11.10. Measures Adopted as part of the Proposed Development

70. As part of the project design process, a number of measures have been proposed to reduce the potential for impacts on offshore and intertidal ornithology (see Table 11.18   Open ▸ ). As there is a commitment to implementing these measures, they are considered inherently part of the design of the Proposed Development and have therefore been considered in the assessment presented in section 11.11 below (i.e. the determination of magnitude and therefore significance assumes implementation of these measures). These measures are considered standard industry practice for this type of development.

Table 11.18: Designed In Measures Adopted as Part of the Proposed Development

11.11. Assessment of Significance

71. The potential impacts arising from the construction, operation and maintenance and decommissioning phases of the Proposed Development are listed in Table 11.13   Open ▸ , along with the maximum design scenario against which each impact has been assessed.
72. An assessment of the likely significance of the effects of the Proposed Development on offshore and intertidal ornithology receptors caused by each identified impact is given below.

Disturbance and displacement from increased vessel activity and other construction activity within proposed development array area

73. Direct temporary disturbance or displacement of birds within the Proposed Development array area during the construction, operation and maintenance, and decommissioning phases will occur as a result of a range of activities including use of jack-up vessels during foundation installation/maintenance, installation and maintenance of inter-array and offshore export cables (including seabed clearance operations prior to cable installation) and anchor placements associated with these activities. Disturbance arising from these operations has the potential to affect identified key species directly (e.g. disturbance of individuals) and indirectly (e.g. disturbance to prey distribution or availability). The maximum design scenario, outlined in Table 11.13   Open ▸ , describes the elements of the Proposed Development considered within this assessment.

Construction Phase

Magnitude of Impact

74. Activities resulting in the disturbance or displacement of birds from increased vessel activity and construction activity will occur intermittently throughout the construction period. The offshore construction works which includes activities resulting in temporary disturbance or displacement of birds from increased vessel activity are assumed to be undertaken over a period of 4 years and 8 months between 2026 and 2032, which represents a reasonable worst case for the purposes of assessment.
75. The impact is predicted to be of local spatial extent, intermittent, medium-term duration (although only a small proportion of the total area will be affected at any one time, with individual elements of construction having much shorter durations) and will affect any birds in the vicinity of these activities directly. The magnitude is considered to be negligible.

Sensitivity of the Receptor

76. Some species are more susceptible to disturbance than others. There is evidence from studies that demonstrate that species such as divers and scoters may avoid shipping by several kilometres (e.g. Garthe and Hüppop, 2004; Schwemmer et al. 2011), while gulls are not considered susceptible to disturbance, as they are often associated with fishing boats (e.g. Camphuysen, 1995; Hüppop and Wurm, 2000). 
77. In order to focus the assessment, a screening exercise was undertaken to identify those species likely to be susceptible to disturbance and displacement as a result of increased vessel activity associated with construction ( Table 11.19   Open ▸ ). This was based on previous sensitivity reviews such as Garthe and Hüppop (2004), who developed a scoring system for such disturbance factors, which is used widely in offshore wind farm EIAs. Similarly, Furness and Wade (2012) developed disturbance ratings for particular species based on Garthe and Hüppop (2004), alongside scores for habitat flexibility and conservation importance in a Scottish context. These factors were used to define an index value that highlights the sensitivity of a species to disturbance and displacement. Any species with a low sensitivity to disturbance or displacement or that was recorded only in very small numbers within the Offshore Ornithology study area was screened out of further assessment.

Table 11.19: Sensitivity of Species to disturbance and displacement from increased vessel activity in Proposed Development Array Area during Construction Phase

78. Two species (guillemot and razorbill) were identified as being potentially sensitive to disturbance and displacement from increased vessel activity within the Proposed Development array area during the construction phase.
79. Previous reviews concluded that guillemots and razorbills have a medium sensitivity to disturbance and displacement, based on their sensitivity to ship and helicopter traffic in Garthe and Hüppop (2004), Furness and Wade (2012), Furness et al. (2013) and Bradbury et al. (2014). Therefore, there is potential for disturbance and displacement of guillemots and razorbills due to construction activity, including wind turbine construction and associated vessel traffic. On this basis, guillemot and razorbill have been screened in for further assessment ( Table 11.19   Open ▸ ). All other species have been screened out.
80. Construction will not occur across the whole of the Proposed Development array area at the same time, but will be completed via a series of construction campaigns,
81. Any impacts resulting from disturbance and displacement from construction activities are considered likely to be short-term, temporary and reversible in nature, lasting only for the duration of construction activity, with birds expected to return to the area once construction activities have ceased. Consequently, any disturbance effects will occur only in the areas where vessels are operating at any given point and not over the entire site. The magnitude of the impact is therefore deemed to be negligible.

Sensitivity of the Receptor

82. Based on previous reviews as detailed above, guillemot and razorbill sensitivity to displacement associated with vessel movements vessels during the construction phase is considered to be medium.

Significance of the Effect

83. For guillemot and razorbill, the magnitude of the impact is deemed to be negligible and the sensitivity of these two species is considered to be medium. The effect on these two species will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

84. No offshore and intertidal ornithology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 11.10) is not significant in EIA terms. Therefore, the residual impact is considered to be of negligible to minor adverse significance, which is not significant in EIA terms.

Operation and Maintenance Phase

Magnitude of Impact

85. During the operation and maintenance phase, disturbance or displacement of birds from increased vessel activity will be at a lower, more localised scale, restricted to around individual wind turbines where maintenance is being conducted.
86. The impact is predicted to be of local spatial extent, intermittent, short-term duration (individual maintenance operations will occur over a period of days to weeks) and will affect any birds in the vicinity of these activities directly. The magnitude is considered to be negligible.

Sensitivity of the Receptor

87. The sensitivity of offshore and intertidal birds to disturbance and displacement arising from increased vessel activity during the operation and maintenance phase can be found in the construction phase assessment above (paragraph 82 et seq.).

Significance of the Effect

88. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the majority of species is considered to be low (Table 11.20). The effect on these species will, therefore, be of negligible to minor significance, which is not significant in EIA terms.
89. For guillemot and razorbill, the magnitude of the impact is deemed to be negligible and the sensitivity of these two species is considered to be medium. The effect on these two species will, therefore, be of negligible to minor significance, which is not significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

90. No offshore and intertidal ornithology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 11.10) is not significant in EIA terms. Therefore, the residual impact is considered to be of negligible to minor adverse significance, which is not significant in EIA terms.

Decommissioning Phase

Magnitude of Impact

91. Activities resulting in the disturbance or displacement of offshore and intertidal birds from increased vessel activity will occur intermittently throughout the decommissioning period. The offshore decommissioning phase which includes activities resulting in temporary disturbance or displacement of birds from increased vessel activity is predicted to not exceed the construction period. Overall, the magnitude of impacts arising during the decommissioning phase are predicted to be the same as for the construction period.
92. The impact is predicted to be of local spatial extent, intermittent, medium-term duration (although only a small proportion of the total area will be affected at any one time, with individual elements of decommissioning having much shorter durations) and will affect any birds in the vicinity of these activities directly. The magnitude is considered to be negligible.

Sensitivity of the Receptor

93. The sensitivity of offshore and intertidal birds to disturbance and displacement arising from increased vessel activity and other construction activity during the decommissioning phase can be found in the construction phase assessment above (paragraph 82 et seq.).

Significance of the Effect

94. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the majority of species is considered to be low ( Table 11.19   Open ▸ ). The effect on these species will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.
95. For guillemot and razorbill, the magnitude of the impact is deemed to be negligible and the sensitivity of these two species is considered to be medium. The effect on these two species will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

96. No offshore and intertidal ornithology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 11.10) is not significant in EIA terms. Therefore, the residual impact is considered to be of negligible to minor adverse significance, which is not significant in EIA terms.

Disturbance from aviation and navigation lighting

97. There is the potential that aviation and navigation lighting on wind turbines could attract or repel birds moving through the Proposed Development at night. There is some evidence that nocturnal lighting may cause changes in bird behaviour and habitat selection (Drewitt and Langston, 2008). However much of this evidence is based on oil and gas platforms, and as offshore wind farms are typically less intensively lit than these installations, any impacts are likely to be less extreme. It is currently planned that only the peripheral wind turbines will be illuminated (with red aviation and yellow navigation lighting). All other wind turbines will be unlit apart from small white lamps above wind turbine access doors. Based on available evidence, it is considered that red lighting (i.e., aviation warning lights) may have minimal effects on seabirds, with yellow lighting (i.e., navigational lighting) also having low impacts (Syposz et al, 2021).
98. Any impacts are considered to be restricted to the operation and maintenance phase.

Operation and Maintenance Phase

Magnitude of Impact

99. A significant impact could potentially occur if large numbers of migrants fly through the Proposed Development in a single event, leading to mass disorientation or collisions. However, there is no evidence from any existing UK offshore wind farm to suggest mass collision events occur as a result of aviation and navigation lighting that is typically used for UK offshore wind farms. Evidence from Kerlinger et al., (2010) and Welcker et al., (2017) found that nocturnal migrants do not have a higher risk of collision with wind farms than species that migrate during daylight, while mortality rates are not higher at offshore wind farms with lighting compared to those without. Furthermore, studies have shown that nocturnal flight is altered to counteract the risk of collision at offshore wind farms (Dirksen et al., 1998 and Desholm and Kahlert, 2005). Based on these studies, it is considered that the potential magnitude of impacts would be no greater than negligible to birds with respect to lighting.

Sensitivity of the Receptor

100. The seabird species that are considered most at risk of collisions with wind turbines (gannet and kittiwake), are unlikely to be active at night, as they either return to their colonies or roost on the sea surface during darkness (Wade et al., 2016). A tracking study by Furness et al., (2018) reported that gannet flight and diving activity was minimal during the night. Kotzerka et al., (2010) reported that kittiwake foraging trips mainly occurred during daylight hours and that birds were largely inactive at night and therefore at lower risk of interactions with wind turbines.
101. Gulls are known to have low to moderate levels of nocturnal activity but are sometimes attracted to lit fishing vessels and well-lit oil and gas platforms that attract fish to the surface waters (Burke et al., 2012). However, it is considered that as offshore wind farms are typically considerably less intensively lit than these installations, the degree of nocturnal attraction for large gull species is likely to be lower.
102. Overall, it is considered likely that seabird species in the marine environment would exhibit no more than a medium sensitivity to lighting associated with the Proposed Development.

Significance of the Effect

103. Overall, the magnitude of the impact is deemed to be negligible, and the sensitivity of species is considered to be no more than medium (Table 11.20). The effect will therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

104. No offshore and intertidal ornithology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 11.10) is not significant in EIA terms. Therefore, the residual impact is considered to be of negligible to minor adverse significance, which is not significant in EIA terms.

Indirect effects as a result of habitat loss/displacement of prey species due to increased noise and disturbance to seabed

105. Indirect disturbance and displacement of birds may occur during the construction phase if there are impacts on prey species and/or the habitats of prey species. These indirect effects include those resulting from the production of underwater noise (e.g. during piling) and the generation of suspended sediments (e.g. during preparation of the seabed for wind turbine foundations). Such activities may change the behaviour or availability of prey species for seabirds. Underwater noise may cause fish and mobile invertebrates to avoid the area of construction and may also affect their physiology and behaviour. Suspended sediments may cause fish and mobile invertebrates to avoid the construction area and may smother and hide immobile benthic prey. These outcomes may lead to a reduction in prey being available within the construction area for foraging seabirds. Such potential effects on benthic invertebrates and fish have been assessed in volume 2, chapter 7, chapter 8 and chapter 9. The conclusions of those assessments inform this assessment of indirect effects on ornithological receptors.

Construction Phase

Magnitude of Impact

106. For seabirds, the key prey species are likely to be herring, sprat and sandeel. Based on information presented in volume 2, chapter 9, adult fish species are more mobile than juveniles, and may show avoidance behaviour within areas affected by increased suspended sediments concentrations (SSC), making them less susceptible to physiological effects of this impact. Juvenile fish are therefore more likely to be affected by such habitat disturbances, as they are typically less mobile and so less able to avoid such impacts. However, natural temporary increases in SSC associated with winter storm events are also likely to occur in the area, therefore it is expected that most juvenile fish likely to occur in the vicinity of construction activities 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 for these species and will reduce to background concentrations within a very short period (approximately two tidal cycles).
107. Volume 2, chapter 7 outlines physical changes to the seabed and to suspended sediment levels, and discusses the nature of any change and impact. Such changes are considered to be temporary, small scale and highly localised, and therefore any associated effects are concluded to be of negligible to minor significance (see volume 2, chapter 7).
108. Temporary habitat loss/disturbance of benthic habitats within the Proposed Development will occur during the construction, operation and maintenance, and decommissioning phases. Temporary habitat loss/disturbance can result from activities including use of jack-up vessels during foundation installation, sandwave and boulder clearance, cable installation and repair as well as anchor placements associated with these activities. Installation of the Proposed Development infrastructure, resulting in the temporary subtidal habitat loss/disturbance will occur intermittently throughout the construction period.
109. For subtidal benthic habitats, the magnitude of the impact is deemed to be medium, and the sensitivity of the receptor is considered to be medium. Although this effect will, therefore, be of moderate adverse significance in the short term (i.e. within two years of completion of construction activities) (see volume 2, chapter 8), it is not predicted to have a significant impact on prey fish species in the vicinity (see volume 2, chapter 9), therefore there is not considered to be any corresponding indirect effect on seabirds foraging in the vicinity.
110. For most marine and diadromous fish species, the magnitude of the impact is low, and the sensitivity is considered to be low, therefore the effect will be of minor adverse significance, which is not significant in EIA terms. For sandeels, the magnitude of the impact is low and the sensitivity is considered to be medium. The effect will, therefore, be of minor significance which is not significant in EIA terms (see volume 2, chapter 9).
111. In addition to potential impacts on fish species distribution arising from increases in SSC affecting foraging seabirds, there is also the potential for increased SSC affecting the ability of foraging seabirds to detect prey. However, as for the fish species present in the area, natural temporary increases in SSC associated with winter storm events are also likely to occur, therefore it is expected that most foraging seabirds likely to occur in the vicinity of construction activities 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 for these species and will reduce to background concentrations within a very short period (approximately two tidal cycles). Known foraging ranges of seabirds are considerably larger than the temporary, localised effects from increases in SSC as a result of construction activities, therefore significant impacts on foraging seabirds in the vicinity of these construction activities are not considered likely to occur.
112. Overall, impacts from increased suspended sediments during the construction phase are considered to be of minor adverse significance for marine fish species and of negligible to minor adverse significance for diadromous fish species, which is not significant in EIA terms (see volume 2, chapter 7).
113. Noise impacts on marine and diadromous fish were predicted to arise from from activities such as pile driving for jacket foundations and UXO clearance. Underwater noise can potentially have an adverse impact on fish species ranging from physical injury/mortality to behavioural effects. Injury and/or mortality for all fish and shellfish species is to be expected for individuals within very close proximity to piling operations, however, “soft start” procedures will allow mobile individuals in close proximity to flee the area prior to maximum hammer energy levels. Overall, noise impacts were considered to be of minor adverse significance for marine and diadromous fish species, which is not significant in EIA terms (see volume 2, chapter 9).
114. Following a negligible or minor adverse impact on fish that are prey species for seabirds, the impact on seabirds is predicted to be of local spatial extent, medium term duration and intermittent, (although only a small proportion of the total area will be affected at any one time, with individual elements of construction having much shorter durations). It is predicted that the impact will affect seabirds indirectly. The magnitude is therefore considered to be negligible.

Sensitivity of the Receptor

115. As already outlined, construction activities may change the behaviour or availability of prey species for seabirds, resulting in the availability of such prey species being temporarily reduced. However, the majority of seabird species have a variety of target prey species and have large foraging ranges, meaning that they can forage for alternative prey species or move to other foraging areas if prey becomes temporarily unavailable due to construction activities. 
116. The sensitivity of seabirds to indirect effects as a result of habitat loss or displacement of prey species due to increased noise and disturbance during construction is therefore considered to be low.

Significance of the Effect

117. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of seabirds to this impact is considered to be low. The effect on these species will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

118. No offshore and intertidal ornithology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 11.10) is not significant in EIA terms. Therefore, the residual impact is considered to be of negligible to minor adverse significance, which is not significant in EIA terms.

Operation and Maintenance Phase

Magnitude of Impact

119. Long term subtidal habitat loss impacts will occur during the construction phase and will be continuous throughout the anticipated 35 year operation and maintenance phase. Long term habitat loss will occur directly under all wind turbine and OSP foundation structures (suction caisson and piled jacket foundations respectively), associated scour protection and cable protection (including at cable crossings) where this is required. The seabed habitats removed by the installation of infrastructure will reduce the amount of suitable habitat and available food resource for fish and shellfish species and communities associated with the baseline substrates/sediments, which could in turn, reduce the availability of these prey fish species for foraging seabirds in the vicinity.
120. However, the majority of fish species would be able to avoid habitat loss effects due to their greater mobility and would recover into the areas affected following cessation of construction. Sandeels (and other less mobile prey species) would be affected by long term subtidal habitat loss, although recovery of this species is expected to occur quickly as the sediments recover following installation of infrastructure and adults recolonise and also via larval recolonisation of the sandy sediments which dominate the Proposed Development fish and shellfish ecology study area.
121. Overall, the effect on fish species is considered to be of minor adverse significance, which is not significant in EIA terms (see volume 2, chapter 9).  
122. Following a minor adverse impact on fish that are prey species for seabirds, the impact on seabirds is predicted to be of local spatial extent, indirect and of medium-term duration, as prey species distribution is considered likely to recover over time. The magnitude is therefore considered to be negligible.

Sensitivity of the Receptor

123.  The sensitivity of the offshore and intertidal birds to indirect effects as a result of habitat loss or displacement of prey species due to increased noise and disturbance during construction during the decommissioning phase can be found in the construction phase assessment above (paragraph 115 et seq.).

Significance of the Effect

124. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of offshore and intertidal birds to this effect is considered to be low. The effect on these species will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

125.  No offshore and intertidal ornithology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 11.10) is not significant in EIA terms. Therefore, the residual impact is considered to be of negligible to minor adverse significance, which is not significant in EIA terms.

Decommissioning Phase

Magnitude of Impact

126. Activities resulting in indirect effects on offshore and intertidal birds as a result of habitat loss or displacement of prey species due to increased noise and disturbance during decommissioning will occur intermittently throughout the decommissioning period. The offshore decommissioning phase which includes activities resulting in temporary disturbance or displacement of birds from increased vessel activity is predicted to not exceed the construction period.
127. The impact is predicted to be of local spatial extent, intermittent, medium-term duration (although only a small proportion of the total area will be affected at any one time, with individual elements of decommissioning having much shorter durations) and will affect any birds in the vicinity of these activities directly. The magnitude is considered to be negligible.

Sensitivity of the Receptor

128. The sensitivity of the offshore and intertidal birds to indirect effects as a result of habitat loss or displacement of prey species due to increased noise and disturbance during construction during the decommissioning phase can be found in the construction phase assessment above (paragraph 115 et seq.).

Significance of the effect

129. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of offshore and intertidal birds to this effect is considered to be low. The effect on these species will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

130. No offshore and intertidal ornithology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 11.10) is not significant in EIA terms. Therefore, the residual impact is considered to be of negligible to minor adverse significance, which is not significant in EIA terms.

Disturbance and loss of seabed habitat arising from cable installation/removal within the Outer Firth of Forth and St Andrews Bay Complex SPA

131. Direct temporary disturbance or displacement of birds along the offshore export cable corridor within the Outer Firth of Forth and St Andrews Bay Complex SPA may occur during the construction, operation and decommissioning phases, as a result of installation, maintenance and removal of the offshore export cables (including seabed clearance operations prior to cable installation) and anchor placements associated with these activities. Disturbance arising from these activities has the potential to affect identified species directly (e.g. disturbance of individuals) and indirectly (e.g. disturbance to prey distribution or availability). The maximum design scenario, outlined in Table 11.13   Open ▸ , describes the elements of the proposed project considered within this assessment.

Construction Phase

Magnitude of Impact

132. Activities resulting in the disturbance or displacement of birds within the Outer Firth of Forth and St Andrews Bay Complex SPA as a result of increased vessel activity along the Proposed Development export cable corridor may occur intermittently throughout the construction period. Installation and maintenance of offshore export cables (including seabed clearance operations prior to cable installation) will occur over a period of up to 24 months.
133. Up to eight export cables will be trenched and buried, each a maximum of 109 km long, however this includes lengths of export cable within the array area, outside of the SPA boundary. It is estimated that total impacts from trenching and burying the cable will impact a 15 m wide corridor of seabed and therefore a total of 12.43 km2 of seabed could be disturbed during the trenching and burying of the export cables. It is estimated that approximately 15% of the cable route may need protection, which would be a permanent loss of seabed. If this is the case, then an estimated 2.616km2 of seabed could be lost due to cable protection.
134. Cables will be trenched and buried using either mechanical ploughs or cutters or by high pressure jets depending on the ground conditions. If cable protection is not required, the trenches will backfill naturally over time. The length of time it takes for the trenches to backfill will be dependent on the local seabed conditions and currents.
135. In areas of soft mud or sand, natural infill is predicted to occur rapidly and studies have indicated that infill of trenches can occur at a rate of between 0.2 and 0.5 m every six months, with sediment communities returning to the area of disturbed sediment within 12 months of the cable laying having been undertaken (BERR, 2008). Consequently, the potential impacts from trenching cables within the SPA will be localised and temporary and will not have a long-term impact on the habitat.
136. It is concluded that the very small area of seabed habitat lost within the SPA as a result of cable protection will not cause a significant reduction in the extent, distribution or quality of habitats that support the qualifying species or their prey. The trenching of cables will cause a localised and temporary impact on the habitats within the SPA.
137. Direct disturbance impacts are predicted to be of local spatial extent, intermittent, medium-term duration (although only a small proportion of the total area will be affected at any one time, with individual elements of decommissioning having much shorter durations) and will only affect any birds in the vicinity of these activities directly. Overall, the magnitude of these impacts is considered to be negligible.

Sensitivity of the Receptor

138. Some seabird species are more susceptible to disturbance than others. There is evidence from studies that demonstrate that species such as divers and scoters may avoid shipping by several kilometres (e.g. Garthe and Hüppop, 2004; Schwemmer et al. 2011), while gulls are not considered susceptible to disturbance, as they are often associated with fishing boats (e.g. Camphuysen, 1995; Hüppop and Wurm, 2000). 
139. In order to focus the assessment, a screening exercise was undertaken to identify those species of qualifying interest for the Outer Firth of Forth and St Andrews Bay Complex SPA that are likely to be susceptible to disturbance and displacement from installation of the offshore export cables ( Table 11.20   Open ▸ ). This was based on previous sensitivity reviews such as Garthe and Hüppop (2004), who developed a scoring system for such disturbance factors, which is used widely in offshore wind farm EIAs. Similarly, Furness and Wade (2012) developed disturbance ratings for particular species based on Garthe and Hüppop (2004), alongside scores for habitat flexibility and conservation importance in a Scottish context. These factors were used to define an index value that highlights the sensitivity of a species to disturbance and displacement. In addition, rankings from two similar reviews (Furness et al., 2013 and Bradbury et al., 2014) were also compared and used to inform this screening exercise.
140. Any species with a moderate or high sensitivity to disturbance or displacement that is listed as a Qualifying Interest for the Outer Firth of Forth and St Andrews Bay Complex SPA was screened into the assessment.

Table 11.20: Sensitivity to Disturbance and Displacement from Increased Vessel Activity for Species Listed as Qualifying Interests for the Outer Firth of Forth and St Andrews Bay Complex SPA

141. A total of four species that are listed as Qualifying Interests for the Outer Firth of Forth and St Andrews Bay Complex SPA (eider, common scoter, goldeneye and red-throated diver), were screened in for further assessment, on the basis that they were of high sensitivity to disturbance and displacement from increased vessel activity associated with construction activities, based on sensitivity rankings in Garthe and Hüppop (2004), Furness and Wade (2012), Furness et al., (2013) and Bradbury et al., (2014) ( Table 11.20   Open ▸ ).
142. In addition, six species (red-breasted merganser, shag, velvet scoter, Slavonian grebe, guillemot and razorbill) were screened in for further assessment on the basis that they were of moderate sensitivity to disturbance and displacement from increased vessel activity associated with construction activities, based on sensitivity rankings in Garthe and Hüppop (2004), Furness and Wade (2012), Furness et al., (2013) and Bradbury et al., (2014) ( Table 11.20   Open ▸ ).
143. Of these six species, velvet scoter and Slavonian grebe were not recorded on digital aerial surveys within the Offshore Ornithology study area, or on surveys undertaken in the Intertidal Ornithology study area. The four remaining species (eider, common scoter, red-breasted merganser and goldeneye were recorded on nearshore surveys undertaken as part of baseline surveys for the intertidal export cable landfall sites. Eider was the most abundant and regularly present waterfowl species on these surveys, and birds were recorded on every month of the survey programme, with numbers typically ranging between one to 30 individuals. All birds were recorded within 1 km of the shore. Common scoters were recorded infrequently on nearshore surveys, with typically counts of fewer than 30 individuals recorded. All birds were recorded between 500 m and 1 km from shore. Red-breasted mergansers were recorded intermittently on nearshore surveys, predominantly during the winter and passage months in low numbers of no more than five birds. Almost all birds were recorded within 500 m of the shore. Goldeneye were recorded intermittently, predominantly during the winter and passage months in low numbers of no more than seven birds. Almost all birds were recorded within 500 m of the shore. All remaining wildfowl and wader species recorded during the inter-tidal surveys were not listed as qualifying species for the Outer Firth of Forth and St Andrews Bay Complex SPA, and numbers recorded on surveys did not exceed the 1% threshold of national importance (volume 3, appendix 11.2).
144. The Outer Firth of Forth and St Andrews Bay Complex SPA, supports the largest aggregations of eider in Scotland. Eider are resident throughout the year, with an inshore, coastal distribution. Common scoter occur in large numbers in the non-breeding season, with the majority of birds being found in inshore, coastal waters, particularly in St Andrews Bay and in the Firth of Forth. Goldeneye occur in peak numbers in the non-breeding season, primarily within the Firth of Forth, while peak numbers of red-breasted mergansers also occur in the non-breeding season, in the inshore, coastal waters of St Andrews Bay and the Firth of Forth (NatureScot, 2016).
145. Therefore, there is potential for disturbance and displacement of these ten species due to export cable construction activity within the Outer Firth of Forth and St Andrews Bay Complex SPA. However, construction will not occur within the whole of the Proposed Development export cable corridor at the same time, but will be carried out sequentially, as the cable-laying vessels move along the route. Consequently, any effects will only occur in the immediate vicinity where vessels are operating at any given point and not over the entire route. As a result, any effects will be very localised, temporary and short-term in duration, affecting only a very small extent of the areas used by these species. On this basis, any disturbance or displacement impact is considered to be negligible.

Significance of the Effect

146. Overall, for red-breasted merganser, shag, velvet scoter, Slavonian grebe, guillemot and razorbill, the magnitude of the impact is deemed to be negligible and the sensitivity is considered to be medium. The effect on these species will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.
147. For eider, common scoter, goldeneye and red-throated diver, the magnitude of the impact is deemed to be negligible and the sensitivity of these species is considered to be high. The effect on these species will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

148. No offshore and intertidal ornithology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 11.10) is not significant in EIA terms. Therefore, the residual impact is considered to be of minor adverse significance, which is not significant in EIA terms.

Operation and Maintenance Phase

Magnitude of Impact

149. Activities resulting in the disturbance or displacement of birds within the Outer Firth of Forth and St Andrews Bay Complex SPA as a result of increased vessel activity along the Proposed Development export cable corridor may occur occasionally throughout the operation period. Maintenance and potentially replacement of offshore export cables may be required throughout the operation period.
150. Predicted worst case is four export cable reburial events and four export cable repair events of up to 1,000m each over project lifetime. Routine annual cable inspections will also be conducted.
151. It is concluded that the very small area of seabed habitat disturbance within the SPA as a result of cable reburial/replacement will not cause a significant reduction in the extent, distribution or quality of habitats that support the qualifying species or their prey. The re-burial of cables (if required) will cause a localised and temporary impact on the habitats within the SPA.
152. Direct disturbance impacts are predicted to be of local spatial extent, occasional, short-term duration (although only a small proportion of the total area will be affected at any one time), in the vicinity of the maintenance activities, which will only affect birds in the vicinity of these activities directly. Overall, the magnitude of these impacts is considered to be negligible.

Sensitivity of the Receptor

153. The sensitivity of the species that are listed as Qualifying Interests for the Outer Firth of Forth and St Andrews Bay Complex SPA to disturbance and displacement arising from increased vessel activity within the Proposed Development export cable corridor during the decommissioning phase can be found in the construction phase assessment above (paragraph 138 et seq.).

Significance of the Effect

154. Overall, for red-breasted merganser, shag, velvet scoter, Slavonian grebe, guillemot and razorbill, the magnitude of the impact is deemed to be negligible and the sensitivity is considered to be medium. The effect on these species will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.
155. For eider, common scoter, goldeneye and red-throated diver, the magnitude of the impact is deemed to be negligible and the sensitivity of these species is considered to be high. The effect on these species will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

156. No offshore and intertidal ornithology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 11.10) is not significant in EIA terms. Therefore, the residual impact is considered to be of minor adverse significance at worst, which is not significant in EIA terms.

Decommissioning Phase

Magnitude of Impact

157. Activities resulting in the disturbance or displacement of species that are listed as Qualifying Interests for the Outer Firth of Forth and St Andrews Bay Complex SPA from increased vessel activity within the Proposed Development export cable corridor will occur intermittently throughout the decommissioning period. The offshore decommissioning phase which includes activities resulting in temporary disturbance or displacement of birds from increased vessel activity is predicted to not exceed the construction period.
158. The impact is predicted to be of local spatial extent, intermittent, medium-term duration (although only a small proportion of the total area will be affected at any one time, with individual elements of decommissioning having much shorter durations) and will affect any birds in the vicinity of these activities directly. The magnitude is therefore considered to be negligible.

Sensitivity of the Receptor

159. The sensitivity of the species that are listed as Qualifying Interests for the Outer Firth of Forth and St Andrews Bay Complex SPA to disturbance and displacement arising from increased vessel activity within the Proposed Development export cable corridor during the decommissioning phase can be found in the construction phase assessment above (paragraph 138 et seq.).

Significance of the Effect

160. Overall, for red-breasted merganser, shag, guillemot and razorbill, the magnitude of the impact is deemed to be negligible and the sensitivity is considered to be medium. The effect on these species will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.
161. For eider, common scoter, goldeneye and red-throated diver, the magnitude of the impact is deemed to be negligible and the sensitivity of these species is considered to be high. The effect on these species will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

162. No offshore and intertidal ornithology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 11.10) is not significant in EIA terms. Therefore, the residual impact is considered to be of no more than minor adverse significance, which is not significant in EIA terms.

Displacement and barrier effects from offshore infrastructure

163. Displacement and/or barrier effects on birds within the Proposed Development and immediate surrounding area during the operation phase may occur as a result of the presence of the operational wind turbines. Displacement and barrier effects have been considered together following the approach presented in SNCB guidance (2017).
164. Displacement and/or barrier effects resulting from the presence of offshore wind turbines has the potential to affect individuals of sensitive bird species directly. In effect, this represents indirect habitat loss, which would potentially reduce the area available to forage, rest and/or moult for sensitive seabirds that currently occur within and around the Proposed Development. Displacement may contribute to the overall fitness of individual birds, which could also affect individual breeding success or at an extreme level, could cause mortality of individuals.
165. The maximum design scenario, outlined in Table 11.13   Open ▸ , describes the elements of the proposed project considered within this assessment.

Approach

166. SNCB guidance considers that displacement effects have to be assessed for the proposed development site as well as a surrounding 2 km buffer around the site (SCNBs, 2017). The method to calculate the mean seasonal peak (MSP) population estimates for relevant species for the Proposed Development array area and 2 km buffer was as follows:

• MSP population estimates were calculated for each species in each appropriate bio-season, taken as an average over the two years of surveying (March 2019 – March 2021). For example, the MSP population estimate for the breeding season was calculated as the average of the peak count in the breeding season in year one and the peak count in the breeding season in year two.

• For seasons starting or ending halfway through the month, the 15th/16th was used as a mid-month cut off. Surveys were assigned to a breeding season based on the date that the survey was flown, with some exceptions to ensure even coverage of months in both years.
  167. Further details are presented in section 3.2 of volume 3, appendix 11.1. Seasonal mean peak abundances for the Proposed Development array area plus 2 km buffer are presented below for the relevant key species.

PVA Approach

168. Population Viability Analysis (PVA) of predicted displacement mortality was conducted for breeding colonies for the five key displacement species within multiple SPAs. The species/ SPA combinations modelled were chosen using a threshold approach advised in the Scoping Opinion (MS-LOT, 2022) and confirmed through the Ornithology Roadmap process (Meeting 6, 10th May 2022). Further details of the SPA combinations and impact scenarios used are presented in volume 3, appendix 11.6.
169. For each of these SPAs, the specific mortality scenarios used within each of the individual species PVAs were assumed. For this assessment, regional estimates are in essence a sum of projected population sizes, at each timepoint, for each of the constituent SPAs for the five key displacement species.
170. In detail 5,000 simulated population projections were run for each species, SPA and impact scenario. These were summed over SPAs for each projection year, within each species and impact scenario. This provided 5,000 regional population simulations for each species and impact scenario. The summary statistics and counterfactuals were calculated subsequently. Results for the 35-year period are presented and discussed for each of the key displacement species below. Results for the 50-year period are presented in volume3, appendix 11.6 for context.
171. It should be noted that for four of the key seabird species considered here, the regional populations as defined in the breeding and non-breeding seasons in this chapter are different (i.e., they derive from a very different composition of source populations/colonies). The PVAs are relevant to the regional population as defined for the breeding season but not to that defined for the non-breeding season (with the exception of guillemot). The PVAs also account for effects on this regional breeding population during both breeding and non-breeding periods. However, overall, the results of the regional PVAs are considered indicative for assessment purposes.

Reference Populations

172. For each of the five key species assessed for displacement impacts during the operation phase, reference populations were required for comparison with the number of birds considered likely to suffer mortality. For the breeding season assessment, the total number of breeding adults from all colonies within mean maximum foraging range + 1 S.D. were used, as estimated by Woodward et al., (2019), ( Table 11.9   Open ▸ ) (volume 3, appendix 11.5).
173. Corresponding reference populations for the BDMPS bio-seasons that make up the non-breeding season were taken from Furness (2015) ( Table 11.9   Open ▸ ).
174. The overall baseline mortality rates presented for each species were derived from the relevant annual mortality rate calculation for each age class (where available) from the PVA work, as presented in Table 11.21   Open ▸ . Further details are provided in volume 3, appendix 11.6. The potential magnitude of impact was estimated by calculating the increase in either the adult baseline mortality (for the breeding season) or the average baseline mortality across all age classes for the other bio-seasons with respect to the regional populations.

Table 11.21: Average Mortality Rates Across All Age Classes of Key Species Considered for Displacement Assessment and Collision Assessment

1 Demographic rate and population age ratio were based on data from Forth Islands SPA. See volume 3, appendix 11.6.

Operation and Maintenance Phase

175. Consultation representations and advice from MSS and NatureScot (4 February 2022) and discussions through the Ornithology Road Map process (volume 3, appendix 11.8), led to agreement that a displacement assessment was required for five species:

• gannet;
• kittiwake;
• guillemot;
• razorbill; and
• puffin.
  176. These five species were selected based on their abundance in the Proposed Development, highlighted by the two years of baseline data (volume 3, appendix 11.1), and on evidence about their sensitivity to displacement and barrier effects (Furness et al., 2013; Bradbury et al., 2014; SNCBs, 2017).
  177. For the displacement assessment for the operation phase, two approaches were undertaken – the Developer Approach and the Scoping Approach. While the Developer Approach is largely in accordance with the Scoping Opinion, there are differences between the two approaches, and justification for these differences are presented in volume 3, appendix 11.4.
  178. The Scoping Opinion contained advice on the displacement and mortality rates to be used for the SNCB Matrix Approach. In addition, the Scoping Opinion (and subsequent advice received during the Ornithology Roadmap Process (volume 3, appendix 11.8) also recommended that estimates of displacement and barrier effects as generated by the publicly available individual-based modelling approach “SeabORD” (Searle et al. 2018), should be presented for kittiwake, guillemot, razorbill and puffin, if feasible. 
  179. In addition, since SeabORD does not include gannet, MSS, in their scoping representation of 16th December 2021, advised that an analysis of the extensive gannet GPS tracking data from the Bass Rock colony be undertaken to inform assessment of displacement and barrier effects for this species. Details of the analysis undertaken are given in volume 3, appendix 11.4, annex E, following the approach agreed through the Ornithology Roadmap Process (volume 3, appendix 11.8). 
  180. As part of the Developer Approach, a review of recent displacement rates applied by other assessments of displacement for offshore wind farms was undertaken for each of the five key species. A further review of the displacement values derived from multiple post-consent monitoring reports was undertaken to quantify a suitable evidence-led approach and to provide transparency on how the displacement rates used in the Developer Approach assessment were calculated (see volume 3, appendix 11.4).
  181. The displacement assessments for the five key species are presented below. A summary of the displacement and mortality rates used in both the Scoping Approach and the Developer Approach is provided in Table 11.22   Open ▸ .

Table 11.22: Displacement and Mortality Rates used for the Scoping Approach (Scoping Opinion 4 February 2022) and the Developer Approach

1 Recommended maximum displacement rate from APEM (2022). Review of evidence to support auk displacement and mortality rates in relation to offshore wind farms. APEM Scientific Report P00007416. Ørsted, January 2022.

2 Recommended displacement rates from MacArthur Green (2019a). Norfolk Vanguard Offshore Wind Farm. The Applicant Responses to First Written Questions. Appendix 3.3 – Operational Auk and Gannet Displacement: update and clarification.

3 Natural England recommended displacement and mortality rates for Gannet for Norfolk Vanguard Offshore Wind Farm.  MacArthur Green (2019b). Norfolk Vanguard Offshore Wind Farm Offshore Ornithology Assessment Update for Deadline 6.

4 Based on MS Scoping Opinion for Forth & Tay projects (2017).