Assessment for the Non-breeding Waterfowl Assemblage

  1. The non-breeding waterfowl assemblage for the Outer Firth of Forth and St Andrews Bay Complex SPA is a qualifying feature on the basis of the SPA supporting in excess of 20,000 individual waterbirds. Eider, velvet scoter, common scoter, goldeneye, red-breasted merganser and long-tailed duck are amongst the species identified in the citation as having nationally important populations which contribute to SPA non-breeding waterbird assemblage.
  2. Potential impacts of the Proposed Development alone and in-combination with either the other Forth and Tay or the other UK North Sea wind farms on the non-breeding waterfowl assemblage for the SPA could arise via effects on the individual species within the assemblage feature.
  3. The assessment undertaken for each qualifying feature identifies no potential adverse effects on any of the component species from the project alone or in-combination.  Consequently, it is concluded that there will not be an adverse effect on the Outer Firth of Forth and St Andrews Bay Complex SPA non-breeding waterfowl assemblage, in relation to the Proposed Development in-combination with (i) the other Forth and Tay wind farms and (ii) the other UK North Sea wind farms.

Assessment for the Breeding Seabird Assemblage

  1. The breeding seabird assemblage for the Outer Firth of Forth and St Andrews Bay Complex SPA is a qualifying feature on the basis of the SPA supporting in excess of 20,000 individual seabirds. Puffin, kittiwake, Manx shearwater, guillemot and herring gull are species identified in the citation as having nationally important populations which contribute to the Outer Firth of Forth and St Andrews Bay Complex SPA breeding seabird assemblage.
  2. Potential impacts of the Proposed Development alone and in-combination with either the other Forth and Tay or the other UK North Sea wind farms on the breeding seabird assemblage for the SPA could arise via effects on the individual species within the assemblage feature. The assessments undertaken identify the potential for adverse effects from the Proposed Development alone on the SPA kittiwake population. There is potential for adverse in-combination effects on the SPA kittiwake population and, based on the Scoping approach, also to guillemot, and puffin populations
  3. Given the above, it is concluded that there is the potential for an adverse effect on the Outer Firth of Forth and St Andrews Bay Complex SPA breeding seabird assemblage, in relation to the Proposed Development in-combination with (i) the other Forth and Tay wind farms and (ii) the other UK North Sea wind farms. This conclusion applies to the assessments undertaken according to both the Developer Approach and the Scoping Approach.

Assessment for the Non-breeding Seabird Assemblage

  1. The non-breeding seabird assemblage for the Outer Firth of Forth and St Andrews Bay Complex SPA is a qualifying feature on the basis of the SPA supporting in excess of 20,000 individual seabirds. Black-headed, common and herring gulls, along with kittiwake, guillemot, razorbill and shag are the species identified in the citation as having nationally important populations which contribute to SPA non-breeding seabird assemblage.
  2. Potential impacts of the Proposed Development alone and in-combination with either the other Forth and Tay or the other UK North Sea wind farms on the non-breeding seabird assemblage for the SPA could arise via effects on the individual species within the assemblage feature.
  3. The assessment undertaken for each qualifying feature identifies no potential adverse effects on any of the component species from the project alone or in-combination.  Consequently, it is concluded that there will not be an adverse effect on the Outer Firth of Forth and St Andrews Bay Complex SPA non-breeding seabird assemblage, in relation to the Proposed Development in-combination with (i) the other Forth and Tay wind farms and (ii) the other UK North Sea wind farms.

Site Conclusion

  1. It is concluded that the possibility of adverse effects cannot be discounted for the Outer Firth of Forth and St. Andrews Bay Complex SPA given the potential for impacts on breeding kittiwake, guillemot and puffin at functionally-linked SPAs. For the kittiwake and guillemot populations, the potential for adverse effects arises from the Proposed Development alone and in-combination with either (i) the other Forth and Tay wind farms or (ii) the other UK North Sea wind farms. For the puffin population, the potential for an adverse effect is in-combination with either (i) the other Forth and Tay wind farms or (ii) the other UK North Sea wind farms (but not to the effects of the Proposed Development alone). The potential for an adverse effect on Outer Firth of Forth and St. Andrews Bay Complex SPA is a direct consequence of the potential effects on these breeding SPA populations, which are assessed separately below.
  2. Consequently, it is concluded that an Adverse Effects on Integrity of the Outer Firth of Forth and St. Andrews Bay Complex SPA cannot be excluded.

 

5.7. Appropriate Assessments: Breeding Seabird Colony SPAs

5.7.1.    St Abb’s Head to Fast Castle SPA

European site information and conservation objectives

  1. The St Abb’s Head to Fast Castle SPA is located on the Berwickshire coast in southeast Scotland, at approximately 32 km from the Proposed Development array area and 4 km from the Proposed Development export cable corridor. The SPA was designated in 1997 and comprises an area of sea cliffs and coastal strip along which there are multiple seabird colonies, with a seaward extension which extends approximately 1 km into the marine environment.
  2. There are no Annex I qualifying features and the site qualifies under Article 4.2 by regularly supporting in excess of 20,000 individual seabirds, with the breeding seabird assemblage feature including five named component species (Table 5.18). The potential for LSE has been identified in relation to four of these five named components (Table 5.18), with the effect pathways associated with LSE for each of these detailed in Table 3.1 and set out in the assessment below.
  3. The conservation objectives of this SPA (as determined from NatureScot’s SiteLink (SiteLink (nature.scot)) are:
  • To avoid deterioration of the habitats of the qualifying species (listed below) or significant disturbance to the qualifying species, thus ensuring that the integrity of the site is maintained; and
  • To ensure for the qualifying species that the following are maintained in the long term:

–           Population of the species as a viable component of the site;

–           Distribution of the species within site;

–           Distribution and extent of habitats supporting the species;

–           Structure, function and supporting processes of habitats supporting the species; and

–           No significant disturbance of the species.

  1. Further information on this European site is presented in appendix 3A.

 

Table 5.18:
Details on the Qualifying Features of the St Abb’s Head to Castle SPA

Table 5.18: Details on the Qualifying Features of the St Abb’s Head to Castle SPA

*Named components of the assemblage only.

 

Assessment for the kittiwake population

  1. The St Abb’s Head to Fast Castle SPA kittiwake population is currently estimated to number 5,452 breeding pairs and has been declining since the SPA was designated. The whole SPA has only been counted sporadically since 1985, most recently in 2016 to 2020, but the main colony in the SPA (the St Abb’s Head NNR, which comprises approximately 85% of the current SPA population) is counted annually. The population size has been below the citation population size in all years for which count data are available since 1987 (Figure 5.13). The more recent counts provide a tentative indication that there may be some stabilisation in the SPA population size, albeit at a level well below the citation size.

Figure 513:
Kittiwake Population Trend at the St Abb’s Head NNR Between 1986 and 2021, with Three Counts for the Entire St Abb’s Head to Fast Castle SPA also Shown (Noting that the Latest SPA Count is Shown for 2018 Because it Spans the Period 2016 – 2020). The Red Line Shows the Citation Population Size for the SPA (21,170 pairs). Data are from the Seabird Monitoring Programme Database (Seabird Monitoring Programme | JNCC (bto.org)).

Figure 513: Kittiwake Population Trend at the St Abb’s Head NNR Between 1986 and 2021, with Three Counts for the Entire St Abb’s Head to Fast Castle SPA also Shown (Noting that the Latest SPA Count is Shown for 2018 Because it Spans the Period 2016 – 2020). The Red Line Shows the Citation Population Size for the SPA (21,170 pairs). Data are from the Seabird Monitoring Programme Database (Seabird Monitoring Programme | JNCC (bto.org)).

The potential for impacts on the kittiwake population
  1. The Proposed Development and two kilometre buffer around the Proposed Development array area[7] do not overlap with the St Abb’s Head to Fast Castle SPA, so that potential impacts on its kittiwake 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 kittiwake foraging ranges generally (Woodward et al. 2019) and tracking from the SPA specifically (Wakefield et al. 2017, Bogdanova et al. 2022), it is apparent that during the breeding period kittiwakes from the St Abb’s Head to Fast Castle SPA occur within the area of the Proposed Development and of the two km buffer around the Proposed Development Array area. This is reflected in the findings of the apportioning exercise, which estimates that approximately 52% of the kittiwakes 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 kittiwake is defined as mid-April to August, following the NatureScot (2020) guidance.
  3. In the non-breeding season kittiwakes are largely pelagic, with birds from some UK colonies wintering as far west as the coast of eastern Canada (Frederiksen et al. 2012), although most of those which breed on the North Sea coast likely winter in the North Sea and Celtic Sea. Therefore, it is likely that there is the potential for birds from the St Abb’s Head to Fast Castle SPA population to pass through offshore wind farms in the North Sea during the autumn and spring passage periods (defined as September to December and January to mid-April, respectively, on the basis of applying the BDMPS defined periods within the context of the overall non-breeding period defined by NatureScot – Furness 2015, NatureScot 2020, Offshore EIA Report, volume 3, appendix 11.4). Given the above, the Proposed Development may have potential effects on the St Abb’s Head to Fast Castle SPA kittiwake population during breeding and non-breeding periods.
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 St Abb’s Head to Fast Castle SPA. Thus, the Proposed Development array area encompasses 1,010 km2, whilst the Proposed Development export cable encompasses 168 km2. Together these areas represent 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 show that the Proposed Development array area and Proposed Development offshore export cable corridor overlap with, or occur close to, waters that are heavily used by birds from the St Abb’s Head to Fast Castle SPA during the breeding season (Cleasby et al. 2018, Bogdanova et al. 2022). However, the degree of overlap is limited and excludes those areas of heaviest usage. For example, based on the data from 37 birds tracked from this SPA population during the 2021 breeding season, there is no overlap between the Proposed Development array area and either the core foraging or ‘resting at sea’ areas of the tracked birds (as defined by the respective 50% utilisation distributions), whilst only 20% of the wider foraging and ‘resting at sea’ areas (as defined by the 90% utilisation distribution) overlap with the Proposed Development array area (Bogdanova et al. 2022). Furthermore, during the 2021 work, only 11% of the tracked birds and 3% of the total tracks passed through the Proposed Development array area.
  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) and the potential for effects of construction-related disturbance is lower than during the breeding season.
  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 relatively small areas that will be subject to activities with the potential to result in disturbance at any given time during the construction period and the fact that these potential effects will be temporary, it is considered that there is no potential for construction or decommissioning related disturbance to lead to an adverse effect on the St Abb’s to Fast Castle SPA 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 St Abb’s Head to Fast Castle 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 St Abb’s Head to Fast Castle 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 St Abb’s to Fast Castle 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 St. Abb’s Head to Fast Castle SPA kittiwake population in the short-term.
  2. During construction there are a number of ways in which effects on key prey species may occur. The installation of infrastructure within the Proposed Development may lead to temporary subtidal habitat loss/disturbance as a result of a range of activities including use of jack-up vessels during foundation installation, installation of inter-array, interconnector and offshore export cables and associated seabed preparation, and anchor placements associated with these activities. There is the potential for temporary habitat loss/disturbance to affect up to 113,974,700 m2 of seabed during the construction phase, which equates to 9.7% of the Proposed Development area. Activities will occur intermittently during the construction phase, with only a small proportion of the total footprint affected at any one time. Recovery of seabed habitats will commence immediately following installation of infrastructure allowing key prey species to repopulate the areas of previous disturbance (see volume 2, chapter 9 of the Offshore EIA Report). On this basis, temporary habitat loss/disturbance to key prey species during the construction phase was assessed as being of low magnitude in volume 2, chapter 9 of the Offshore EIA Report.
  3. In addition to temporary habitat loss/disturbance for key prey species, construction activities are also predicted to result in long-term subtidal habitat loss through the installation of foundations and associated scour protection, cable protection, OSP/Offshore Convertor Station Platform interconnector and offshore export cables. Up to 7,798,856 m2 of long-term subtidal habitat loss is predicted. Many species of fish are reliant upon the presence of suitable subtidal habitat for foraging, spawning and nursing. However, these areas of habitat loss will be discrete, either in the immediate vicinity of foundations (i.e. foundations and scour protection), or relatively small isolated stretches of cable within large areas of sediment which characterise the baseline environment (i.e. soft sediments), representing a very low proportion of available habitat (0.7% of the Proposed Development fish and shellfish ecology study area). Long-term subtidal habitat loss to key prey species during the construction phase was therefore assessed as being of low magnitude in volume 2, chapter 9 of the Offshore EIA Report.
  4. Increases in SSC and associated sediment deposition may also reduce the abundance and distribution of fish. The installation of all wind turbines and offshore substation foundations and the installation of inter-array, interconnector and offshore export cables may result in short-term avoidance of affected areas by fish. The maximum design scenario assessed in volume 2, chapter 9 of the Offshore EIA Report assumed all wind turbine and offshore substation foundations will be installed by drilling 5.5 m diameter piles and installation of inter-array cables through jet-trenching. Modelling of SSCs showed that the plume directly associated with foundation installation was < 5 mg/l, dropping to lower levels within a very short distance, typically < 500 m. Modelling of SSC for installation of inter-array and offshore export cables indicated concentrations of up to 500 mg/l and between 50 mg/l and 500 mg/l, respectively. Adult fish have high mobility and may show avoidance behaviour in areas of high sedimentation. However, there may be impacts on the hatching success of fish larvae and consequential effects on the viability of spawning stocks due to limited mobility. Spawning grounds for sandeel overlap with the Proposed Development fish and shellfish ecology study area, and their eggs are buried in the seabed for couple of weeks before hatching. Sandeel eggs are known to be tolerant to sediment deposition due to the nature of re-suspension and deposition within their natural high energy environment, and it is therefore very likely that any effect from increased SSC during construction will be limited. Herring spawning grounds are also found within the Proposed Development fish and shellfish ecology study area, with their eggs potentially tolerant of very high levels of SSC (volume 2, chapter 9 of the Offshore EIA Report). Furthermore, deposited sediments are expected to be removed quickly by the currents resulting in small amount of sediment being deposited. Given the small amount of predicted deposition, local spatial extent and relatively short duration of predicted SSC increases, no effect on survival of these key prey species was predicted by volume 2, chapter 9 of the Offshore EIA Report.
  5. Increases in SSC and associated reductions in water clarity may also affect the ability of foraging kittiwakes to locate fish at the sea surface, reducing the availability of key prey species. However, it is considered that foraging kittiwakes from the St. Abb’s Head to Fast Castle SPA will be largely unaffected by the low-level temporary increases in SSC, as the concentrations are likely to be within the range of natural variability (generally <5 mg/l but can increase to over 100 mg/l during storm events/increased wave heights) and will reduce to background concentrations within a very short period (approximately two tidal cycles).
  6. There is the potential for underwater noise and vibration during construction pile-driving to affect the abundance and distribution of kittiwake prey (see volume 2, chapter 9 of the Offshore EIA Report). Injury and/or mortality for all fish species is to be expected for individuals within very close proximity to piling operations. However, this is unlikely to result in significant mortality due to the implementation of soft starts during piling operations which will allow fish to move away from the areas of highest noise levels, before the received noise reaches a level that would cause an injury. Although spawning and nursery habitats for key prey species are present within the zone of influence of underwater noise from piling, these habitats extend over a very wide area across the Proposed Development fish and shellfish ecology study area. The relative proportion of these habitats affected by piling operations at any one time will therefore be small in the context of the wider habitat available. The potential onset of behavioural effects which could affect the distribution of key prey species (such as elicitation of a startle response, disruption of feeding, or avoidance of an area) may occur to ranges of approximately 17 km to 23 km (see volume 2, chapter 9 of the Offshore EIA Report). However, evidence from Beatrice Offshore Wind Farm (BOWL, 2021a, 2021b) has demonstrated that noise impacts on fish behaviour associated with piling are temporary and that fish communities (including sandeel) show a high degree of recoverability following construction (see also RPS, 2019). Furthermore, the Proposed Development array area and export cables corridor represent less than 1% of the total breeding season foraging area that is potentially available to the SPA kittiwake population, as defined by the species’ mean-maximum breeding season foraging range plus 1 SD (i.e.156.1±144.5 km; Woodward et al., 2019). Non-breeding season effects are considered to be lower than during the breeding season given that birds are no longer constrained by the location of their colonies and are likely to occur across large expanses of sea (Frederiksen et al., 2012; Furness 2015).
  7. During decommissioning, the effects from changes in prey availability are considered to be the same (or less) as for construction. It is currently unclear as to how the presence, and subsequent removal of, subsea structures may affect kittiwake prey species (Peschko et al., 2020; BOWL 2021a, b; Scott, 2022). It is possible that prey abundance could decline from the levels present during the operation and maintenance period. This could occur if the sub-surface structures associated with the Proposed Development in the marine environment lead to an increase in key prey abundance within the Proposed Development array area and export cable corridor via the provision of artificial reef habitats. However, some infrastructure (such as scour and cable protection) is assumed to be left in situ with the impact of colonisation of infrastructure continuing in perpetuity following decommissioning. Thus, any reduction in prey abundance through removal of foundations is likely to be very small relative to the area over which breeding and non-breeding kittiwakes forage.
  8. Based upon the above, it is considered that there is relatively little potential for the St Abb’s Head to Fast Castle 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 St. Abb’s to Fast Castle SPA kittiwake population. This conclusion is consistent with the outcome of the EIA which concluded that effects from changes in prey availability on kittiwakes during construction and decommissioning were not significant in EIA terms (volume 2, chapter 11 of the Offshore EIA Report).
Project alone: operation and maintenance
Disturbance
  1. Vessel use within the Proposed Development array area and export cable corridor during the operation and maintenance phase may lead to direct disturbance of kittiwakes. 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).
  2. Based on information presented in the Offshore EIA Report, volume 2, chapter 13, baseline levels of vessel traffic in the Offshore Ornithology study area are relatively high. An average of 14 vessels per day were recorded within a 10 nm buffer around the Proposed Development array area (hereinafter Proposed Development shipping and navigation study area) over a 14-day survey period in August 2022. The vessel traffic surveys also showed an average of three to four vessels intersecting the Proposed Development array area per day over summer. Throughout the season, a maximum of 25 vessels were recorded within the Proposed Development array shipping and navigation study area over one day.
  3. 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 Navigational Safety and Vessel Management Plan (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.
  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 small) parts of these wider areas.
  5. Given the low sensitivity of kittiwake to disturbance effects at sea (Garthe and Hüppop 2004; Furness et al., 2013), the relatively small areas relative to the species’ foraging range that will be subject intermittently to potentially disturbing activities (Woodward et al., 2019), and the fact that these potential effects will be reduced compared to the construction and decommissioning phases, it is considered that there is no potential for disturbance during operation and maintenance to lead to an adverse effect on the St Abb’s to Fast Castle SPA 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/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, volume 3, appendix 11.4 of the Offshore EIA Report). Thus, throughout this section, mortality from displacement is assumed to refer to that which results from both displacement and barrier effects.
  2. Displacement mortality is calculated using the peak population size (using the counts of birds on the water plus those in flight) for each of the relevant seasonal periods, averaged over the two years of baseline survey, for the Proposed Development array area and two kilometre buffer volume 3, appendix 11.4 of the Offshore EIA Report, Table 5.19). A displacement rate is applied to each of the seasonally specific mean peak population sizes to estimate the numbers of displaced birds in each seasonal period, with an assumed mortality rate applied to those birds estimated to be displaced.
  3. 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:

 

Table 5.19:
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 St Abb’s Head To Fast Castle SPA Population in Each Period. The Proportion Of Adults Assumed to be Sabbaticals During The Breeding Season is also Presented

Table 5.19: 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 St Abb’s Head To Fast Castle SPA Population in Each Period. The Proportion Of Adults Assumed to be Sabbaticals During The Breeding Season is also Presented

 

  1. Based upon the estimates and assumptions detailed above, the potential annual mortality amongst the SPA kittiwake population as a result of displacement is estimated as 30 adult and 1 immature birds based on the lower mortality rates for the Scoping Approach (i.e. Scoping Approach A) and as 88 adult and 3 immature birds based upon the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B) (Table 5.20). As expected on the basis that kittiwakes from this breeding colony SPA use the waters within the vicinity of the Proposed Development array area during the breeding season (and as reflected by the seasonally-specific apportioning rates), the displacement effects predicted by the Scoping Approach are largely attributable to the breeding season (with the potential breeding season mortality accounting for c.97% of the overall annual mortality – Table 5.20).
  2. The annual mortality from displacement as determined using the Developer Approach is predicted to be 58 adult and 2 immature birds, so lies approximately midway between the mortality predictions from the Scoping Approach and is entirely attributable to breeding season effects (on the basis that displacement effects on kittiwake during the non-breeding periods are considered unlikely to result in detectable impacts on the population – volume 3, appendix 11.4, annex G of the Offshore EIA Report).

 

Table 5.20:
Estimated Potential Annual Mortality of St Abb’s Head to Fast Castle 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 5.20: Estimated Potential Annual Mortality of St Abb’s Head to Fast Castle 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 St Abb’s Head to Fast Castle SPA population predicted due to displacement from the Proposed Development array represents 0.5% of the current adult breeding population at this colony (i.e. 10,904 individuals – Table 3.3 in the Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach, and between approximately 0.3 – 0.8% of this population as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.145 – see Table 2.13 in the Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult mortality equate to an increase of 3.7% for the Developer Approach and of 1.9 – 5.6% for the lower and upper estimates from the Scoping Approach.
  2. The potential levels of impact on the St Abb’s Head to Fast Castle SPA 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, volume 3, appendix 11.3 of the Offshore EIA Report). 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. 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 (i.e. from at least the Round 3 and Scottish territorial waters leasing rounds onwards). 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. In part at least, this advice appeared to derive from a decision that it was not possible to use the stochastic version of the CRM (McGregor et al. 2018) due to an absence of recommended avoidance rates, meaning that the resultant collision estimates for the Proposed Development (as generated from the deterministic CRM) would not incorporate measures of associated variability[9]. However, the use of the maximum monthly densities does not actually address this issue, whilst alternative solutions to expressing the associated variability in the collision estimates exist and have been applied in other assessments (Natural England 2022a). Furthermore, it is also the case that guidance from Natural England accepts that option 2 of the stochastic CRM can be used with the same species-specific avoidance rates as for option 2 of the deterministic CRM (Natural England 2022a).
  3. Given that the approach advised in the Scoping Opinion for predicting collision mortality was considered overly precautionary (and did not follow previous precedent), the CRMs for kittiwake were undertaken following:

 

Table 5.21:
Predicted Collision Effects from The Proposed Development On The St Abb’s Head to Fast Castle SPA Kittiwake Population, As Determined by The Scoping Approach and Developer Approach. Estimates are for the Maximum Design Scenario and are Based on Option 2 of the Deterministic CRM Using A 98.9% Avoidance Rate (See Text)

Table 5.21: Predicted Collision Effects from The Proposed Development On The St Abb’s Head to Fast Castle SPA Kittiwake Population, As Determined by The Scoping Approach and Developer Approach. Estimates are for the Maximum Design Scenario and 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 St Abb’s Head to Fast Castle SPA population predicted due to collisions with wind turbines in the Proposed Development array represents approximately 1.8% of the number of adults currently estimated to breed at this colony (i.e. 10,904 individuals – Table 3.3 in Offshore EIA Report, volume 3, appendix 11.5) as determined by the Developer Approach and approximately 2.6% 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 Offshore EIA Report, volume 3, appendix 11.6), the predicted adult collision mortality equates to increases of 12.4% and 17.9% for the Developer and Scoping Approaches, respectively.
  2. The kittiwake collision estimates calculated using alternative assumptions are substantially lower than those on which this assessment is based. Thus, using the site-specific flight height data (as collected during a series of boat-based surveys of the Proposed Development array area) within the CRM gives annual collision estimates for kittiwake that are 8% and 33% of those derived using the generic flight height data of Johnston et al. (2014a,b), when using the laser range finder and visual flight height estimates, respectively (volume 3, appendices 11.3 and 11.7 of the Offshore EIA Report). Similarly, estimates derived using options 2 and 3 of the stochastic version of the CRM with the Bowgen and Cook (2018) avoidance rates applied are approximately 50% of the estimates on which the assessment is based (volume 3, appendix 11.3 of the Offshore EIA Report). Given that these differences are consistent across seasonal periods, these scales of reduction can be extrapolated directly to the collision estimates for the SPA population, meaning that the potential impacts (as expressed above in relation to the adult population size and the change to baseline adult mortality) would be reduced by at least 50% compared to those on which the assessment is based (according to either the Developer or Scoping Approaches).
  3. More detailed consideration of the potential population-level impacts associated with the predicted collision mortalities in Table 5.21 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 St. Abb’s Head to Fast Castle SPA during the operation and maintenance phase have been assessed in volume 2, chapter 9 of the Offshore EIA Report using the appropriate maximum design scenarios for these receptors. Reduction or disruption to prey availability through temporary and long-term subtidal habitat loss/disturbance, increased SSC and deposition, electromagnetic fields (EMF) from subsea electrical cabling, and colonisation of subsea structures, could affect kittiwake survival and productivity in the St. Abb’s Head to Fast Castle SPA kittiwake population.
  2. During the operation and maintenance phase, there is potential for temporary habitat loss/disturbance for up to 989,000 m2 as a result of the use of jack-up vessels during any component replacement activities and during any cable repair activities. These impacts will be similar to those identified for temporary habitat loss/disturbance during the construction phase (as discussed in the section on Project Alone: Construction and Decommissioning – Changes to prey availability for this SPA population) and will be highly restricted to the immediate vicinity of these operations.
  3. As outlined in the section on Project Alone: Construction and Decommissioning – Changes to prey availability above, the presence of infrastructure within the Proposed Development, will result in long-term habitat loss of up to 7,798,856 m2 during the operation and maintenance phase. These areas of habitat loss will be discrete, either in the immediate vicinity of foundations, or relatively small, isolated, stretches of cable, representing a very low proportion of available habitat (0.7% of the Proposed Development fish and shellfish ecology study area).
  4. Increased SSC could occur as a result of repair or remedial burial activities during the operation and maintenance phase. The maximum design scenario assessed in volume 2, chapter 9 of the Offshore EIA Report for increased SSC and associated deposition is for the repair of cables of up to 30,000 m in length and reburial of cables of up to 10,000 m in length for inter-array cables; and repair of cables of up to 4,000 m in length and reburial of cables of up to 4,000 m in length for offshore export cables, using similar methods as those for cable installation activities, e.g. jet-trenching, undertaken at intervals over the 35 years operation and maintenance phase. The assessment in volume 2, chapter 9 of the Offshore EIA Report considered that any suspended sediments and associated deposition will be of the same magnitude, or lower as for construction.
  5. The presence and operation of inter-array, interconnector and offshore export cables will result in emissions of localised EMF, which could potentially affect the sensory mechanisms of some species of fish. However, there is no evidence to suggest that the key prey species of kittiwake (e.g. sandeel, sprat and juvenile herring) are electrosensitive and would respond to electrical and/or magnetic fields (volume 2, chapter 9 of the Offshore EIA Report).
  6. Up to 10,198,971 m2 of habitat may be created due to the installation of jacket foundations and associated scour and cable protection measures. Artificial structures introduced to the marine environment provide hard substrate for settlement of various organisms, which can increase local food availability for higher trophic levels. Whilst there is mounting evidence of potential benefits of artificial structures in marine environment (Birchenough and Degrae 2020), the statistical significance of such benefits and details about trophic interactions, particularly in relation to key prey species for kittiwake, remain largely unknown (Peschko et al., 2020; BOWL 2021a, 2021b; Scott, 2022). Overall, any change in prey abundance and/or distribution through the presence of subsea structures of foundations is likely to be very small relative to the area over which breeding and non-breeding SPA kittiwakes forage.
  7. It is therefore considered that there is relatively little potential for the St Abb’s Head to Fast Castle 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 St. Abb’s to Fast Castle SPA kittiwake population. This conclusion is consistent with the outcome of the EIA which concluded that effects from changes in prey availability on kittiwakes during operation and maintenance were not significant in EIA terms (volume 2, chapter 11 of the Offshore EIA Report).
Project alone: population-level impacts
  1. As determined above, the effects from the Proposed Development alone which could lead to an adverse effect on the St Abb’s Head to Fast Castle SPA 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 5.20 and 5.21 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 in volume 3, appendix 11.6 of the Offshore EIA Report). The starting population size was the 2016 – 2020 count for the SPA, with the projected population trends considered over a 35 year timescale (volume 3, appendix 11.5 of the Offshore EIA Report). The PVAs used a matched runs approach to compare the un-impacted (i.e. baseline) and impacted populations (such that the stochasticity in the demographic rates was applied to each simulation prior to applying the impacts) and productivity was assumed to be unaffected by the displacement and collision effects on the adult and immature age classes. The PVA modelling was undertaken using the bespoke R-code for the Natural England nepva tools (Searle et al. 2019, Mobbs et al. 2020), with the code modified to allow a ‘burn-in’ period for establishing an initial population age structure (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 5.22:
Projected 35 Year Population Sizes and Associated PVA Metrics for the St Abb’s Head to Fast Castle SPA Kittiwake Population Under Different Impact Scenarios for the Proposed Development Alone

Table 5.22: Projected 35 Year Population Sizes and Associated PVA Metrics for the St Abb’s Head to Fast Castle SPA Kittiwake Population Under Different Impact Scenarios for the Proposed Development Alone

 

  1. The PVA predicted a continuing population decline for the St Abb’s Head to Fast Castle SPA kittiwake population, irrespective of the effects from the Proposed Development. Thus, under baseline conditions (i.e. no wind farm effects), the population is predicted to decline by 76% after 35 years from the current estimate of 10,904 adult birds (Table 5.22). Given that the PVAs are based on density independent models, which assume all mortality from the wind farm effects is additive and that there are no compensatory mechanisms operating within the population, the predicted declines are inevitably greater for those scenarios incorporating the effects from the Proposed Development.
  2. Considering the PVA metrics, the CPS values indicate that the SPA population size would be reduced by approximately 50% and 56 – 63%, relative to the predicted population size under baseline conditions, after 35 years for the Developer Approach and Scoping Approach, respectively (Table 5.22). Reductions in the annual population growth rate (relative to that predicted under baseline conditions) are estimated to be almost 2% on the basis of the Developer Approach and approximately 2.5% on the basis of the Scoping Approach (Table 5.22). On the basis of the Developer Approach, the centile value is estimated to be less than 10 after 35 years, whilst for the Scoping Approach the equivalent values are less than five (Table 5.22). Thus, the centile metric indicates little overlap in the distribution of the predicted impacted and un-impacted population sizes, suggesting a high likelihood of the impacted population being smaller than the un-impacted population after 35 years, irrespective of whether the effects are estimated using the Developer or Scoping Approaches.
  3. Whilst the PVA metrics indicate that the potential effects from the Proposed Development may be substantive at the population level, it is important to consider that the SPA population is predicted to decline irrespective of these effects and that such a trend is broadly consistent with the documented long-term trend for this population, albeit that there are indications of a levelling off in this decline over the past decade (Figure 5.13). Therefore, it seems likely that the SPA population will continue to remain well below the citation size and that the Proposed Development is unlikely to be the critical factor determining this, or indeed the overall population trend and condition status of the feature.
  4. The primary reasons for population decline in kittiwakes in the North Sea and the Forth and Tay region (including the St Abb’s Head to Fast Castle SPA) are likely to be fisheries management and climate change (Frederiksen et al., 2004). With fisheries now more appropriately managed in the Forth and Tay region (a sandeel fishery ban has been in place since 2000), it is possible that the recent stability in the numbers of breeding kittiwake at the St Abb’s Head to Fast Castle SPA may be sustained. However, changes caused by climate change, that are also likely to be affecting the SPA kittiwake population, may still be affecting the population in 35 years. The primary management option to prevent such climate change effects on kittiwake populations will be through global initiatives to mitigate greenhouse gas emissions (e.g. 21st Conference of the Parties of the UNFCCC (COP21)). Therefore, while the conservation status of the SPA population is projected to be in unfavourable condition, the effects of the Proposed Development, may not result in any important change to this, nor prevent recovery in the event of the factors causing population decline being reversed.
  5. Interpretation of the PVA metrics, and the implications for effects on the SPA population, should also be considered in the context of the high levels of precaution incorporated in the assessment. Differences between the Developer and Scoping Approaches in this respect have been discussed above (as well as in volume 3, appendices 11.3 and 11.4 of the Offshore EIA Report) but other likely sources of over-precaution in the assessment of the effects of the Proposed Development on this SPA population include:
  • Reliance on the seasonal mean peak abundance estimates within the Proposed Development array area and two kilometre buffer in determining displacement effects (with these estimates substantially higher than the seasonal means);
  • The assumption that displacement extends out to two kilometres from the Proposed Development Array and occurs at the same rate as within the Array, despite the lack of evidence for displacement of kittiwakes by offshore wind farms (Dierschke et al. 2016); and
  • Determining breeding season age classes on the basis of plumage characteristics of birds recorded during the baseline surveys, which overestimates the proportion of adults in the population (and hence also the impacts at the population level) because kittiwake may adopt adult plumage from their second year onwards (and certainly by their third year) although they do not start breeding until four years, on average (Coulson 2011).
    1. Perhaps most notably, the PVAs are based upon a density independent population model which is biologically implausible because it assumes no population regulation and permits unrealistic predictions of unlimited population growth. Instead, it is likely that compensatory density dependence will operate within the SPA population, so that mortality from the wind farm effects is offset to (at least) some degree by changes in other demographic parameters (e.g. increased rates of breeding productivity or reduced age of first breeding), as opposed to being wholly additive. There is empirical evidence for compensatory density dependence acting on seabird populations generally (Horswill et al. 2016), whilst for kittiwakes specifically, evidence supports the occurrence of intra-specific density dependent competition and the operation of compensatory density dependence (based on studies demonstrating, for example, that the numbers breeding at a colony are influenced by those at neighbouring colonies, that birds from larger colonies travel further to forage and that annual rates of increase in colony size are inversely related to the colony size whilst declines at colonies in northern parts of the UK have been greatest at the largest colonies - Furness and Birkhead 1984, Coulson 2011, Furness 2015, Wakefield et al. 2017). Although seabird populations may also be subject to depensatory density dependent effects (whereby the rate of decline increases as colony size reduces – e.g. due to increased vulnerability to predation), this is more likely to occur when populations are small and heading towards local extinction (Horswill et al. 2016). Therefore, the underlying basis for predicting the population-level impacts is unrealistic and likely to give overly precautionary outputs.