion of birds assumed to derive from the SPA population during this period (Table 5.37).
  2. The annual mortality from displacement as determined using the Developer Approach is predicted to be 3 adult and 3 immature birds, equating to approximately 31% and 18% of the mortality predicted for the lower and upper range of the Scoping Approach, respectively (Table 5.37). As for the Scoping Approach, effects during the breeding season make the greatest contribution (88%) to the predicted annual mortality, with this being slightly less marked because the mortality rates for each seasonal period are assumed to be same under the Developer Approach.

 

Table 5.37:
Estimated Potential Annual Mortality of St. Abb’s Head to Fast Castle SPA Razorbills as a Result of Displacement from The Proposed Development Array Area and 2 km Buffer as Determined by The Scoping Approach and Developer Approach

Table 5.37: Estimated Potential Annual Mortality of St. Abb’s Head to Fast Castle SPA Razorbills as a Result of Displacement from The Proposed Development Array Area and 2 km Buffer as Determined by The Scoping Approach and Developer Approach

 

  1. The additional annual mortality of adult razorbill from the St Abb’s Head to Fast Castle SPA population predicted due to displacement from the Proposed Development Array represents 0.07% of the current adult breeding population at this colony (i.e. 3,928 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and between approximately 0.2 – 0.4% 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 0.090 – see Table 2.19 in Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult mortality equate to an increase of 0.7% for the Developer Approach and of 2.3 – 4.0% for the lower and upper estimates from the Scoping Approach.
  2. The potential levels of impact on the St Abb’s Head to Fast Castle SPA razorbill 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.