Project alone: construction and decommissioning
Disturbance
  1. Direct disturbance to kittiwakes during the construction phase may arise within the Proposed Development array area (and its immediate vicinity) as a result of increased vessel movements and helicopter activity, as well as from other activities directly associated with the installation of the wind turbine foundations and other infrastructure, whilst there will also be increased vessel activity along the Proposed Development export cable corridor due to the cable laying activities. The levels of such activities that could arise are outlined in Table 4.1, with these activities occurring during construction campaigns within a construction period of at most eight years duration.
  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), kittiwakes are considered to have a relatively low sensitivity to such sources of direct disturbance. Thus, reviews of the sensitivity of different seabird species to disturbance from vessels and helicopter traffic assign kittiwake as ‘2’ on a five-scale ranking system, where 1 indicates hardly any or limited escape/avoidance behaviour and very short flight distance when approached and 5 indicates strong escape/avoidance behaviour and a large response distance (Garthe and Hüppop 2004, Furness et al. 2013).
  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 kittiwakes from the Buchan Ness to Collieston Coast SPA. Thus, the Proposed Development array area encompasses 1,010 km2, whilst the Proposed Development export cable corridor encompasses 168 km2. Together these areas represent less than 1% of the total breeding season foraging area that is potentially available to the SPA kittiwake population, as defined by the generic measure of the species’ mean maximum breeding season foraging range plus 1 SD (i.e.156.1±144.5 km - Woodward et al. 2019) and assuming that this range is represented by a semicircle to the seaward side of the colony. Similarly, the Proposed Development array and export cable corridor represent approximately 3% of the breeding season foraging area if considering the mean maximum foraging range only.
  5. Tracking data (and associated modelling of foraging distributions) for kittiwake suggest that the Proposed Development array area and Proposed Development export cable corridor are beyond waters that are heavily used by birds from the Buchan Ness to Collieston Coast SPA during the breeding season (Cleasby et al. 2018).
  6. During the non-breeding periods, kittiwake distribution is not constrained by the location of the breeding colonies and birds from the SPA population are likely to occur across large expanses of oceanic and maritime waters (Frederiksen et al. 2012, Furness 2015). Thus, the potential for effects of construction-related disturbance is generally lower than during the breeding season (but noting that in the case of the Buchan Ness to Collieston Coast SPA, the distance of the SPA from the Proposed Development means that the likelihood of usage of the Proposed Development by the SPA birds during the breeding season is also low and, hence, any such seasonal effect will be less marked).
  7. In addition, it is important to consider that the construction activities will not occur simultaneously across the entirety of the Proposed Development array area or the Proposed Development export cable corridor but, rather, will be carried out in different areas at different times. Thus, the activities will be concentrated within discrete (often small) parts of these wider areas, and within such areas they will not extend over the full duration of the construction phase, so further reducing the potential to which birds may be subject to disturbance effects. For example, cable laying for the Proposed Development export cable will occur over a total of two years, whilst within the Proposed Development array area it is likely that construction activities would be confined largely to discrete areas at any one time.
  8. 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.
  9. Given the low sensitivity of kittiwake to disturbance effects, the large distance of the Proposed Development from the SPA (relative to the estimated kittiwake breeding season foraging range), the relatively small areas that will be subject to activities with the potential to result in disturbance at any given time during the construction period and the fact that these potential effects will be temporary, it is considered that there is no potential for construction or decommissioning related disturbance to lead to an adverse effect on the Buchan Ness to Collieston Coast SPA kittiwake population. This conclusion is consistent with the outcome of the EIA which ‘screened’ out kittiwake as a species for which detailed consideration of the effects of construction disturbance was required (volume 2, chapter 11 of the Offshore EIA Report).
Displacement
  1. As detailed above, kittiwake is considered to have a low sensitivity to disturbance, whilst potential effects of disturbance during the construction and decommissioning phases will only extend across a small part of the wider foraging areas used by the Buchan Ness to Collieston Coast SPA kittiwake population and be limited to, at most, an eight year period during construction (and a likely similar or shorter period during decommissioning). Furthermore, as detailed above, potential effects of disturbance will not occur simultaneously across the entirety of the Proposed Development array area or Proposed Development export cable corridor but, rather, will be carried out in different areas at different times. Thus, at any given time the potential for disturbance effects that could lead to displacement of kittiwakes from this SPA will be limited to relatively small areas, with the potential effects also being of a temporary nature.
  2. Therefore, based upon the above, it is considered that there is relatively little potential for the Buchan Ness to Collieston Coast SPA kittiwake population to be affected by displacement during the construction or decommissioning phases, with any such effects only extending across relatively small areas and tending to be temporary in nature. Consequently, it is considered that there is no potential for construction or decommissioning related displacement to lead to an adverse effect on the Buchan Ness to Collieston Coast SPA kittiwake population. This conclusion is consistent with the outcome of the EIA which ‘screened’ out kittiwake as a species for which detailed consideration of the effects of construction-related displacement was required (volume 2, chapter 11 of the Offshore EIA Report).
Changes to prey availability
  1. Key prey species for kittiwakes include sandeel and sprat (del Hoyo et al., 1996). Indirect effects on kittiwakes may arise as a result of changes in the availability, distribution, or abundance of these species during the construction and decommissioning phases of the Proposed Development. Reduction or disruption to prey availability may cause displacement from foraging grounds or reduced energy intake, affecting survival rates or productivity in the Buchan Ness to Collieston Coast SPA kittiwake 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 kittiwake population. The same evidence basis and context applies to the Buchan Ness to Collieston Coast SPA kittiwake population as to the St Abb’s Head to Fast Castle SPA population in relation to the potential for such effects to lead to impacts on the population. Additionally, the large distance of the Proposed Development from the Buchan Ness to Collieston Coast SPA (relative to the breeding season foraging range) is relevant because it reduces the likelihood that kittiwakes from this SPA will use the Proposed Development during the breeding season (Offshore EIA Report, volume 3, appendix 11.5).
  3. Given this, it is considered that there is relatively little potential for the Buchan Ness to Collieston Coast SPA kittiwake population to be affected by changes to prey availability during the construction and decommissioning phases, with any such effects being largely intermittent across a relatively small spatial extent, with most effects temporary in nature. Consequently, it is considered that there is no potential for construction or decommissioning related changes in prey availability to lead to an adverse effect on the Buchan Ness to Collieston Coast SPA kittiwake 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 kittiwakes from Buchan Ness to Collieston Coast SPA. As described in the section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population, kittiwakes are considered to have a relatively low sensitivity to such sources of direct disturbance at sea (Garthe and Hüppop 2004, Furness et al., 2013).
  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 St Abb’s Head to Fast Castle SPA kittiwake population and in volume 2, chapter 13 of the Offshore EIA Report, 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 Buchan Ness to Collieston Coast SPA kittiwake population.
Displacement/barrier effects
  1. As outlined above, the SNCB matrix approach provides the basis for estimating displacement effects on seabird species in this assessment, with this approach assumed to also incorporate the impact of barrier effects within the estimates that are derived (SNCBs 2022, Offshore EIA Report, volume 3, appendix 11.4). Thus, throughout this section, mortality from displacement is assumed to refer to that which results from both displacement and barrier effects. The approach used to derive predicted levels of mortality is as described in the section on Project Alone: Operation and Maintenance – Displacement/Barrier Effects for the St Abb’s Head to Fast Castle SPA kittiwake population above (and in the Offshore EIA Report, volume 3, appendix 11.4).
  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 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 volume 3, appendix 11.4, annex G of the Offshore EIA Report. In particular, it represented a marked change from the assumptions applied in assessments for other recent Scottish offshore wind farms (Marine Scotland 2017a,b,c) with no clear evidence apparently being available to justify such a change. Thus, based on a consideration of the available evidence for kittiwake displacement, the extent of the species’ ranging behaviour (particularly in the non-breeding periods), previous precedent and a need to incorporate precaution within the assessment, an alternative Developer Approach to estimating displacement effects was determined (volume 3, appendix 11.4, annex G of the Offshore EIA Report). The rates adopted by the Developer Approach are:
  • Breeding period: 30% displacement with a mortality rate of 2%.
  • Non-breeding periods: No measurable effects of displacement on mortality.
    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 Buchan Ness to Collieston Coast SPA kittiwake population during the breeding and non-breeding periods according to the MS Apportioning Tool (Butler et al. 2020) and the BDMPS approach (Furness 2015), respectively (Offshore EIA Report, volume 3, appendix 11.5, Table 5.132). The resulting mortality estimates for the breeding period were apportioned to age classes on the basis of the plumage characteristics of kittiwakes recorded during the breeding period in the baseline surveys (Offshore EIA Report, volume 3, appendix 11.1), whilst for the non-breeding periods age classes were apportioned according to the stable age distributions of the population model used in Furness (2015). Based on advice provided by NatureScot and Marine Scotland Science following Roadmap Meeting 4 (G. Holland, email 26/01/2022), it was also assumed that 10% of the breeding adults in the SPA population miss breeding in any given year (i.e. sabbatical birds) so that the number of estimated adult deaths during the breeding season was adjusted accordingly.

 

Table 5.132:
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 Buchan Ness to Collieston Coast SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals during the Breeding Season is also Presented

Table 5.132: 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 Buchan Ness to Collieston Coast SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals during the Breeding Season is also Presented

 

  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 two adult and one immature birds based on the lower mortality rates for the Scoping Approach (i.e. Scoping Approach A) and as seven adult and three immature birds based upon the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B) (Table 5.133). The displacement effects predicted by the Scoping Approach are attributable mainly to the non-breeding season (which accounts for almost 80% of the overall potential annual mortality – Table 5.133), reflecting the fact that this SPA is distant from the Proposed Development with a low likelihood of use by the SPA kittiwake population during the breeding season.
  2. The annual mortality from displacement as determined using the Developer Approach is predicted to be approximately one adult bird, which (in contrast to the estimates from the Scoping Approach) is entirely attributable to breeding season effects (on the basis that displacement effects on kittiwake during the non-breeding periods are not considered to result in detectable impacts on the population – volume3, appendix 11.4, annex G of the Offshore EIA Report).

 

Table 5.133:
Estimated Potential Annual Mortality of Buchan Ness to Collieston Coast 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 5.133: Estimated Potential Annual Mortality of Buchan Ness to Collieston Coast 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. The additional annual mortality of adult kittiwakes from the Buchan Ness to Collieston Coast SPA population predicted due to displacement from the Proposed Development array represents less than 0.01% of the current adult breeding population at this colony (i.e. 22,590 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and between approximately 0.01 – 0.03% of this population as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.145 – see Table 2.13 in volume 3, appendix 11.6 of the Offshore EIA Report), the estimates of adult mortality equate to an increase of less than 0.1% for the Developer Approach and of approximately 0.1 – 0.2% for the lower and upper estimates from the Scoping Approach.
  2. The potential levels of impact on the Buchan Ness to Collieston Coast SPA kittiwake population resulting from the mortality predicted from displacement and barrier effects associated with the Proposed Development array during the operation and maintenance phase are considered in more detail below in the Project Alone: Population-Level Impacts section. This presents the outputs from PVAs of the combined effects of predicted displacement and collision mortality on the SPA population.
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 (volume 3, appendix 6.2 of the Offshore EIA Report), 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. As detailed for the St Abb’s Head to Fast Castle SPA kittiwake population, 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)8 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 array area. Further details on this 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 volume 3, appendix 11.3 of the Offshore EIA Report) but, as a result of this overly precautionary approach (which does not follow previous precedent), the CRMs for Buchan Ness to Collieston Coast SPA kittiwakes were undertaken following:
  • The Scoping Approach of using the maximum monthly densities, and
  • The Developer Approach of using the mean monthly densities.
    1. As for the St Abb’s Head to Fast Castle SPA kittiwake population, collision estimates were also calculated:
  • Using option 2 of the deterministic version of the CRM but with site-specific flight height data from boat-based surveys of the Proposed Development array area10 (as opposed to the generic flight height data of Johnston et al. 2014a,b).
  • Using options 2 and 3 of the stochastic version of the CRM (McGregor et al. 2018) with avoidance rates as derived from the bird collision-avoidance study undertaken at the Thanet offshore wind farm (Bowgen and Cook 2018), noting that option 3 of the CRM uses the modelled flight height distributions from Johnston et al. (2014a,b).
    1. These additional collision estimates are not used as the basis of the assessments on the SPA kittiwake populations but, instead, are used in a comparative way to illustrate the extent to which some estimates may vary according to certain of the key assumptions on which they are based. Details of these additional CRMs are provided in annex B and annex C of Offshore EIA Report, volume 3, appendix 11.3.
    2. As for the 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 Buchan Ness to Collieston Coast 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, Table 5.132). The age class proportions and assumptions on sabbatical rates are also as detailed above in relation to displacement effects (Table 5.132).
    3. 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 Buchan Ness to Collieston Coast SPA is predicted to be approximately 14 adults and four immatures as determined by the Scoping Approach, and approximately 10 adults and three immatures as determined by the Developer Approach (Table 5.134). The majority of this mortality (i.e. 64%) is predicted to occur during the non-breeding season (for the same reasons as outlined above for the displacement effects on this SPA population, as determined by the Scoping Approach).

 

Table 5.134:
Predicted Collision Effects from the Proposed Development on the Buchan Ness to Collieston Coast SPA Kittiwake Population, as Determined by the Scoping Approach and Developer Approach. Estimates are for the Maximum Design Scenarioand are Based on Option 2 of the Deterministic CRM Using a 98.9% Avoidance Rate (see text)

Table 5.134: Predicted Collision Effects from the Proposed Development on the Buchan Ness to Collieston Coast SPA Kittiwake Population, as Determined by the Scoping Approach and Developer Approach. Estimates are for the Maximum Design Scenarioand are Based on Option 2 of the Deterministic CRM Using a 98.9% Avoidance Rate (see text)

 

  1. The additional annual mortality of adult kittiwakes from the Buchan Ness to Collieston Coast SPA population predicted due to collisions with wind turbines in the Proposed Development array represents approximately 0.04% of the number of adults currently estimated to breed at this colony (i.e. 22,590 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach and approximately 0.06% 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 0.145 – see Table 2.13 in volume 3, appendix 11.6 of the Offshore EIA Report), the predicted adult collision mortality equates to increases of 0.3% and 0.4% for the Developer and Scoping Approaches, respectively.
  2. As outlined in the Project Alone: Operation and Maintenance - Collision Risk section for the St Abb’s Head to Fast Castle SPA kittiwake population, using the collision estimates derived from the site-specific flight height data or from the stochastic CRM with avoidance rates as calculated for the bird collision-avoidance study (Bowgen and Cook 2018) would result in predicted collision mortalities on the Buchan Ness to Collieston Coast SPA kittiwake population that are at least 50% lower than those presented in Table 5.134 above (and on which the assessment is based).
  3. More detailed consideration of the potential population-level impacts associated with the predicted collision mortalities in Table 5.134 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 Buchan Ness to Collieston Coast SPA during the operation and maintenance phase have been assessed in volume 2, chapter 9 of the Offshore EIA Report using the appropriate maximum design scenarios for these receptors. Reduction or disruption to prey availability through temporary and long-term subtidal habitat loss/disturbance, increased SSC and deposition, EMF from subsea electrical cabling, and colonisation of subsea structures, could affect kittiwake survival and productivity in the Buchan Ness to Collieston Coast 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 Buchan Ness to Collieston Coast 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 Buchan Ness to Collieston Coast 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 Buchan Ness to Collieston Coast 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 Buchan Ness to Collieston Coast SPA kittiwake population are displacement (inclusive of 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 Tables 5.133 and 5.134 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 volume 3, appendix 11.6 of the Offshore EIA Report. The starting population size was the 2019 count for the SPA, with the projected population trends considered over a 35 year timescale (Offshore EIA Report volume 3, appendix 11.5). The approach and methods to undertaking the PVA are as described in the section on Project Alone: Population-Level Impacts for St Abb’s Head to Fast Castle SPA kittiwake population above (with further details provided in the 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:
  • 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 5.135:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Buchan Ness to Collieston Coast SPA Kittiwake Population Under Different Impact Scenarios for the Proposed Development Alone

Table 5.135: Projected 35 Year Population Sizes and Associated PVA Metrics for the Buchan Ness to Collieston Coast SPA Kittiwake Population Under Different Impact Scenarios for the Proposed Development Alone

 

  1. The PVA predicted a continuing decline in the size of the Buchan Ness to Collieston Coast SPA kittiwake population over the 35 year projection period, irrespective of the effects from the Proposed Development. Thus, the population is predicted to decline by 81% from the current estimate of 22,590 adult birds under all scenarios, including baseline conditions which assume no wind farm effects (Table 5.135). Although the predicted declines in population size are inevitably smallest 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 the upper range of the Scoping Approach (i.e. Scoping Approach B), the CPS value indicates a reduction of 3% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects (Table 5.135). The associated reduction in annual population growth rate (relative to that predicted under baseline conditions) is 0.1%, whilst the centile value of 47.3 indicates a considerable overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a high likelihood of the impacted population being of a similar size to the un-impacted population after 35 years. As would be expected, the metrics for the lower range of the Scoping Approach and the Developer Approach suggest even smaller levels of impact (Table 5.135).
  3. The PVA outputs described above, and detailed in Table 5.135, need to be considered within the context of the fact that the SPA population is predicted to decline irrespective of the wind farm effects and that such a trend is broadly consistent with the documented long-term trend for this population (see above). As described in the Project Alone: Population-Level Impacts section for the St Abb’s Head to Fast Castle SPA kittiwake population, the available evidence suggests that the long-term decline of kittiwake populations in the North Sea (including the Buchan Ness to Collieston Coast SPA) is associated with fisheries management and climate change (Frederiksen et al. 2004). Therefore, without appropriate management to mitigate these effects, it is likely that the Buchan Ness to Collieston Coast SPA population will continue to decline and that the predicted effects from the Proposed Development may be of limited importance relative to these broader-scale effects. Furthermore, it is also relevant to consider the high levels of precaution incorporated within the assessment, particularly as determined by the Scoping Approach (with this also detailed in the Project Alone: Population-Level Impacts section for the St Abb’s Head to Fast Castle SPA kittiwake population).
Project alone: conclusion
  1. For both the Developer and Scoping Approaches, the potential effects from the Proposed Development alone on the Buchan Ness to Collieston Coast SPA kittiwake population are predicted to be small, with the resultant population-level impacts also predicted to be small. In addition, the PVA metrics indicate a 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 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. As detailed above, any effects from the Proposed Development alone on the Buchan Ness to Collieston Coast 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 Buchan Ness to Collieston Coast 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. Following advice from NatureScot provided through the Ornithology Roadmap process (at meeting 3, 8th December 2021), the following sections consider these potential effects for two in-combination scenarios, i.e. (i) the Proposed Development in-combination with the other Forth and Tay offshore wind farms and (ii) the Proposed Development in-combination with the offshore wind farms in the UK North Sea (noting that scenario (ii) includes those plans and projects which comprise scenario (i)).
Displacement/barrier effects – operation and maintenance
  1. As described in Offshore EIA Report annex A of volume 3, appendix 11.6, estimates of breeding season displacement mortality which had been attributed to the Buchan Ness to Collieston Coast 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, 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. Few estimates of displacement mortality are available from other projects for kittiwake (for any SPA population) during the non-breeding periods because such effects have not been considered important in most 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 annex E in volume 3, appendix 11.6), with the in-combination estimates derived according to the Scoping and Developer approaches as detailed above 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 for both the Forth and Tay wind farm scenario and the UK North Sea wind farm scenario, according to both the Scoping Approach and Developer Approach (Table 5.136).

 

Table 5.136:
Estimated Annual Mortality of Buchan Ness to Collieston Coast 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 Forth and Tay Wind Farms and other UK North Sea Wind Farms

Table 5.136: Estimated Annual Mortality of Buchan Ness to Collieston Coast 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 Forth and Tay Wind Farms and other UK North Sea Wind Farms

 

  1. The incorporation of the potential mortality resulting from the predicted displacement effects associated with other plans and projects increases the levels predicted for the Proposed Development alone for the Scoping Approach but not for the Developer Approach (because the predicted effects from the other plans and projects are limited to the non-breeding periods and the Developer Approach assumes that displacement during the non-breeding periods does not result in detectable impacts on the population – volume 3, appendix 11.4, annex G of the Offshore EIA Report). For the Scoping Approach, these increases are by factors of approximately 1.5 and four for the Proposed Development in-combination with the other Forth and Tay wind farms and the Proposed Development in-combination with the other UK North Sea wind farms, respectively (Tables 5.133 and 5.136).
  2. For the Scoping Approach, the vast majority (i.e. 86 – 95%) of the of the predicted mortality from displacement is attributed to effects during the non-breeding periods (Table 5.136).
  3. For the Proposed Development in-combination with the other Forth and Tay wind farms, the additional annual mortality of adult kittiwakes from the Buchan Ness to Collieston Coast SPA population predicted due to displacement represents less than 0.01% of the current adult breeding population at this colony (i.e. 22,590 individuals – Table 3.3 in the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and between approximately 0.02 – 0.05% of this population as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.145 – see Table 2.13 in the Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult displacement mortality equate to an increase of less than 0.1% for the Developer Approach and of 0.1 – 0.3% for the lower and upper estimates from the Scoping Approach.
  4. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult kittiwakes from the Buchan Ness to Collieston Coast SPA population predicted due to displacement represents between approximately 0.04 – 0.12% of the current adult breeding population at this colony 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, the estimates of adult displacement mortality equate to an increase of 0.3 – 0.8% for the lower and upper estimates from the Scoping Approach. The equivalent figures for the predicted additional mortality as determined by the Developer Approach are as for the Proposed Development in-combination with the other Forth and Tay wind farms (and also as for the Proposed Development alone).
  5. The potential levels of impact on the Buchan Ness to Collieston Coast 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 Forth and Tay or in-combination with other wind farms in the UK North Sea during the operation and maintenance phase are considered in more detail below in the Effects In-Combination: Population-Level Impacts section. This presents the outputs from PVAs of the 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 Buchan Ness to Collieston Coast 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 annex E of volume 3, appendix 11.6). 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, annex E of volume 3, appendix 11.6). The non-breeding season collision estimates were apportioned to the Buchan Ness to Collieston Coast SPA population according to the BDMPS approach (Furness 2015).
  2. Collision estimates based on consented and ‘as-built’11 designs were also considered (Offshore EIA Report, annex E of volume 3, appendix 11.6). For the current SPA population this did not affect the collision estimates for the other Forth and Tay wind farms but had a small effect on those for the other UK North Sea wind farms (with the respective totals for adults and immatures differing by approximately five and three collisions, respectively).
  3. 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.
  4. As for displacement, the potential mortality estimates derived for the other projects were combined with those for the Proposed Development to give estimates 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 according to both the Scoping Approach and Developer Approach (noting that for the Scoping Approach it is only the estimates for the Proposed Development that are calculated according to this approach) (Table 5.137).

 

Table 5.137:
Predicted Collision Effects on the Buchan Ness to Collieston Coast SPA Kittiwake Population due to the Proposed Development In-Combination with Other Projects in the Forth and Tay and in UK North Sea Waters. Estimates are presented for both the Scoping Approach and Developer Approach

Table 5.137: Predicted Collision Effects on the Buchan Ness to Collieston Coast SPA Kittiwake Population due to the Proposed Development In-Combination with Other Projects in the Forth and Tay and in UK North Sea Waters. Estimates are presented for both the Scoping Approach and Developer Approach

 

  1. The potential mortality resulting from the predicted collision effects associated with other plans and projects increases that predicted for the Proposed Development alone by 21 – 27% for the other Forth and Tay wind farms in-combination scenario and by factors of approximately five to seven for the other UK North Sea wind farms in-combination scenario (with the greater increases associated with the Developer Approach in each case - Tables 5.134 and 5.137). As for the Proposed Development alone, the majority of the collision mortality predicted on the SPA population (i.e. approximately 70%) is again attributable to effect during the non-breeding passage periods (Table 5.137).
  2. For the Proposed Development in-combination with the other Forth and Tay wind farms, the additional annual mortality of adult kittiwakes from the Buchan Ness to Collieston Coast SPA population predicted due to collisions represents 0.06% of the current adult breeding population at this colony (i.e. 22,590 individuals – Table 3.3 in the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and 0.08% 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 0.145 – 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 0.4% for the Developer Approach and of 0.5% for the Scoping Approach.
  3. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult kittiwakes from the Buchan Ness to Collieston Coast SPA population predicted due to collisions represents 0.30% of the current adult breeding population at this colony (i.e. 22,590 individuals – Table 3.3 in the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and 0.32% 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 0.145 – 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 2.0% for the Developer Approach and of 2.2% for the Scoping Approach.
  4. Using the collision estimates for the ‘as-built’ (as opposed to the consented) designs reduces the total annual collision estimates for the Proposed Development in-combination with the other UK North Sea wind farms to 66.5 adult and 20.6 immature birds for the Scoping Approach and to 62.3 adult and 19.3 immature birds for the Developer Approach. These potential mortalities would give estimates of the additional annual collision mortality as a percentage of the current adult population and as a percentage increase to the baseline annual adult mortality which are slightly lower than those given in the paragraph above for the Developer Approach. Use of the ‘as-built’ designs does not affect the annual collision estimates for the Proposed Development in-combination with the other Forth and Tay wind farms.
  5. The potential levels of impact on the Buchan Ness to Collieston Coast SPA kittiwake population resulting from the mortality predicted from collisions associated with the Proposed Development in-combination with other wind farms in the Forth and Tay or in-combination with other wind farms in the UK North Sea during the operation and maintenance phase are considered in more detail below in the Effects In-Combination: Population-Level Impacts section. This presents the outputs from PVAs of the 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 Forth and Tay wind farms and the Proposed Development in-combination with the other UK North Sea wind farms. This was on the basis of the potential mortality as determined by both the Scoping and Developer Approaches (see Tables 5.136 and 5.137 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 5.138:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Buchan Ness to Collieston Coast SPA Kittiwake Population Under Different Impact Scenarios for the Proposed Development In-Combination with the other Forth and Tay Wind Farms

Table 5.138: Projected 35 Year Population Sizes and Associated PVA Metrics for the Buchan Ness to Collieston Coast SPA Kittiwake Population Under Different Impact Scenarios for the Proposed Development In-Combination with the other Forth and Tay Wind Farms

 

Table 5.139:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Buchan Ness to Collieston Coast SPA Kittiwake Population Under Different Impact Scenarios for the Proposed Development In-Combination with the other UK North Sea Wind Farms.

Table 5.139: Projected 35 Year Population Sizes and Associated PVA Metrics for the Buchan Ness to Collieston Coast 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 either the other Forth and Tay wind farms or the other UK North Sea wind farms suggest greater population-level impacts than as predicted for the Proposed Development alone (compare Table 5.138 and 5.139 with Table 5.135).
  2. However, these impacts remain relatively small for the Proposed Development in-combination with the other Forth and Tay wind farms. Thus, for the upper range of the Scoping Approach (i.e. Scoping Approach B), the CPS value indicates a reduction of 4% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects (Table 5.138). The associated reduction in annual population growth rate (relative to that predicted under baseline conditions) remains at 0.1%, whilst the centile value of 46.6 continues to indicate a considerable overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a high likelihood of the impacted population being of a similar size to the un-impacted population after 35 years. As would be expected, the metrics for the lower range of the Scoping Approach and the Developer Approach suggest even smaller levels of impact (Table 5.138).
  3. The predicted levels of impact are markedly higher for the Proposed Development in-combination with the other UK North Sea wind farms. For the Scoping Approach, the CPS values indicate a reduction of 12 - 14% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects, whilst the associated reduction in annual population growth rate (relative to that predicted under baseline conditions) is 0.3 – 0.4% (Table 5.139). The values of the centile metric (for the Scoping Approach) suggest at least moderate overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a reasonably high likelihood of the impacted population being of a similar size to the un-impacted population after 35 years. As would be expected, the predicted levels of impact are lower for the Developer Approach, with (most notably) the CPS value indicating a 10% reduction in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects.
  4. Undertaking the PVAs on the basis of the collision estimates for the ‘as-built’ (as opposed to the consented) designs for the Proposed Development in-combination with the other UK North Sea wind farms has a small effect only on the values for the resulting PVA metrics (see Tables 3.1 and 3.3 in the Offshore EIA Report, volume 3, appendix 11.6). Therefore, no further consideration is given to the outputs produced using the ‘as-built’ collision estimates.
  5. 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 Proposed Development in-combination with the other Forth and Tay wind farms remain small, whilst the PVA metrics indicate a high chance of the population being of a similar size to that which would occur in the absence of these impacts after 35 years. Given this, it is concluded that the effects associated with this in-combination scenario would not result in an adverse effect on the Buchan Ness to Collieston Coast SPA kittiwake population.
  2. The predicted levels of impact are higher for the Proposed Development in-combination with the other UK North Sea wind farms but for the Developer Approach they are considered to remain at a level which would not be sufficient to result in an adverse effect on the SPA population. This conclusion is reached within the context that has been outlined above 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. By contrast, the higher levels of impact predicted by the Scoping Approach for this in-combination scenario (which suggest a potential reduction in population size of up to 14%) are of a scale which is considered sufficient to potentially lead to an adverse effect on this SPA population, even when taking account of the above context. However, as has been detailed above (and in Offshore EIA Report, volume 3, appendix 11.3), it is considered that the level of effects on kittiwakes assumed by the Scoping Approach are overly precautionary and without any reasonable basis or support from the available evidence. Given this, it is considered that greater weight should be given to the conclusions as determined by the Developer Approach.
  3. Consequently, it is concluded that there is the potential for an adverse effect on the Buchan Ness to Collieston Coast SPA kittiwake population as a result of the predicted effects from the Proposed Development in-combination with the other UK North Sea wind farms, as determined by the Scoping Approach. However, when based upon the Developer Approach, it is concluded that there is no potential for an adverse effect on the SPA population as a result of the predicted effects from the Proposed Development in-combination with the other UK North Sea wind farms.

Assessment for the guillemot population

  1. The Buchan Ness to Collieston Coast SPA guillemot population is currently estimated to number 39,553 individuals, based upon the most recently available count data from 2019 (Offshore EIA Report, volume 3, appendix 11.5). This is more than double the citation level, which is equivalent to 17,280 individuals as derived from the 1986 population estimate (Table 5.131). Count data for the population are sporadic but tend to suggest that numbers have been largely stable since at least the mid-1990s (but noting that the 2007 count is markedly lower than the other three counts which are available between 1995 and 2019) (SMP 2022).
The potential for impacts on the guillemot population
  1. The Proposed Development and two kilometre buffer around the Proposed Development array area7 do not overlap with the Buchan Ness to Collieston Coast SPA, so that potential impacts on its guillemot 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 guillemot foraging ranges generally (Woodward et al. 2019) and tracking from the SPA specifically (Wakefield et al. 2017), it is possible that during the breeding period guillemots from the Buchan Ness to Collieston Coast SPA may 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 1% of the guillemot 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 guillemots 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), during the non-breeding period guillemots are assumed to remain largely within the waters in the region of the breeding colony, as defined by the mean maximum foraging range plus 1 SD (Woodward et al. 2019, Buckingham et al. 2022, Offshore EIA Report, volume 3, appendix 11.5). Therefore, on this basis, the Proposed Development has a similar potential to have effects on the Buchan Ness to Collieston Coast SPA guillemot population during the non-breeding period as during the breeding season, with 3% of the guillemots occurring on the Proposed Development array area during the non-breeding period estimated to derive from this SPA colony (Offshore EIA Report, volume 3, appendix 11.5).
Project alone: construction and decommissioning
Disturbance
  1. Direct disturbance to guillemots during the construction phase may arise within the Proposed Development array area (and its immediate vicinity) as a result of increased vessel movements and helicopter activity, as well as from other activities directly associated with the installation of the wind turbine foundations and other infrastructure, whilst there will also be increased vessel activity along the Proposed Development export cable corridor due to the cable laying activities. The levels of such activities that could arise are outlined in Table 4.1, with these activities occurring during construction campaigns within a construction period of at most eight years duration.
  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), guillemots 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 guillemot 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 guillemots from the Buchan Ness to Collieston Coast SPA. Thus, the Proposed Development array area encompasses 1,010 km2, whilst the Proposed Development export cable corridor encompasses 168 km2. Together these areas represent approximately 3% of the total breeding season foraging area that is potentially available to the SPA guillemot population, as defined by the generic measure of the species’ mean maximum breeding season foraging range plus 1 SD (i.e. 73.2±80.5 km - Woodward et al. 2019) and assuming that this range is represented by a semicircle to the seaward side of the colony. Similarly, the Proposed Development array and export cable corridor represent approximately 14% of the breeding season foraging area if considering the mean maximum foraging range only. Additionally, modelling of guillemot foraging distributions, as derived from tracking data from the chick-rearing period, indicates that the Proposed Development array area and Proposed Development export cable corridor have minimal overlap with waters that are predicted to be used by birds from the Buchan Ness to Collieston Coast SPA and exclude those areas of predicted greatest usage (Cleasby et al. 2018).
  5. During the non-breeding period, guillemot distribution is less constrained by the location of the breeding colonies but (as detailed above), for the purposes of the current assessment, it is assumed that the area occupied by the SPA population is defined by the mean maximum breeding season foraging range plus 1SD. Thus, the potential for effects of construction-related disturbance is assumed to be similar to that 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 guillemot to disturbance effects, the large distance of the Proposed Development from the SPA (relative to the estimated guillemot foraging range), the relatively small areas that will be subject to activities with the potential to result in disturbance at any given time during the construction period and the fact that these potential effects will be temporary, it is considered that there is no potential for construction or decommissioning related disturbance to lead to an adverse effect on the Buchan Ness to Collieston Coast SPA guillemot population.