Collision risk - operation and maintenance
  1. Existing assessments for offshore wind farms that are in planning, consented, under construction or in operation were checked to determine the collision estimates to be attributed to the Farne Islands SPA lesser black-backed gull population during the breeding and non-breeding periods (annex E of Offshore EIA Report, volume 3, appendix 11.6).
  2. None of these assessments identified breeding season effects on the SPA population, noting that the Scoping Opinion for the revised designs of the three Forth and Tay projects (which are in closest proximity to the SPA) did not require this SPA population to be assessed (Marine Scotland 2017a,b,c). Additionally, the Appropriate Assessment for the original consents of the Forth and Tay projects predicted a reduction in adult survival rate of less than 0.1% as a result of the Neart na Gaoithe wind farm and concluded no adverse effect on the SPA population (Marine Scotland 2014).
  3. Cumulative collisions of lesser black-backed gulls for UK North Sea wind farms during the non-breeding periods have been estimated recently as approximately 365 (MacArthur Green and Royal HaskoningDHV 2021). During the non-breeding periods, adult lesser black-backed gulls from the Farne Islands SPA are estimated to comprise less than 1% of the autumn and spring passage populations in the North Sea and Channel BDMPS (each of which number approximately 200,000 birds) and approximately 1.5% of the smaller winter population in this BDMPS (which numbers approximately 39,000 birds) (Furness 2015)[15]. Given this, it is unlikely that more than 1% of the total collisions during the non-breeding periods (i.e. approximately 3.6 individuals) would be adults from the Farne Islands SPA population. Immatures associated with the Farne Islands SPA population are estimated to represent approximately 0.3% of the passage populations and 0.2% of the winter population (Furness 2015), suggesting that fewer than one collision from the total 365 non-breeding season collisions may be attributable to immatures from this SPA population.
  4. Combining the above collision estimates for the non-breeding season with those for the breeding season (Table 5.116) suggests a total of approximately four adult collisions and fewer than a single immature collision for the Proposed Development in-combination with the other UK North Sea wind farms, as determined by the Scoping and Developer Approaches.
  5. The PVA undertaken for the Farne Islands SPA lesser black-backed gull population using incremental mortalities gives a CPS value of 0.884 and a CPGR value of 0.997 for a mortality of four adult birds per year (see Table 3.148 in the Offshore EIA Report, volume 3, appendix 11.6). This suggests a reduction in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects, of almost 12% as determined by the Scoping and Developer Approaches. The centile value associated with this level of mortality is 29.7, suggesting a reasonable likelihood that the impacted population will be similar in size to the un-impacted population after 35 years (see Table 3.148 in the Offshore EIA Report, volume 3, appendix 11.6).
  6. However, the PVA for the incremental mortalities assumes that mortality across age classes occurs in proportion to the asymptotic age distribution (as calculated by the population model). Given that adults are estimated to comprise just 45% of the population, this means that the PVA grossly overestimates the level of immature mortality (relative to that estimated from the in-combination collision effects), meaning that the above metrics represent an overestimation of the population-level impacts.
In-combination: conclusion
  1. On the basis of the above considerations, it is concluded that the population-level impacts resulting from the Proposed Development in-combination with the other UK North Sea wind farms would not produce an adverse effect on the Farne Islands SPA lesser black-backed gull population. This conclusion applies irrespective of whether effects are determined according to the Scoping Approach or the Developer Approach.

Assessment for the guillemot population

  1. The Farne Islands SPA guillemot population is currently estimated to number 85,816 individuals, based upon the most recently available count data from 2019 (Offshore EIA Report, volume 3, appendix 11.5). The SPA population has shown a strongly increasing population trend over the long-term, with numbers increasing (virtually) year on year from an estimated 24,958 individuals in 1986 (SMP 2022). The current population size for this SPA qualifying feature is above the citation level (Table 5.106).
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 Farne Islands 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 of maintaining or restoring the populations of each qualifying feature, because the other conservation objectives either apply to the site itself, and not to areas beyond the boundary, or are encompassed by the assessment of this Conservation Objective (as for maintaining or restoring the structure and function of the habitats of the qualifying features, because habitat structure and function would only be considered significant if it caused an adverse effect on the maintenance or restoration of the population of the qualifying features). In terms of the SACOs, this focus is most closely reflected in the ‘breeding population: abundance’ attribute which has the target of maintaining the abundance of the breeding population of this feature above the citation level, whilst avoiding deterioration from its current levels. Clearly, other attributes (e.g. connectivity with supporting habitats) are also relevant but, as for the conservation objectives above, their significance is linked to whether they prevent achievement of the attribute concerned with maintaining the abundance of the breeding population (see appendix 3A).
  2. From published information on guillemot foraging ranges generally (Woodward et al. 2019) and evidence from tracking data (Wakefield et al. 2017), it is likely that during the breeding period guillemots from the Farne Islands SPA occur within the area of the Proposed Development and of the two km buffer around the Proposed Development array area. This is supported by the findings of the apportioning exercise, which estimates that approximately 9% of the guillemots 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 guillemot 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 Farne Islands SPA guillemot population during the non-breeding period as during the breeding season, with 21% 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 Farne Islands 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 main 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.
  5. Tracking data (and associated modelling of foraging distributions) for guillemot appear to suggest that the Proposed Development array area and Proposed Development export cable corridor are beyond waters that are heavily used by birds from the Farne Islands SPA during the breeding season (Wakefield et al. 2017).
  6. 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.
  7. 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.
  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 moderate sensitivity of guillemot to disturbance effects, the relatively small areas that will be subject to activities with the potential to result in disturbance at any given time during the construction period and the fact that these potential effects will be temporary, it is considered that there is no potential for construction or decommissioning related disturbance to lead to an adverse effect on the Farne Islands SPA guillemot population.
Displacement
  1. As detailed above, guillemot is considered to have a moderate sensitivity to disturbance, whilst potential effects of disturbance during the construction and decommissioning phases will (at most) only extend across a small part of the wider foraging areas used by the Farne Islands SPA guillemot population and be limited to (at most) an eight year period during construction (and a likely similar or shorter period during decommissioning). Furthermore, as detailed above, potential effects of disturbance will not occur simultaneously across the entirety of the Proposed Development array area or Proposed Development export cable corridor but, rather, will be carried out in different areas at different times. Thus, at any given time the potential for disturbance effects that could lead to displacement of guillemots from this SPA will be limited to relatively small areas, with the potential effects also being of a temporary nature.
  2. Based upon the above, it is considered that there is relatively little potential for the Farne Islands SPA guillemot population to be affected by displacement during the construction or decommissioning phases, with any such effects only extending across relatively small areas and tending to be temporary in nature. Consequently, it is considered that there is no potential for construction or decommissioning related displacement to lead to an adverse effect on the Farne Islands SPA guillemot population.
Changes to prey availability
  1. Sandeels are key prey for guillemots, with a range of other species taken including clupeids (sprat and juvenile herring; del Hoyo et al., 1996). Indirect effects on guillemots may arise as a result of changes in the availability, distribution, or abundance of these species during the construction and decommissioning phases of the Proposed Development. Reduction or disruption to prey availability may cause displacement from foraging grounds or reduced energy intake, affecting survival rates or productivity in the Farne Islands SPA guillemot population in the short-term.
  2. During construction and decommissioning there are a number of ways in which effects on key prey species of seabirds may occur, which are outlined in the section on Project Alone: Construction and Decommissioning – Changes to Prey Availability for the St Abb’s Head to Fast Castle SPA kittiwake population. The evidence base and context for assessing the potential for such effects to have impacts on the Farne Islands SPA guillemot population are as for the St Abb’s Head to Fast Castle SPA guillemot population (and are detailed above in the equivalent section for that SPA population).
  3. Given this, it is considered that there is relatively little potential for the Farne Islands SPA guillemot population to be affected by changes to prey availability during the construction and decommissioning phases, with any such effects being largely intermittent across a relatively small spatial extent, with most effects temporary in nature. Consequently, it is considered that there is no potential for construction or decommissioning related changes in prey availability to lead to an adverse effect on the Farne Islands SPA guillemot 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 guillemots from Farne Islands SPA. As described in the section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population, guillemots are considered to have a moderate sensitivity to such sources of direct disturbance at sea (Garthe and Hüppop 2004, Furness et al., 2013).
  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 the Offshore EIA Report, volume 2, chapter 13, baseline levels of vessel traffic in the Offshore Ornithology study area are relatively high. In the context of the baseline levels of vessel traffic across the Offshore Ornithology study area, the increase during the operation and maintenance phase is considered to be relatively small. Vessel movements will be within the Proposed Development array area and export cable corridor and will follow existing shipping routes to/from ports. In addition, Project Codes of Conduct included as a part of the NSVMP (Offshore EIA Report, volume 4, appendix 25) will be issued to all project vessel operators to avoid sudden changes in course or speed which will minimise the potential for disturbance. Within the Proposed Development array area, movements and associated maintenance activities will be restricted to individual wind turbines over a period of days to weeks.
  4. The size and noise outputs from vessels during the operation and maintenance phase will be similar to those used in the construction phase. However, the number of vessel return trips per year and their frequency will be much lower for the operation and maintenance phase compared to the construction phase. In addition, activities during the operation and maintenance phase will not occur simultaneously across the entirety of the Proposed Development array area and export cable corridor but intermittently within discrete (often very small) parts of these wider areas.
  5. Given the discrete areas relative to the species’ foraging range that will be subject intermittently to potential disturbance from vessel use and maintenance activities (Woodward et al., 2019), and the fact that these potential effects will be reduced compared to the construction and decommissioning phases, it is considered that there is no potential for disturbance during operation and maintenance to lead to an adverse effect on the Farne Islands SPA guillemot population.
Displacement/barrier effects
  1. As outlined above, displacement effects on the Farne Islands SPA guillemot population are estimated using the SNCB matrix approach, as applied to the Proposed Development array and two kilometre buffer (SNCBs 2022, Offshore EIA Report, volume 3, appendix 11.4). Thus, throughout this section, mortality from displacement is assumed to refer to that which results from both displacement and barrier effects. The approach used to derive predicted levels of mortality is as described in the section on Project Alone: Operation and Maintenance – Displacement/Barrier Effects for the St Abb’s Head to Fast Castle SPA kittiwake population above (and in the Offshore EIA Report, volume 3, appendix 11.4).
  2. On the basis of the advice provided in the Scoping Opinion (volume 3, appendix 6.2 of the Offshore EIA Report), displacement effects on guillemot are estimated for the breeding and non-breeding periods. The displacement and associated mortality rates advised in the Scoping Opinion (subsequently termed the Scoping Approach) for guillemot are:
  • Breeding period: 60% displacement with lower and upper mortality rates of 3% and 5%.
  • Non-breeding period: 60% displacement with lower and upper mortality rates of 1% and 3%.
    1. As with other species for which displacement effects are assessed (see above), the approach to estimating guillemot displacement effects advocated by the Scoping Opinion was considered overly precautionary in relation to both the displacement and mortality rates that were proposed, with these rates being higher than is considered to be justified on the basis of the available evidence (even when allowing for the incorporation of precaution in the assessment - volume 3, appendix 11.4, annex G of the Offshore EIA Report). Furthermore, the mortality rates advocated by the Scoping Opinion represented a marked change from the assumptions applied in assessments for other recent Scottish offshore wind farms (Marine Scotland 2017a,b,c) with no clear evidence apparently being available to justify such a change.
    2. Based upon a consideration of the available evidence for guillemot displacement, the potential consequent mortality, previous precedent and a need to incorporate precaution within the assessment, an alternative Developer Approach to estimating displacement effects was determined (volume 3, appendix 11.4, annex G of the Offshore EIA Report). The rates adopted by the Developer Approach are:
  • Breeding period: 50% displacement with a mortality rate of 1%.
  • Non-breeding period: 50% displacement with a mortality rate of 1%.
    1. Estimates of guillemot mortality were produced using the SNCB matrix on the basis of both the Scoping Approach and the Developer Approach (Offshore EIA Report, volume 3, appendix 11.4), with these estimates then apportioned to the Farne Islands SPA guillemot population during the breeding and non-breeding periods according to the MS Apportioning Tool (Butler et al. 2020) and the NatureScot (2018) approach, respectively (Offshore EIA Report, volume 3, appendix 11.5, Table 5.118). 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 Farne Islands SPA guillemot PVAs in this assessment (Offshore EIA Report, volume 3, appendix 11.6). Based on advice provided by NatureScot and Marine Scotland Science following Roadmap Meeting 4 (G. Holland, email 26/01/2022), it was also assumed that 7% of the breeding adults in the SPA population miss breeding in any given year (i.e. sabbatical birds) so that the number of estimated adult deaths during the breeding season was adjusted accordingly.

 

Table 5.118:
The Mean Peak Abundance Estimates of Guillemot in the Proposed Development Array Area and 2 km Buffer for each Seasonal Period, Together with the Proportion of Birds Estimated to Belong to the Breeding Adult Age Class and to be from the Farne Islands SPA Population in Each Period. The proportion of Adults Assumed to be Sabbaticals During the Breeding Season is also Presented

Table 5.118: The Mean Peak Abundance Estimates of Guillemot in the Proposed Development Array Area and 2 km Buffer for each Seasonal Period, Together with the Proportion of Birds Estimated to Belong to the Breeding Adult Age Class and to be from the Farne Islands SPA Population in Each Period. The proportion of Adults Assumed to be Sabbaticals During the Breeding Season is also Presented

 

  1. Based upon the estimates and assumptions detailed above, the potential annual mortality amongst the SPA guillemot population as a result of displacement is estimated as 80 adult and 89 immature birds based on the lower mortality rates for the Scoping Approach (i.e. Scoping Approach A) and as 168 adult and 185 immature birds based upon the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B) (Table 5.119). The breeding season effects make the greatest contribution to these potential mortalities (comprising 68% and 54% of the total annual mortality for the lower and upper ranges, respectively) due to the larger mean peak population size and higher assumed mortality rates during this period (although the proportion of birds assumed to derive from the SPA population is substantially higher during the non-breeding period) (Table 5.119).
  2. The annual mortality from displacement as determined using the Developer Approach is predicted to be 37 adult and 40 immature birds, equating to approximately 46% and 21% of the mortality predicted for the lower and upper range of the Scoping Approach, respectively (Table 5.119). In contrast to the Scoping Approach, the levels of predicted mortality are lower during the breeding season than during the non-breeding period, with the difference between the Developer and Scoping Approaches in this respect being due to the fact that the Developer Approach assumes the same mortality rates in each seasonal period.

 

Table 5.119:
Estimated Potential Annual Mortality of Farne Islands SPA Guillemots as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach

Table 5.119 Estimated Potential Annual Mortality of Farne Islands SPA Guillemots as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach

 

  1. The additional annual mortality of adult guillemot from the Farne Islands SPA population predicted due to displacement from the Proposed Development array represents 0.04% of the current adult breeding population at this colony (i.e. 85,816 individuals – Table 3.3 in the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and between approximately 0.09 – 0.20% of this population as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.073 – see Table 2.9 in the Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult mortality equate to an increase of 0.6% for the Developer Approach and of 1.3 – 2.7% for the lower and upper estimates from the Scoping Approach.
  2. The potential levels of impact on the Farne Islands SPA guillemot population resulting from the mortality predicted from displacement and barrier effects associated with the Proposed Development array during the operation and maintenance phase are considered in more detail below in the Project Alone: Population-Level Impacts section. This presents the outputs from PVAs of the potential effects of predicted displacement mortality on the SPA population.
Changes to prey availability
  1. Potential impacts on key prey species for guillemots breeding at Farne Islands SPA during the operation and maintenance phase have been assessed in volume 2, chapter 9 of the Offshore EIA Report using the appropriate maximum design scenarios for these receptors. Reduction or disruption to prey availability through temporary and long-term subtidal habitat loss/disturbance, increased SSC and deposition, reductions in water clarity, EMF from subsea electrical cabling, and colonisation of subsea structures, could affect guillemot survival and productivity in the Farne Islands SPA population.
  2. The same evidence basis and context in relation to this effect pathway for the operation and maintenance phase applies to the Farne Islands SPA guillemot population as to the St Abb’s Head to Fast Castle SPA guillemot population. This is detailed in the section on Project Alone: Operation and Maintenance – Changes to Prey Availability for the St Abb’s Head to Fast Castle SPA population.
  3. Given this, it is considered that there is relatively little potential for the Farne Islands SPA guillemot population to be affected by changes to prey availability during the operation and maintenance phase, with any such effects being largely intermittent across a relatively small spatial extent. Consequently, it is considered that there is no potential for operational or maintenance related changes in prey availability to lead to an adverse effect on the Farne Islands SPA guillemot 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 Farne Islands SPA guillemot population are limited to displacement (inclusive of barrier effects) during the operation and maintenance phase. For other effect pathways, there is considered to be no potential for an adverse effect on this population as a result of the Proposed Development alone, with any such effects likely to be small and of little, or no, consequence in terms of impacts at the population level.
  2. Given this, PVA was undertaken on the mortality to the adult and immature age classes predicted due to the displacement effects associated with the Proposed Development, as determined by both the Scoping and Developer Approaches (see Table 5.118 above). The population model for the SPA population was a stochastic, density independent, matrix model, based upon the demographic parameters specified in Table 2.9 of the Offshore EIA Report, volume 3, appendix 11.6. The starting population size was the 2019 count for the SPA, with the projected population trends considered over a 35 year timescale (Offshore EIA Report, volume 3, appendix 11.5). The approach and methods to undertaking the PVA are as described in the section on Project Alone: Population-Level Impacts for the St Abb’s to Fast Castle SPA kittiwake population above (with further details provided in the Offshore EIA Report, volume 3, appendix 11.6).
  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 5.120:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Farne Islands SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development Alone

Table 5.120: Projected 35 Year Population Sizes and Associated PVA Metrics for the Farne Islands SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development Alone

 

  1. The PVA predicted that the Farne Islands SPA guillemot population would increase over the 35 year projection period irrespective of the effects from the Proposed Development. Thus, the population is predicted to be approximately four times larger than the current estimate of 85,816 adult birds under all scenarios, including the baseline which assumes no wind farm effects (Table 5.120). Although the predicted increases in population size are inevitably greatest for the baseline scenario (because the PVAs are based on density independent models, which assume all mortality from the wind farm effects is additive and that there are no compensatory mechanisms operating within the population), the differences with the impact scenarios are small. Whilst the predicted levels of increase are unlikely to occur in reality (and are, in part, a consequence of the absence of any compensatory density dependence within the models – as discussed in the section on Project Alone: Population-level impacts for the St Abb’s Head to Fast Castle SPA kittiwake population), the prediction for an increasing trend is consistent with the documented long-term trend for this SPA population (see above).
  2. The PVA metrics suggest small effects overall. Thus, the CPS value for the Developer Approach indicates that the displacement effects from the Proposed Development alone would result in a reduction of less than 2% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects, whilst for the Scoping Approach the CPS values indicate reductions of 4 – 8% after 35 years, relative to that in the absence of any wind farm effects (Table 5.120). The associated reduction in annual population growth rate (relative to that predicted under baseline conditions) is not detectable (at least when the CPGR value is expressed to three decimal places) for the Developer Approach and is 0.1 – 0.2% for the Scoping Approach. The centile values indicate considerable overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, at least a reasonably high likelihood of the impacted population being of a similar size to the un-impacted population after 35 years (Table 5.120).
  3.  For the same reasons as described in the section on Project-Alone: Population-Level Impacts for the St Abb’s Head to Fast Castle SPA guillemot population, the assessment of the Farne Islands SPA guillemot population incorporates high levels of precaution, which extend beyond the differences between the Developer and Scoping Approaches that are outlined above (and detailed in the Offshore EIA Report, volume 3, appendix 11.4). Notably, the concerns over the extent to which the seasonal mean peak abundances (which provide the basis for the displacement mortality estimates) are likely to be representative of the overall usage of the Proposed Development array and two kilometre buffer by guillemot are equally relevant to the Farne Islands SPA population as to the St Abb’s Head to Fast Castle SPA population. The evidence available from tracking data suggests that levels of usage of the Proposed Development array area and two kilometre buffer during the breeding season by guillemots from the Farne Islands SPA are likely to be low (Wakefield et al. 2017).
Project alone: conclusion
  1. It is considered that the predicted levels of impact from the Proposed Development alone on the Farne Islands SPA guillemot population are of a relatively small scale, as determined by both the Developer and Scoping Approaches. For both the Developer and Scoping Approaches it is also the case that the centile metric indicates at least a reasonably high likelihood of the impacted population being of similar size to the un-impacted population after 35 years. These levels of impact are within the context of an assessment which incorporates high levels of precaution (particularly as determined by the Scoping Approach) and a population for which the documented, long-term, trend is strongly increasing. Given this, it is concluded that the effects from the Proposed Development alone (as determined by either the Developer or Scoping Approaches) would not result in an adverse effect on this SPA population.
Effects in-combination
Effects of relevance to the in-combination assessment
  1. As detailed above, any effects from the Proposed Development alone on the Farne Islands SPA guillemot population during construction and decommissioning and resulting from disturbance and changes to prey availability during operation and maintenance will be small and highly localised. As such, there is considered to be no potential for these effect pathways to add to impacts at the population-level that might result from other effects pathways associated with the Proposed Development or from the effects due to other plans and projects.
  2. Therefore, the potential for effects of the Proposed Development to act on the Farne Islands SPA guillemot population in-combination with other plans and projects is limited to the displacement (inclusive of barrier effects) pathway during operation and maintenance.
  3. As for other SPA populations, consideration was given to the potential displacement mortality associated with the Proposed Development in-combination with the other UK North Sea wind farms. However, none of these other wind farms were identified as contributing to either the breeding or non-breeding season effects on the Farne Islands SPA guillemot population. This is unsurprising, given the considerable distance of this SPA to most other North Sea wind farms, together with the fact that during the non-breeding season the potential for effects was also assumed to be limited to those plans and projects which are within the breeding season foraging range of the guillemot SPA population (as advised by the Scoping Opinion – volume 3, appendix 6.2 of the Offshore EIA Report).
In-combination: conclusion
  1. Based on the above, the effects from the Proposed Development in-combination with the other UK North Sea wind farms are equivalent to those from the Proposed Development alone. Consequently, it is concluded that the effects from the Proposed Development in-combination with the other UK North Sea wind farms would not result in an adverse effect on the Farne Islands SPA guillemot population. This conclusion applies to both the Scoping and Developer Approaches.

Assessment for the razorbill population

  1. The Farne Islands SPA razorbill population is currently estimated to number 572 individuals, based upon the most recently available count data from 2019 (Offshore EIA Report, volume 3, appendix 11.5). This small SPA population has increased over the long term, with the population estimated as only 62 AOSs in 1986 (which would be expected to equate to 124 individuals) (SMP 2022). Numbers appear to have been relatively stable since 2005, albeit with some marked between-year fluctuations (with the annual population size varying from 421 to 677 between 2005 and 2019[16]).
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 Farne Islands SPA, so that potential impacts on its razorbill population will only occur as a result of individuals from the colony occurring in the area (or vicinity) of the Proposed Development. Consequently, the main focus of the assessment for this SPA population is concerned with the Conservation Objective of maintaining or restoring the populations of each qualifying feature, because the other conservation objectives either apply to the site itself, and not to areas beyond the boundary, or are encompassed by the assessment of this Conservation Objective (as for maintaining or restoring the structure and function of the habitats of the qualifying features, because habitat structure and function would only be considered significant if it caused an adverse effect on the maintenance or restoration of the population of the qualifying features). In terms of the SACOs, this focus is most closely reflected in the attributes concerned with the abundance and diversity of the species assemblage which have the targets of maintaining; (i) the abundance of the breeding seabird assemblage qualifying feature at a level above 163,819 individuals, whilst avoiding deterioration from its current levels; and (ii) the species diversity of the breeding seabird assemblage qualifying feature.
  2. From published information on razorbill foraging ranges generally (Woodward et al. 2019) and evidence from tracking data (Wakefield et al. 2017), it is possible that during the breeding period razorbills from the Farne Islands SPA occur within the area of the Proposed Development and of the two km buffer around the Proposed Development array area. This is supported by the findings of the apportioning exercise, which estimates that approximately 0.4% 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 the NatureScot scoping advice (volume 3, appendix 6.2 of the Offshore EIA Report), which draws upon the findings from Buckingham et al. (2022), razorbills are assumed to disperse more widely than guillemots during the non-breeding period, with their distribution concentrated in central areas of the North Sea during the mid-winter period. Consequently, it is assumed (for the purposes of the assessment) that during the non-breeding period birds from the Farne Islands 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 Farne Islands SPA razorbill population during breeding and non-breeding periods.
Project alone: construction and decommissioning
Disturbance
  1. Direct disturbance to razorbills 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), razorbills are considered to have a moderate sensitivity to such sources of direct disturbance. Thus, reviews of the sensitivity of different seabird species to disturbance from vessels and helicopter traffic assign razorbill as ‘3’ on a five-scale ranking system, where 1 indicates hardly any or limited escape/avoidance behaviour and very short flight distance when approached and 5 indicates strong escape/avoidance behaviour and a large response distance (Garthe and Hüppop 2004, Furness et al. 2013).
  4. The total area to be affected by such disturbance over the full eight years of the construction phase also represents a small proportion of the total area of marine habitat available to razorbills from the Farne Islands 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 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. Similarly, the Proposed Development array and export cable corridor represent approximately 10% of the breeding season foraging area if considering the mean maximum foraging range only.
  5. Tracking data (and associated modelling of foraging distributions) for razorbill suggest that the Proposed Development array area and Proposed Development export cable corridor are beyond waters that are heavily used by birds from the Farne Islands SPA during the breeding season (Wakefield et al. 2017).
  6. 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.
  7. 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.
  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 moderate sensitivity of razorbill to disturbance effects, the relatively small areas that will be subject to activities with the potential to result in disturbance at any given time during the construction period and the fact that these potential effects will be temporary, it is considered that there is no potential for construction or decommissioning related disturbance to lead to an adverse effect on the Farne Islands 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 Farne Islands SPA razorbill population and be limited to, at most, an eight year period during construction (and a likely similar or shorter period during decommissioning). Furthermore, as detailed above, potential effects of disturbance will not occur simultaneously across the entirety of the Proposed Development array area or Proposed Development export cable corridor but, rather, will be carried out in different areas at different times. Thus, at any given time the potential for disturbance effects that could lead to displacement of razorbills from this SPA will be limited to relatively small areas, with the potential effects also being of a temporary nature.
  2. Based upon the above, it is considered that there is relatively little potential for the Farne Islands SPA razorbill population to be affected by displacement during the construction or decommissioning phases, with any such effects only extending across relatively small areas and tending to be temporary in nature. Consequently, it is considered that there is no potential for construction or decommissioning related displacement to lead to an adverse effect on the Farne Islands 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 Farne Islands 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 kittiwake population. The evidence base and context for assessing the potential for such effects to have impacts on the Farne Islands SPA razorbill population are as for the St Abb’s Head to Fast Castle SPA razorbill population (and are detailed above in the equivalent section for that SPA population).
  3. Given this, it is considered that there is relatively little potential for the Farne Islands 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 Farne Islands 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 Farne Islands SPA. As described in the section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population, razorbills are considered to have a moderate sensitivity to such sources of direct disturbance at sea (Garthe and Hüppop 2004, Furness et al., 2013).
  2. The maximum design scenario is for up to 3,393 vessel round trips per year over the operational lifetime of the project. Vessel types which will be required during the operation and maintenance phase include those used during routine inspections, repairs and replacement of equipment, major component replacement, painting or other coatings, removal of marine growth, replacement of access ladders, and geophysical surveys (Table 4.1).
  3. Based on information presented in the section on Project Alone: Operation and Maintenance – Disturbance for the St Abb’s Head to Fast Castle SPA kittiwake population and in the Offshore EIA Report, volume 2, chapter 13, baseline levels of vessel traffic in the Offshore Ornithology study area are relatively high. In the context of the baseline levels of vessel traffic across the Offshore Ornithology study area, the increase during the operation and maintenance phase is considered to be relatively small. Vessel movements will be within the Proposed Development array area and export cable corridor and will follow existing shipping routes to/from ports. In addition, Project Codes of Conduct included as a part of the NSVMP (Offshore EIA Report, volume 4, appendix 25) will be issued to all project vessel operators to avoid sudden changes in course or speed which will minimise the potential for disturbance. Within the Proposed Development array area, movements and associated maintenance activities will be restricted to individual wind turbines over a period of days to weeks.
  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 Farne Islands SPA razorbill population.
Displacement/barrier effects
  1. As outlined above, displacement effects on the Farne Islands 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 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 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. As with other species for which displacement effects are assessed (see above), 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, with these rates being higher than is considered to be justified on the basis of the available evidence (even when allowing for the incorporation of precaution in the assessment - volume 3, appendix 11.4, annex G of the Offshore EIA Report). Furthermore, the mortality rates advocated by the Scoping Opinion represented a marked change from the assumptions applied in assessments for other recent Scottish offshore wind farms (Marine Scotland 2017a,b,c) with no clear evidence apparently being available to justify such a change.
    2. Based upon a consideration of the available evidence for 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 (volume 3, appendix 11.4, annex G of the Offshore EIA Report). The rates adopted by the Developer Approach are:
  • Breeding period: 50% displacement with a mortality rate of 1%.
  • Non-breeding period: 50% displacement with a mortality rate of 1%.
    1. Estimates of 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 Farne Islands 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, Table 5.121). The resulting mortality estimates for the breeding period were apportioned to age classes on the basis of the asymptotic age distribution of the population model used for the Farne Islands SPA razorbill PVAs in this assessment (Offshore EIA Report, volume 3, appendix 11.6). Based on advice provided by NatureScot and Marine Scotland Science following Roadmap Meeting 4 (G. Holland, email 26/01/2022), it was also assumed that 7% of the breeding adults in the SPA population miss breeding in any given year (i.e. sabbatical birds) so that the number of estimated adult deaths during the breeding season was adjusted accordingly.

 

Table 5.121:
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 Farne Islands SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals During the Breeding Season is also Presented

Table 5.121: 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 Farne Islands SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals During the Breeding Season is also Presented

 

  1. Based upon the estimates and assumptions detailed above, the potential annual mortality amongst the SPA razorbill population as a result of displacement is estimated as a single individual (adults and immatures combined) as determined by the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B), and as only fractions of an individual as determined by the lower mortality rates of the Scoping Approach and by the Developer Approach (Table 5.122). These small effects are attributable to both the breeding and non-breeding periods.

 

Table 5.122:
Estimated Potential Annual Mortality of Farne Islands 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 5.122: Estimated Potential Annual Mortality of Farne Islands SPA Razorbills as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach

 

  1. The additional annual mortality of adult razorbill from the Farne Islands SPA population predicted due to displacement from the Proposed Development array represents 0.02% of the current adult breeding population at this colony (i.e. 572 individuals – Table 3.3 in the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and between approximately 0.03 – 0.09% of this population as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.090 – see Table 2.19 in volume 3, appendix 11.6 of the Offshore EIA Report), the estimates of adult mortality equate to an increase of 0.2% for the Developer Approach and of 0.4 – 1.0% for the lower and upper estimates from the Scoping Approach.
  2. The potential levels of impact on the Farne Islands 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.
Changes to prey availability
  1. Potential impacts on key prey species for razorbills breeding at Farne Islands SPA during the operation and maintenance phase have been assessed in volume 2, chapter 9 of the Offshore EIA Report using the appropriate maximum design scenarios for these receptors. Reduction or disruption to prey availability through temporary and long-term subtidal habitat loss/disturbance, increased SSC and deposition, reductions in water clarity, EMF from subsea electrical cabling, and colonisation of subsea structures, could affect razorbill survival and productivity in the Farne Islands SPA population.
  2. The same evidence basis and context in relation to this effect pathway for the operation and maintenance phase applies to the Farne Islands SPA razorbill population as to the St Abb’s Head to Fast Castle SPA razorbill 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 Farne Islands SPA razorbill 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 Farne Islands SPA razorbill population.