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 kittiwakes from East Caithness Cliffs SPA for the reasons given in the section on Project Alone: Operation and Maintenance – Disturbance for the St. Abb’s Head to Fast Castle SPA kittiwake population.
  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   Open ▸ ).
  3. Based on information presented in the 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 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 operational and maintenance phase will not occur simultaneously across the entirety of the Proposed Development array area and offshore 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 East Caithness Cliffs SPA kittiwake population.
Displacement/Barrier Effects
  1. For the reasons given in Table 2.1   Open ▸ and Section 5.4, 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 Offshore EIA Report, volume 3, appendix 11.4 and in the section on Project Alone: Operation and Maintenance – Displacement/Barrier Effects for the St Abb’s Head to Fast Castle SPA kittiwake population.
  2. On the basis of the advice provided in the Scoping Opinion ( Table 2.1   Open ▸ ), 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%.
    1. 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 the Offshore EIA Report, volume 3, appendix 11.4, annex G. 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.
    2. 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 (Offshore EIA Report, volume 3, appendix 11.4, annex G). The rates adopted for kittiwake 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.
    1. 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 East Caithness Cliffs 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). 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, 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 5.165:
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 East Caithness Cliffs SPA population in each period. The proportion of adults assumed to be sabbaticals during the breeding season is also presented.

Table 5.165: 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 East Caithness Cliffs SPA population in each period. The proportion of adults assumed to be sabbaticals during the breeding season is also presented.

 

Table 5.166:
Estimated potential annual mortality of East Caithness Cliffs 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.

Table 5.166: Estimated potential annual mortality of East Caithness Cliffs 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.

  1. 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 5.2 adult and 2.6 immature birds based on the lower mortality rates of Scoping Approach A, and 15.6 adult and 7.7 immature birds based upon the higher mortality rates of Scoping Approach B ( Table 5.166   Open ▸ ). The displacement effects predicted by the Scoping Approach are largely attributable to the non-breeding season (with the potential non-breeding season mortality accounting for >99% of the overall annual mortality – Table 5.166   Open ▸ ).
  2. The annual mortality from displacement as determined using the Developer Approach is predicted to be 0.1 adult bird which is attributable to the breeding season, on the basis that displacement effects on kittiwake during the non-breeding periods are considered unlikely to result in detectable impacts on the population (Offshore EIA, volume 3, appendix 11.4, annex G).
  3. The additional annual mortality of adult kittiwakes from the East Caithness Cliffs SPA population predicted due to displacement from the Proposed Development represents 0.0002% of the current adult breeding population at this colony (i.e. 48,920 individuals – Table 3.3 of the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and between 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 0.146 – see Table 2.13 in the Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult mortality equate to an increase of 0.001% for the Developer Approach and of 0.07 – 0.22% for the lower and upper estimates from the Scoping Approach.
  4. The potential levels of impact on the East Caithness Cliffs SPA kittiwake population resulting from the mortality predicted from displacement/barrier effects associated with the Proposed Development array area during the operation and maintenance phase are considered in further below in the Project Alone: Population-Level Impacts section. This presents the outputs from PVAs of the combined effects of predicted displacement and collision mortality on the SPA population.
Collision Risk
  1. Predictions of the number of kittiwakes at risk from collisions due to the Proposed Development were calculated using the deterministic version of the SOSS offshore collision risk model (Band 2012, Offshore EIA Report, volume 3, appendix 11.3). Following the Scoping Opinion ( Table 2.1   Open ▸ ), the assessment is based on option 2 of the CRM, which uses the generic flight height data from Johnston et al., (2014a,b) and assumes a uniform distribution of flight heights across the rotor swept zone (as opposed to using the modelled flight height distribution; Band 2012). An avoidance rate of 98.9% was applied to these CRM outputs, as recommended for kittiwake (SNCBs 2014) and as advised by the Scoping Opinion.
  2. Guidance on the use of the CRM suggests that model predictions should be based upon the mean monthly densities of flying birds estimated within the array area (Band 2012) and, to the best of the Applicant’s knowledge, this approach has been applied in all recent UK offshore wind farm assessments. Despite this, the Scoping Opinion advised that the CRMs for the Proposed Development should use the maximum monthly densities of flying birds within the Proposed Development array area. Further details on these approaches are provided above in the Project Alone: Operation and Maintenance - Collision Risk section for the St Abb’s Head to Fast Castle SPA kittiwakes and in the Offshore EIA Report, volume 3, appendix 11.3. The CRMs for East Caithness Cliffs SPA kittiwakes were therefore undertaken following:

 

Table 5.167:
Predicted collision effects from the Proposed Development on the East Caithness Cliffs SPA kittiwake population, as determined by the Scoping Approach and Developer Approach. Estimates are for the worst-case design and are based on option 2 of the deterministic CRM using a 98.9% avoidance rate (see text).

Table 5.167: Predicted collision effects from the Proposed Development on the East Caithness Cliffs SPA kittiwake population, as determined by the Scoping Approach and Developer Approach. Estimates are for the worst-case design and are based on option 2 of the deterministic CRM using a 98.9% avoidance rate (see text).

  1. Based upon option 2 of the deterministic CRM with a 98.9% avoidance rate applied, and in conjunction with the estimates and assumptions detailed above, the annual collision mortality of kittiwakes from the East Caithness Cliffs SPA is predicted to be approximately 25.5 adults and 12.6 immatures as determined by the Scoping Approach, and approximately 18.4 adults and 8.9 immatures as determined by the Developer Approach ( Table 5.167   Open ▸ ). As for displacement, the vast majority of this mortality (i.e. >98%) is predicted to occur during the non-breeding season.
  2. The additional annual mortality of adult kittiwakes from the East Caithness Cliffs SPA population predicted due to collisions with turbines in the Proposed Development array area represents approximately 0.04% of the number of adults currently estimated to breed at this colony (i.e. 48,920 individuals – Table 3.3 of the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach and approximately 0.05% as determined by the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.146 – see Table 2.13 in the Offshore EIA Report, volume 3, appendix 11.6), the predicted adult collision mortality equates to increases of 0.26% and 0.36% for the Developer and Scoping Approaches, respectively.
  3. Using the collision estimates derived from the site-specific flight height data or from the stochastic CRM with avoidance rates as calculated for the bird collision-avoidance study (Bowgen and Cook 2018) would result in predicted collision mortalities on the East Caithness Cliffs SPA kittiwake population that are at least 50% lower than those presented in Table 5.167   Open ▸ above (upon which the assessment is based).
  4. More detailed consideration of the potential population-level impacts associated with the predicted collision mortalities in As for predicted displacement effects, kittiwake collision estimates are calculated 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). Estimates were apportioned to the East Caithness Cliffs SPA 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). The age class proportions and assumptions on sabbatical rates are also as detailed above in relation to displacement effects (Table 5.165).

 

  1. Table 5.167   Open ▸ is undertaken below in the Project Alone: Population-Level Impacts section, which presents the outputs from PVAs of the combined effects of predicted displacement and collision mortality on the SPA population.
Changes to Prey Availability
  1. Potential impacts on key prey species for kittiwakes breeding at the East Caithness Cliffs SPA during the operational 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, EMF from subsea electrical cabling, and colonisation of subsea structures, could affect kittiwake survival and productivity in the East Caithness Cliffs SPA kittiwake population.
  2. The same evidence basis and context in relation to this effect pathway for the operation and maintenance phase applies to the East Caithness Cliffs SPA kittiwake population as to the St Abb’s Head to Fast Castle SPA kittiwake 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.
  3. Given this, it is considered that there is relatively little potential for the East Caithness Cliffs SPA kittiwake population to be affected by changes to prey availability during the operation and maintenance phase, with any such effects being largely intermittent across a relatively small spatial extent. Consequently, it is considered that there is no potential for operational or maintenance related changes in prey availability to lead to an adverse effect on the East Caithness Cliffs SPA kittiwake population.
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 East Caithness Cliffs SPA kittiwake population are displacement/barrier effects and collision mortality 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 combined displacement and collision effects associated with the Proposed Development, as determined by both the Scoping and Developer Approaches (see Table 5.166   Open ▸ and Table 5.167   Open ▸ above). The population model for the SPA population was a stochastic, density independent, matrix model, based upon the demographic parameters specified in Table 2.13 of Offshore EIA Report, volume 3, appendix 11.6. The starting population size was the 2015 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 St Abb’s Head to Fast Castle SPA kittiwake population above, with further details provided in the Offshore EIA Report, volume 3, appendix 11.6).
  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:
  • 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 5.168:
Projected 35-year population sizes and associated PVA metrics for the East Caithness Cliffs SPA kittiwake population under different impact scenarios for the Proposed Development alone.

Table 5.168: Projected 35-year population sizes and associated PVA metrics for the East Caithness Cliffs SPA kittiwake population under different impact scenarios for the Proposed Development alone.

  1. The PVA predicted a population increase for the East Caithness Cliffs SPA kittiwake population, irrespective of the effects from the Proposed Development. Thus, the population is predicted to be 1.5 times larger than the current estimate of 48,920 breeding adults under all scenarios, including baseline which assumes no wind farm effects ( Table 5.168   Open ▸ ). Although the predicted increases 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 various impact scenarios are small.
  2. The predicted population-level impacts are small, irrespective of whether these are determined using the Developer or Scoping Approaches. Thus, for Scoping Approach B the CPS value indicates that the combined collision and displacement mortality associated with the Proposed Development alone would result in a reduction of approximately 2.7% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects ( Table 5.168   Open ▸ ). The associated reduction in annual population growth rate (relative to that predicted under baseline conditions) is estimated to be 0.1%, whilst the centile value of 47.8 indicates a considerable overlap in the distributions of the predicted impacted and unimpacted population sizes and, hence, a high likelihood of the impacted population being of a similar size to the unimpacted population after 35 years. As would be expected, the metrics for Scoping Approach A and the Developer Approach suggest even smaller levels of impact ( Table 5.168   Open ▸ ).
Project Alone: Conclusion
  1. Overall, it is considered that the predicted levels of impact from the Proposed Development alone on the East Caithness Cliffs SPA kittiwake population are of a relatively small scale. 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 unimpacted population after 35 years. Given this, it is concluded that the effects from the Proposed Development alone would not result in an adverse effect on this SPA population.
Effects In-Combination
Effects of relevance to the in-combination assessment
  1. For the same reasons as described in Effects In-Combination for the St. Abb’s Head to Fast Castle SPA kittiwake population, any effects from the Proposed Development alone on the East Caithness Cliffs SPA kittiwake 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 East Caithness Cliffs SPA kittiwake population in-combination with other plans and projects is limited to the displacement (inclusive of barrier effects) and collision risk effect pathways during operation and maintenance. The following sections consider these potential effects for the Proposed Development in-combination with the offshore wind farms in the UK North Sea.
Displacement/Barrier Effects – Operation and Maintenance
  1. As described in Offshore EIA report, volume 3, appendix 11.6, annex E, estimates of breeding season displacement mortality which had been attributed to the East Caithness Cliffs SPA kittiwake 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 5.166   Open ▸ ), 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. No displacement mortality estimates from other projects were available for kittiwake (for any SPA population) during the non-breeding periods because such effects have not been considered important in previous assessments for offshore wind farms in Scotland or England. Therefore, relevant seasonal mean peak abundance estimates of kittiwake were extracted from the baseline data from the assessments for other projects in the UK North Sea waters (Offshore EIA Report, volume 3, appendix 11.6, annex E), with the in-combination estimates derived according to the Scoping and Developer Approaches as described in the section on the In-Combination Displacement / Barrier Effects – Operation and Maintenance for the St Abb’s Head to Fast Castle SPA kittiwake population.
  3. The potential mortality estimates derived for the other projects were combined with those for the Proposed Development to give in-combination estimates according to both the Scoping Approach and Developer Approach ( Table 5.169   Open ▸ ).
Table 5.169:
Estimated annual mortality of East Caithness Cliffs SPA kittiwakes as a result of displacement from the Proposed Development array area and 2 km buffer as determined by the Scoping Approach and Developer Approach, in-combination with other UK North Sea wind farms.

Table 5.169: Estimated annual mortality of East Caithness Cliffs SPA kittiwakes as a result of displacement from the Proposed Development array area and 2 km buffer as determined by the Scoping Approach and Developer Approach, in-combination with other UK North Sea wind farms.

  1. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult kittiwakes from the East Caithness Cliffs SPA population predicted due to displacement represents 0.12 – 0.36% of the current adult breeding population at this colony (i.e. 48,920 individuals – Table 3.3 of volume 3, appendix 11.5) as determined by Scoping Approach A and B. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.146 – see Table 2.13 in volume 3, appendix 11.6), the estimates of adult displacement mortality equate to an increase of 0.8 – 2.5% for the lower and upper estimates from the Scoping Approach. For the Developer Approach, the additional annual mortality represents 0.13% of the current adult breeding population at East Caithness Cliffs SPA, representing a 0.9% increase in baseline annual mortality.
  2.  The potential levels of impact on the East Caithness Cliffs SPA kittiwake population resulting from the mortality predicted 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 combined effects of predicted displacement and collision mortality on the SPA population.
Collision Risk - Operation and Maintenance
  1. As for displacement, breeding season collision estimates attributed to the East Caithness Cliffs SPA kittiwake population were extracted from the existing assessments for offshore wind farms that are in planning, consented, under construction or in operation (Offshore EIA Report, volume 3, appendix 11.6, annex E). Kittiwake collision estimates for the non-breeding periods were derived from the information collated in the East Anglia TWO and East Anglia ONE North submissions (MacArthur Green and Royal HaskoningDHV 2021), with the collision numbers for some projects updated using more recent design information where required (Offshore EIA Report, volume 3, appendix 11.6, annex E). Options based on consented and ‘as-built’ designs were also considered but for the current SPA population this had minimal effects, with the respective totals differing by approximately one adult bird. Therefore, only the estimates for the consented designs are considered in this case. The non-breeding season collision estimates were apportioned to the East Caithness Cliffs SPA population according to the BDMPS approach (Furness 2015).
  2. In contrast to the displacement estimates derived for the other projects, existing collision estimates for these projects were not adjusted to align with the Scoping Approach of using the maximum (rather than the mean) monthly estimate of the density of birds in flight (with all of the other projects likely to have followed the ‘standard’ approach of using the mean density). Such an adjustment would require the re-calculation of the CRMs for each project, which would not be feasible in many cases because of the difficulty in accessing the appropriate baseline data.
  3. As for displacement, the potential mortality estimates derived for the other projects were combined with those for the Proposed Development to give estimates the Proposed Development in-combination with the other UK North Sea wind farms according to both the Scoping Approach and Developer Approach ( Table 5.170   Open ▸ ).

 

Table 5.170:
Predicted collision effects on the East Caithness Cliffs SPA kittiwake population due to the Proposed Development in-combination with other projects in the UK North Sea waters. Estimates are presented for both the Scoping Approach and Developer Approach.

Table 5.170: Predicted collision effects on the East Caithness Cliffs SPA kittiwake population due to the Proposed Development in-combination with other projects in the UK North Sea waters. Estimates are presented for both the Scoping Approach and Developer Approach.

  1. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult kittiwakes from the East Caithness Cliffs SPA population predicted due to collisions represents 0.46% of the current adult breeding population at this colony (i.e. 48,920 individuals – Table 3.3 of the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and 0.48% of this population as determined by the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.146 – see Table 2.13 in the Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult collision mortality equate to an increase of 3.18% for the Developer Approach and of 3.28% for the Scoping Approach.
  2. The potential levels of impact on the East Caithness Cliffs SPA kittiwake population resulting from the mortality predicted from collisions 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 combined effects of predicted displacement and collision mortality on the SPA population.
In-Combination: Population-Level Impacts
  1. As for the Proposed Development alone, PVA was undertaken on the mortality to the adult and immature age classes predicted due to the combined displacement and collision effects associated with the Proposed Development in-combination with the other UK North Sea wind farms. This was on the basis of the potential mortality as determined by both the Scoping and Developer Approaches (see Table 5.169   Open ▸ and Table 5.170   Open ▸ above).
  2. 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 5.171:
Projected 35-year population sizes and associated PVA metrics for the East Caithness Cliffs SPA kittiwake population under different impact scenarios for the Proposed Development in-combination with the other UK North Sea wind farms.

Table 5.171: Projected 35-year population sizes and associated PVA metrics for the East Caithness Cliffs SPA kittiwake 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 other UK North Sea wind farms suggest greater population-level impacts than as predicted for the Proposed Development alone (compare Table 5.163   Open ▸ with Table 5.171   Open ▸ ). The CPS value for the Developer Approach indicates that the SPA population size would be reduced by 16.2% relative to the predicted population size under baseline conditions after 35 years, whilst the equivalent reduction for the Scoping Approach is 16.6 – 22.3% ( Table 5.171   Open ▸ ). Reductions in the annual population growth rate (relative to that predicted under baseline conditions) are estimated to be 0.5% for the Developer Approach and 0.5 – 0.7% for the Scoping Approach. The values for the centile metric are estimated as 36.4 after 35 years for the Developer Approach and as 31.6 – 36.0 for the Scoping Approach, suggesting moderate levels of overlap in the distribution of the predicted impacted and unimpacted population sizes and, hence, a reasonable likelihood of the impacted population being smaller than the unimpacted population after 35 years.
  2. The context within which the PVA metrics from these in-combination scenarios should be considered is outlined above in the Project Alone: Population-Level Impacts section for this SPA population.
In-Combination: Conclusion
  1. For both the Scoping and Developer Approaches, the predicted levels of impact associated with the in-combination scenario represent a marked increase compared to those associated with the Proposed Development alone. These levels of impact suggest the potential for the in-combination effects to lead to a marked reduction in the size of the East Caithness Cliffs SPA population after 35 years relative to that which would occur in the absence of these effects. The predicted levels of impact are such that for the Developer Approach (which predicts lower levels of impact than the Scoping Approach), this potential reduction in population size is c.16% for the Proposed Development in-combination with the other UK North Sea wind farms.
  2. The centile values indicate a moderate likelihood of the impacted population being similar in size to the un-impacted population after 35 years whilst the context that has been outlined for both St. Abb’s Head to Fast Castle SPA and Forth Islands SPA in relation to (i) the high levels of precaution incorporated in the assessment and (ii) the likelihood that the effects from wind farm developments will be of minor importance relative to other management and environmental factors in determining the future status of the SPA kittiwake population, remains highly relevant. However, despite this, it is considered that the scale of the potential reduction in the size of the SPA population associated with the in-combination effects means that the possibility of adverse effects on the SPA population cannot be excluded.
  3. Consequently, it is concluded that there is the potential for an adverse effect on the East Caithness Cliffs SPA kittiwake population as a result of the predicted effects from the Proposed Development in-combination with the other UK North Sea wind farms. This conclusion applies to the assessments undertaken according to both the Developer Approach and the Scoping Approach.

Assessment for the Razorbill Population

  1. The East Caithness Cliffs SPA razorbill population is currently estimated to number 40,117 individuals based upon the most recently available count data from 2015 (Offshore EIA Report, volume 3, appendix 11.5), which represents a 69.5% increase since the last count in 1999 (when the population was estimated at 17,727 individuals).

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 East Caithness Cliffs SPA, so that potential impacts on its razorbill 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).
  2. From published information on razorbill foraging ranges generally (Woodward et al., 2019) and inference from tracking data (Wakefield et al., 2017), it is apparent that during the breeding period, a relatively small proportion of razorbills from the East Caithness Cliffs SPA may occur within the area of the Proposed Development and two kilometre buffer. This is reflected in the findings of the apportioning exercise, which estimates that approximately 2.3% of the razorbills 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 NatureScot advice received following Roadmap Meeting 6 (K. Taylor, email 20/05/2022), 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 East Caithness Cliffs 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 East Caithness Cliffs SPA razorbill population during breeding and non-breeding periods.
Project Alone: Construction and Decommissioning
Disturbance
  1. Direct disturbance to razorbills during the assumed eight-year construction phase may arise within the Proposed Development as a result of increased vessel movements, as well as from other activities directly associated with the installation of the turbine foundations and other infrastructure (see Table 4.1).
  2. 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.
  3. Tracking data (and associated modelling of foraging distributions) for razorbill suggest that the Proposed Development array area and offshore export cable corridor are beyond waters that are heavily used by birds from the East Caithness Cliffs SPA during the breeding season (Wakefield et al., 2017).
  4. Indeed, the Proposed Development is situated at the very edge of the breeding season foraging area of razorbills from the East Caithness Cliffs SPA (i.e. 88.7±75.9 km - Woodward et al., 2019). For those razorbills foraging beyond their core range during the breeding period, the total area to be affected by such disturbance over the assumed eight years of the construction phase represents a small proportion of the total area of marine habitat available to razorbills from the East Caithness Cliffs SPA. Thus, the Proposed Development array area encompasses 1,010 km2, whilst the Proposed Development offshore 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 main seaward side of the colony.
  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, it is important to consider that the construction activities will not occur simultaneously across the entirety of the Proposed Development array area and offshore 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.
  7. Given the moderate sensitivity of razorbill to disturbance effects at sea (Garthe and Hüppop 2004, Furness et al., 2013), and the relatively small areas that will be subject to activities with the potential to result in intermittent, temporary disturbance (relative to the foraging range of razorbills breeding at East Caithness Cliffs SPA), it is considered that there is no potential for construction or decommissioning related disturbance to lead to an adverse effect on the East Caithness Cliffs 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 East Caithness Cliffs 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 and offshore 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. Therefore, based upon the above, it is considered that there is relatively little potential for the East Caithness Cliffs SPA razorbill population to be affected by displacement during the construction or decommissioning phases. Consequently, it is considered that there is no potential for construction or decommissioning related displacement to lead to an adverse effect on the East Caithness Cliffs 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 East Caithness Cliffs 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 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 razorbill population. The evidence base and context for assessing the potential for such effects to have impacts on the East Caithness Cliffs SPA razorbill population is as for the St Abb’s Head to Fast Castle SPA razorbill population (which is detailed above in the equivalent section for this SPA population).
  3. Given this, it is considered that there is relatively little potential for the East Caithness Cliffs 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 East Caithness Cliffs SPA razorbill population.
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 East Caithness Cliffs SPA for the reasons given in the section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population.
  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 Project Alone: Operation and Maintenance – Disturbance for the St. Abb’s Head to Fast Castle SPA razorbill 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 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 operational and maintenance phase will not occur simultaneously across the entirety of the Proposed Development array area and offshore 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 East Caithness Cliffs SPA razorbill population.
Displacement / Barrier Effects
  1. For the reasons given in Table 2.1   Open ▸ and section 5.4, displacement effects on the East Caithness Cliffs 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 in the Offshore EIA Report, volume 3, appendix 11.4 and in the section on Project Alone: Operation and Maintenance – Displacement/Barrier Effects for the St Abb’s Head to Fast Castle SPA razorbill population.
  2. On the basis of the advice provided in the Scoping Opinion ( Table 2.1   Open ▸ ), 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:
  • 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. However, the approach to estimating razorbill displacement effects advocated by the Scoping Opinion was considered overly precautionary in relation to both the displacement and mortality rates that were proposed, as detailed in the Offshore EIA Report, volume 3, appendix 11.4, annex G. In particular, 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. Thus, based on a consideration of the available evidence for razorbill 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 (Offshore EIA Report, volume 3, appendix 11.4, annex G). 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 razorbill 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 East Caithness Cliffs SPA razorbill 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). 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 East Caithness Cliffs SPA razorbill PVAs in this assessment (as presented in the Offshore EIA Report, volume 3, appendix 11.6, annex F). 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 5.172:
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 East Caithness Cliffs SPA population in each period. The proportion of adults assumed to be sabbaticals during the breeding season is also presented.

Table 5.172: 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 East Caithness Cliffs SPA population in each period. The proportion of adults assumed to be sabbaticals during the breeding season is also presented.

 

Table 5.173:
Estimated potential annual mortality of East Caithness Cliffs 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 5.173: Estimated potential annual mortality of East Caithness Cliffs 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. 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 5.3 adult and 3.6 immature birds based on the lower mortality rates of Scoping Approach A, and 14.8 adult and 9.9 immature birds based upon the higher mortality rates of Scoping Approach B ( Table 5.173   Open ▸ ). The displacement effects predicted by the Scoping Approach are largely attributable to the passage periods (with the potential passage period mortality accounting for approximately 85% of the overall annual mortality – Table 5.173   Open ▸ ).
  2. The annual mortality from displacement as determined using the Developer Approach is predicted to be 3.7 adult and 2.6 immature birds, again largely attributable to the passage periods (Offshore EIA Report, volume 3, appendix 11.4, annex G).
  3. The additional annual mortality of adult razorbill from the East Caithness Cliffs 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. 40,117 individuals – Table 3.3 of the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and between approximately 0.01 – 0.04% 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 0.09 – see Table 2.13 in the Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult mortality equate to an increase of 0.10% for the Developer Approach and of 0.15 – 0.41% for the lower and upper estimates from the Scoping Approach.
  4. The potential levels of impact on the East Caithness 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.