Secondary mitigation and residual effect
  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.
Puffin

                        Magnitude of impact

  1. The estimated mortality resulting from displacement during operation and maintenance was assessed for each season, and also on an annual basis by combining seasonal impacts and comparing them against the largest regional seasonal population (as set out in volume 3, appendix 11.3, and summarised in Table 11.23   Open ▸ ).
  2. When using the displacement and mortality rates recommended by NatureScot, the predicted number of mortalities is 35 to 58 in the breeding season, and seven to 21 in the non-breeding season. This is an increase in the baseline mortality rate of 0.07% to 0.12% in the breeding season, and 0.02% to 0.05% in the non-breeding season. On an annual basis, the number of mortalities is 42 to 79, which is an increase in baseline mortality rates of 0.09% to 0.16% ( Table 11.23   Open ▸ ).
  3. Using the Applicant’s Approach, the predicted number of mortalities is 10 in the breeding season, and six in the non-breeding season. This is an increase in the baseline mortality rate of 0.02% in the breeding season, and 0.02% in the non-breeding season. On an annual basis, the number of mortalities is 16, which is an increase in baseline mortality rates of 0.03% ( Table 11.23   Open ▸ ).
  4. It should be noted that recent work using time-depth-recorders to monitor auk diving activity indicates that there is significant variation in diving behaviour (Dunn et al., 2024). The results presented by Dunn et al. (2024) indicate that the correction factors applied to account for auk availability bias (see volume 3, appendix 11.1) are likely to lead to overestimates of the true abundance of auks within the Array Study Area. Therefore, the number of mortalities predicted, based on the abundance of birds present, is also likely to be an overestimate and the conclusions must be considered highly precautionary.
  5. The impact is predicted to be of local spatial extent. The impact is expected to occur for the lifespan of the project, although is reversible following decommissioning of the project and is therefore considered to be of long-term duration. It is predicted that the impact will affect the receptor directly. However, even considering the NatureScot impact values, the increase in baseline mortality is expected to be below 1% and is unlikely to be detectable compared to natural variation in mortality rates. The magnitude of the impact is therefore deemed to be negligible.

 

Table 11.23:
Puffin Seasonal and Annual Displacement Estimates for the Array Plus 2 km Buffer During Operation and Maintenance

Table 11.23: Puffin Seasonal and Annual Displacement Estimates for the Array Plus 2 km Buffer During Operation and Maintenance

 

                        Sensitivity of the receptor

  1. Puffin are considered to be moderately vulnerable to displacement from offshore structures, being assigned a score of 3 (out of 5) by Wade et al. (2016).
  2. Puffin have a low reproductive potential (i.e. typically laying only one egg and not breeding until five years old) (Robinson, 2005). Given puffin nest in burrows, and often in inaccessible locations, abundance estimates are relatively infrequent. The long-term pattern indicates a population increase since the counts conducted for Operation Seafarer (1969/70) but small declines in recent years (JNCC, 2021; Burnell, 2023). Puffin is therefore assessed as having low potential for recovery.
  3. Puffin is a qualifying interest for several SPAs likely to be connected to the Array (within the mean-max + SD foraging range), with several non-SPA colonies also within range and so the species is considered to be of international value. The population recorded during baseline surveys of the Array was found to be of regional importance. Therefore, puffin is considered to be of international value.
  4. Puffin is deemed to be of medium vulnerability, limited potential recoverability and international value. The sensitivity of the receptor is therefore considered to be high.

                        Significance of the effect

  1. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
                        Secondary mitigation and residual effect
  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.
Fulmar

                        Magnitude of impact

  1. The estimated mortality resulting from displacement during operation and maintenance was assessed for each season, and also on an annual basis by combining seasonal impacts and comparing them against the largest regional seasonal population (as set out in volume 3, appendix 11.3, and summarised in Table 11.24   Open ▸ ).
  2. NatureScot (2023h) does not specify an alternative displacement or avoidance rate for fulmar due to the uncertainty surrounding the impact on the species.
  3. An Applicant’s Approach for fulmar was established due to the high abundances recorded during DAS of the Array, as well as the significant uncertainty surrounding displacement on fulmar, as reported by Wade et al (2016).
  4. Using the Applicant’s Approach range, the predicted number of mortalities is zero to seven in the pre-breeding season, zero to 19 in the breeding season, zero to six in the post-breeding season and zero to four in the non-breeding season. This is an increase in the baseline mortality rate of <0.001% to 0.003% in the pre-breeding, <0.001% to 0.018% in the breeding season, <0.001% to 0.003% in the post-breeding season and 0.001% to 0.003% in the non-breeding season. On an annual basis, the number of mortalities is zero to 36, which is an increase in baseline mortality rates of <0.001% to 0.02% ( Table 11.24   Open ▸ ).
  5. Using the Applicant’s Approach and placing focus on the 30% displacement rate, the predicted number of mortalities is one in the pre-breeding season, three in the breeding season, one in the post-breeding season and one in the non-breeding season. This is an increase in the baseline mortality rate of <0.001% in the pre-breeding, 0.003% in the breeding season, <0.001% in the post-breeding season and 0.001% in the non-breeding season. On an annual basis, the number of mortalities is six, which is an increase in baseline mortality rates of 0.003% ( Table 11.24   Open ▸ ).
  6. The impact is predicted to be of local spatial extent, long-term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. However, even considering the upper end of the range of impact values, the increase in baseline mortality is expected to be well below 1% and is unlikely to be detectable compared to natural variation in mortality rates. The magnitude is therefore, considered to be negligible.

 

Table 11.24:
Fulmar Seasonal and Annual Displacement Estimates for the Array Plus 2 km Buffer During Operation and Maintenance

Table 11.24: Fulmar Seasonal and Annual Displacement Estimates for the Array Plus 2 km Buffer During Operation and Maintenance

 

                        Sensitivity of the receptor

  1. In terms of behavioural response to wind farm structures, fulmar are considered have a very low vulnerability (Wade et al., 2016).
  2. Owing to their large foraging range, fulmar is a qualifying interest for several SPAs likely to be connected to the Array (within the mean-max + SD foraging range). Most of the world population is found in the UK and over 90% of the UK population is found on the Islands of Rum and Eigg (Scotland) and Skomer and Skokholm (Wales) (Mitchell et al., 2004; JNCC, 2020). The species is considered to be of international value.
  3. Fulmar has a low reproductive potential (i.e. only laying one egg and not breeding until nine years old; Robinson, 2005). There has been a moderate decline in the regional and national population of fulmar, with this likely due to a reduction in the amount of offal discarded from fishing vessels, reductions in natural prey and climate change (JNCC, 2020). The recoverability of the receptor is therefore, considered to be low.
  4. Fulmar is deemed to be of very low vulnerability, low recoverability and international value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

  1. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
                        Secondary mitigation and residual effect
  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.
Gannet

                        Magnitude of impact

  1. The estimated mortality resulting from displacement during operation and maintenance was assessed for each season, and also on an annual basis by combining seasonal impacts and comparing them against the largest regional seasonal population (as set out in volume 3, appendix 11.3, and summarised in Table 11.25   Open ▸ ).
  2. When using the displacement and mortality rates recommended by NatureScot, the predicted number of mortalities is zero to one in the pre-breeding season, 10 to 29 in the breeding season and five to 16 in the post-breeding season. This is an increase in the baseline mortality rate of <0.001% to 0.002% in the pre-breeding season, 0.01% to 0.02% in the breeding season and 0.01 to 0.02% in the post-breeding season. On an annual basis, the number of mortalities is 15 to 46, which is an increase in baseline mortality rates of 0.01% to 0.03% ( Table 11.23   Open ▸ ).
  3. Using the Applicant’s Approach, the predicted number of mortalities is zero in the pre-breeding season, 10 in the breeding season and five in the post-breeding season. This is an increase in the baseline mortality rate of <0.001% in the pre-breeding season, 0.01% in the breeding season and 0.01% in the post-breeding season. On an annual basis, the number of mortalities is 15, which is an increase in baseline mortality rates of 0.01% ( Table 11.23   Open ▸ ).
  4. The impact is predicted to be of local spatial extent, long-term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. However, even considering the upper end of the range of impact values, the increase in baseline mortality is expected to be well below 1% and is unlikely to be detectable compared to natural variation in mortality rates. The magnitude is therefore considered to be negligible.

 

Table 11.25:
Gannet Seasonal and Annual Displacement Estimates for the Array Plus 2 km Buffer During Operation and Maintenance

Table 11.25: Gannet Seasonal and Annual Displacement Estimates for the Array Plus 2 km Buffer During Operation and Maintenance

 

                        Sensitivity of the receptor

  1. In terms of behavioural response to offshore wind farm structures, gannet are considered to be of high vulnerability, with a score of four out of five assigned by Wade et al. (2016). During the breeding season, northern gannet show a strong avoidance of offshore wind farms (Peschko et al., 2021).
  2. Gannet have low reproductive potential given a typical age of first breeding of five years and typically laying only a single egg per breeding season. However, although gannet has a low reproductive potential, the species has demonstrated a consistent increasing trend in abundance since the 1990s (JNCC, 2020). It is of note that the species has suffered from the outbreak of avian flu during the 2022 breeding season (Pearce-Higgins et al., 2023), with declines of 25% recorded at certain sites in Britain in 2023 when compared against a pre-HPAI baseline (Tremlett et al., 2024). Therefore, whilst the overall population has shown steady growth, HPAI has led to some short-term declines. Therefore, overall gannet is deemed to have low recoverability.
  3. Due to the large foraging range, gannet is a qualifying interest for several SPAs likely to be connected to the Array (within the mean-max + SD foraging range), including the UK’s largest gannet colony at Bass Rock (refer to Table 6.30 of volume 3 appendix 11.1). The species is therefore considered to be of international value.
  4. Gannet is deemed to be of high vulnerability, low recoverability and international value. The sensitivity of the receptor is therefore considered to be high.

                        Significance of the effect

  1. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
                        Secondary mitigation and residual effect
  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.

Barrier to movement

  1. JNCC et al. (2022) defines barrier effects as “A barrier is a physical factor that limits the migration, or free movement of individuals or populations, thus requiring them to divert from their intended path in order to reach their original destination. This effect is expected to increase the energy expenditure of birds if they have to fly around the area in question in order to reach their goal”. It is typically considered to affect birds in flight only, either whilst they are on migration between breeding and wintering areas (for example) or between a breeding colony and a foraging area. The latter of these scenarios may impose an additional energetic cost to movements at a key period in the annual cycle when seabirds are making daily commutes between foraging grounds at sea and their breeding sites. Additional energetic costs could have long-term implications for individuals, impacting bird fitness (breeding productivity and survival) and for populations. Barrier effects are considered to be less impactful when affecting migratory flights, as avoidance of a single wind farm may be trivial relative to the total length and cost of the journey (Masden et al., 2010; 2012).
  2. Masden et al. (2010) found additional costs, expressed in relation to typical daily energetic expenditures, to be the highest per unit flight for seabirds with high wing loadings, such as gannets. For example, results suggest that increasing gannet flight distance by 2 km increases daily energetic cost by 1.25%. A 10 km increase may result in a 4.50% increase in daily energy expenditure. However, this is based on a foraging range of 160 km, where 10 km represents a 6.25% increase in distance flown. Scaling this to the mean maximum plus 1 SD foraging range of 709 km (Woodward et al., 2019), an additional flight distance of 10 km (4.5%) represents a scaled 1.02% increase in expenditure. This minimal increase in energy expenditure is unlikely to result in notable mortalities. Most importantly the authors found costs of extra flight to avoid a wind farm to appear to be much less than those imposed by low food abundance or adverse weather, although such costs will be additive to these.
  3. For breeding seabirds, NatureScot (2023h) consider barrier effects alongside displacement as “distributional responses”. This is because it can be difficult to distinguish barrier effects from the effects of displacement, for breeding seabirds foraging in the region. NatureScot (2023h) advise that distributional responses are assessed using the matrix approach, and therefore for breeding seabirds, no separate assessment of barrier to movement is carried out, with impacts considered to be included in the assessments carried out under the impact: Disturbance and Displacement from the Physical Presence of Wind Turbines and Maintenance Activities.
  4. This section therefore only considers the impact of the barrier to movement on migratory receptors such as those listed in Table 11.32   Open ▸ .

                        Operation and maintenance phase

                        Magnitude of impact

  1. In the absence of quantitative information available for individual species, the magnitude is considered qualitatively for all receptors.
  2. The diversion of flight lines as a result of a barrier effect created by the presence of the Array for migratory birds is considered less of an impact than for those barrier effects to daily foraging flights. Speakman et al. (2009) and Masden et al. (2010; 2012) calculated that the costs of one-off avoidances during migration were small, accounting for less than 2% of available fat reserves.
  3. The impact is predicted to be of local spatial extent, long-term duration, continuous and reversible. It is predicted that the impact will affect the receptor directly. Due to the likely absence of any detectable impact on the fitness of individuals and the demography of the populations, the magnitude is therefore considered to be negligible.

                        Sensitivity of the receptor

  1. Migratory birds are deemed to be of low vulnerability, low to high recoverability and regional to international value. The sensitivity of the receptor is therefore considered to be low to high.

                        Significance of the effect

  1. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be low to high. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.
                        Secondary mitigation and residual effect
  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.

Collision with wind turbines

  1. During the operation and maintenance phase of the Array, the turning rotors of the wind turbines may present a risk of collision for seabirds. Stationary structures, such as the tower, nacelle or when rotors are not operating, are not expected to result in a material risk of collision. When a collision occurs between the turning rotor blade and the bird, it is assumed to result in direct mortality of the bird, which potentially could result in population level impacts.
  2. The ability of seabirds to detect and manoeuvre around wind turbine blades is a factor that is considered when modelling and assessing the risk. In response to this, it is standard practice to calculate differing levels of avoidance for different species or species groups. Avoidance rates are applied to CRMs to predict levels of impact more realistically, based on available literature and expert advice about seabird behaviour and their flight response to wind turbines.
  3. Species differ in their susceptibility to collision risk, depending on their flight behaviour and avoidance responses, and the vulnerability of their populations (Bradbury et al. 2014; Wade et al., 2016). As sensitivity to collision differs considerably between species, species were screened and progressed for assessment of significance on the basis of the importance of the population of each species recorded within the Array offshore ornithology study area and consideration of their perceived risk from collision (Bradbury et al., 2014; Wade et al., 2016).
  4. Four regularly occurring seabird species were identified as potentially at risk of collision due to their recorded abundance in the Array offshore ornithology study area and their high vulnerability to collision (Bradbury et al., 2014; Wade et al., 2016): kittiwake, herring gull, lesser black-backed gull and gannet. Furthermore, fulmar was included in the collision risk assessment due to its high abundances recorded within the Array. Wade et al. (2016) highlighted the high uncertainty surrounding fulmar vulnerability to collision, despite Bradbury et al. (2014) classifying them as having a low vulnerability to collision impacts.
  5. Species included were therefore kittiwake, herring gull, lesser black-backed gull, gannet and fulmar. Modelling for these species is provided in volume 3, appendix 11.2. Additionally, consideration was given to species that may not have been accurately captured during traditional baseline DAS. This included migratory seabirds and waterbirds, with modelling for these species groups provided in volume 3, appendix 11.2, annex B.
  6. The magnitude of change was determined by calculating the estimated number of collisions with the wind turbines and the resulting percentage increase in the background mortality rate of the relevant regional population.
  7. There is the potential that aviation and navigation lighting on wind turbines might attract seabirds and thus increase the risk of collision. Conversely, aviation and navigation lighting could deter birds from moving through the Array. To our knowledge there is little published evidence showing the effects of lighting on seabird collision and displacement. Earlier work on seaducks by Desholm and Kahlert (2005) showed that migrating flocks were more prone to enter the wind farm. However, the higher risk of collision in the dark was counteracted by increasing distance from individual turbines and flying in the corridors between turbines. For true seabirds, there is published evidence showing that seabirds are less active at night compared to daytime (Furness et al., 2018). Wade et al. (2016) ranked vulnerability of seabirds to collision by accounting for the nocturnal activity rate of seabirds. A recent review highlighted that certain species of birds (especially those that nest underground such as shearwaters and petrel species) are often attracted to powerful light sources (Deakin et al., 2022). However, in the examples given, the light sources to which birds were attracted are significantly brighter than the lights associated with an offshore wind farm. Lights on offshore structures, including offshore wind turbines must comply with minimum requirements as set out in the International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) Recommendation O-117 on ‘The Marking of Offshore Wind Farms’ for navigation lighting and by the Civil Aviation Authority in the Air Navigation Orders (CAP 393 and guidance in CAP 764). Such lighting is not comparable to the examples given in Deakin et al. (2022) and it is therefore considered unlikely that attraction will occur.
  8. CRM for regularly occurring species was undertaken using the Stochastic Collision Risk Model (sCRM) developed by Marine Scotland (McGregor et al., 2018). The User Guide for the sCRM Shiny App provided by Marine Scotland (Donovan, 2017) has been followed for the modelling of collision impacts predicted for the Array. The full methodology and results are provided in volume 3, appendix 11.2.
  9. For all regularly occurring species, the assessment has been carried out on the basis of the input parameters recommended by NatureScot (2023g). However, it should be noted that there is considerable uncertainty around several of the key input parameters, including flight speed and avoidance rates. Therefore, in addition to the assessment value, a range of other input parameters has also been considered, as detailed in volume 3, appendix 11.2. The minimum and maximum collision estimates from this range are also presented. However, these do not represent the Applicant’s position and only highlight the level of uncertainty surrounding the NatureScot advocated rates. Adopting an 'Applicant's Approach' as undertaken for displacement would involve employing the same rates as recommended by NatureScot, which would yield identical results and thus are not presented separately.
  10. Volume 3, appendix 11.2 presents the results of the Band model Options 2 and 3[15].However, it should be noted that recent NatureScot advice has indicated that Option 3 (and 4) will no longer be required (refer to Table 11.3   Open ▸ ). Therefore, although Options 2 and 3 are presented on volume 3, appendix 11.2, this assessment will only use Option 2 values.
  11. It is acknowledged that migratory passage movements may not be adequately captured by traditional survey methods. Therefore, the SOSS Migration Assessment Tool (SOSSMAT) was used to assess the population size of migratory bird species designated as features of the UK SPA network that may cross the Array; instructions are given in Wright et al. (2012).
  12. The resulting number of migratory seabirds and waterbirds estimated to cross the Array was inputted into the Band (2012) single transit CRM.
  13. The methodology and detailed results of the CRM for 56 migratory waterbirds and seabirds are provided in volume 3, appendix 11.2, annex B.

                        Operation and maintenance phase

Kittiwake

                        Magnitude of impact

  1. When using the parameters recommended by NatureScot (2023g) the predicted number of kittiwake mortalities is 6.24 individuals in the pre-breeding season, 28.13 individuals in the breeding season and 5.35 individuals in the post-breeding season. This is an increase in the baseline mortality rate of 0.01% in the pre-breeding season, 0.07% in the breeding season and 0.004% in the post-breeding season. On an annual basis, the number of mortalities is 39.72 individuals, which is an increase in baseline mortality rates of 0.03% ( Table 11.26   Open ▸ ).
  2. Using the range, the predicted number of kittiwake mortalities is 1.44 to 6.24 individuals in the pre-breeding season, 6.51 to 28.13 individuals in the breeding season and 1.24 to 5.35 individuals in the post-breeding season. This is an increase in the baseline mortality rate of 0.001% to 0.01% in the pre-breeding season, 0.02% to 0.07% in the breeding season and 0.001% to 0.004% in the post-breeding season. On an annual basis, the number of mortalities is 9.19 to 39.72 individuals, which is an increase in baseline mortality rates of 0.03% ( Table 11.26   Open ▸ ).
  3. The impact is predicted to be of local spatial extent. The impact is expected to occur for the lifespan of the project, although is reversible following decommissioning of the project and is therefore considered to be of long-term duration. It is predicted that the impact will affect the receptor directly. Using both the Applicant's range and the rates recommended by NatureScot (2023g), the increase in mortality is below 1% of baseline mortality in each season and also on an annual basis. Therefore, the magnitude of impact is considered to be negligible.

 

Table 11.26:
Assessment of Predicted Collision Risk Estimates for Kittiwake on Seasonal and Annual Bases Against the Baseline Mortality of Relevant Regional Populations

Table 11.26: Assessment of Predicted Collision Risk Estimates for Kittiwake on Seasonal and Annual Bases Against the Baseline Mortality of Relevant Regional Populations

 

                        Sensitivity of the receptor

  1. Kittiwake was rated as highly vulnerable to collision impacts by Wade et al. (2016), due to the proportion of flights likely to occur at potential risk height and percentage of time in flight. In terms of nocturnal activity rate, kittiwake are considered to have a medium rate of activity at night with a score of three (out of five) (Wade et al. 2016).
  2. Kittiwake lay two eggs and breed from the age of three onwards, typically living on average for 12 years (Burnell et al., 2023). Kittiwake have undergone decreases of approximately 57% in Scotland since the early 2000s. Surveys managed by the RSPB in 2023 have recorded indicative increases of 8% across a number of sites in Britain in 2023 when compared against a pre-HPAI baseline (Tremlett et al., 2024). Overall, kittiwake is deemed to have low recoverability.
  3. Kittiwake is a qualifying interest for several SPAs likely to be connected to the Array (within the mean-max + SD foraging range), with several non-SPA colonies also within range and so the species is considered to be of international conservation value. Refer to Table 6.2 of volume 3, appendix 11.1 for details of SPAs with connectivity to the Array with regards to kittiwake.
  4. Kittiwake is deemed to be of high vulnerability, low recoverability and international value. The sensitivity of the receptor is therefore considered to be high.

                        Significance of the effect

  1. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
                        Secondary mitigation and residual effect
  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.
Herring gull

                        Magnitude of impact

  1. When using the parameters recommended by NatureScot,(2023g) the predicted number of herring gull mortalities is <0.01 individuals in the breeding season and 2.74 individuals in the non-breeding season. This is an increase in the baseline mortality rate of <0.001% in the breeding season and 0.003% in the non-breeding season. On an annual basis, the number of mortalities is 2.74 individuals, which is an increase in baseline mortality rates of 0.003% ( Table 11.27   Open ▸ ).
  2. Using the range, the predicted number of herring gull mortalities is <0.01 individuals in the breeding season and 1.20 to 2.74 individuals in the non-breeding season. This is an increase in the baseline mortality rate of <0.001% in the breeding season and 0.002% to 0.003% in the non-breeding season. On an annual basis, the number of mortalities is 1.20 to 2.74 individuals, which is an increase in baseline mortality rates of 0.002% to 0.003% ( Table 11.27   Open ▸ ).
  3. The impact is predicted to be of local spatial extent. The impact is expected to occur for the lifespan of the project, although is reversible following decommissioning of the project and is therefore considered to be of long-term duration. It is predicted that the impact will affect the receptor directly. Using both the Applicant's range and the rates recommended by NatureScot (2023g), the increase in mortality is below 1% of baseline mortality in each season and also on an annual basis. Therefore, the magnitude of impact is considered to be negligible.
Table 11.27:
Assessment of Predicted Collision Risk Estimates for Herring Gull on Seasonal and Annual Bases Against the Baseline Mortality of Relevant Regional Populations

Table 11.27: Assessment of Predicted Collision Risk Estimates for Herring Gull on Seasonal and Annual Bases Against the Baseline Mortality of Relevant Regional Populations

 

                        Sensitivity of the receptor

  1. Herring gull was rated as one of the most vulnerable seabird species to collision impacts by Wade et al. (2016), due to the proportion of flights likely to occur at potential risk height and percentage of time in flight. In terms of nocturnal activity rate, herring gull are considered to have a medium rate of activity at night with a score of three (out of five) (Wade et al. 2016).
  2. As herring gull is a qualifying interest for several SPAs likely to be connected to the Array (within the mean-max + SD foraging range) with multiple non-SPA colonies within range, the species is considered to be of international value. Refer to Table 6.7 of volume 3, appendix 11.1 for details of SPAs with connectivity to the Array with regards to herring gull.
  3. Herring gull lay up to three eggs and breed from the age of four onwards, typically living on average for 12 years (Burnell et al., 2023). Natural nesting colonies of herring gull have undergone decreases of approximately 44% in Scotland since the early 2000s, whereas urban-nesting populations have increased considerably. Given that the urban population is small compared to the natural population (Burnell et al., 2023), the overall trend is likely to be a decline. Surveys managed by the RSPB in 2023 have recorded indicative declines of 7% across a number of sites in Britain in 2023 when compared against a pre-HPAI baseline (Tremlett et al., 2024). Overall herring gull is considered to have low recoverability.
  4. Herring gull is deemed to be of very high vulnerability, low recoverability and international value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

  1. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
                        Secondary mitigation and residual effect
  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.
Lesser black-backed gull

                        Magnitude of impact

  1. When using the parameters recommended by NatureScot (2023g) the predicted number of lesser black-backed gull mortalities is <0.01 individuals in the pre-breeding season, 0.26 individuals in the breeding season and <0.01 individuals in the post-breeding season. This is an increase in the baseline mortality rate of <0.001% in the pre-breeding season, 0.01% in the breeding season and <0.001% in the post-breeding season. On an annual basis, the number of mortalities is 0.26 individuals, which is an increase in baseline mortality rates of 0.001% ( Table 11.28   Open ▸ ).
  2. Using the range, the predicted number of lesser black-backed gull mortalities is <0.01 individuals in the pre-breeding season, 0.11 to 0.26 individuals in the breeding season and <0.01 individuals in the post-breeding season. This is an increase in the baseline mortality rate of <0.001% in the pre-breeding season, 0.003% to 0.006% in the breeding season and <0.001% in the post-breeding season. On an annual basis, the number of mortalities is 0.11 to 0.26 individuals, which is an increase in baseline mortality rates of <0.001% to 0.001% ( Table 11.28   Open ▸ ).
  3. The impact is predicted to be of local spatial extent. The impact is expected to occur for the lifespan of the project, although is reversible following decommissioning of the project and is therefore considered to be of long-term duration. It is predicted that the impact will affect the receptor directly. Using both the Applicant's range and the rates recommended by NatureScot (2023g), the increase in mortality is below 1% of baseline mortality in each season and also on an annual basis. Therefore, the magnitude of impact is considered to be negligible.

 

Table 11.28:
Assessment of Predicted Collision Risk Estimates for Lesser Black-backed Gull on Seasonal and Annual Bases Against the Baseline Mortality of Relevant Regional Populations

Table 11.28: Assessment of Predicted Collision Risk Estimates for Lesser Black-backed Gull on Seasonal and Annual Bases Against the Baseline Mortality of Relevant Regional Populations

 

                        Sensitivity of the receptor

  1. Lesser black-backed gull was rated as one of the most vulnerable seabird species to collision impacts by Wade et al. (2016), due to the proportion of flights likely to occur at potential risk height and percentage of time in flight. In terms of nocturnal activity rate, lesser black-backed gull are considered to have a medium rate of activity at night with a score of three (out of five) (Wade et al. 2016).
  2. As lesser black-backed gull is a qualifying interest for several SPAs likely to be connected to the Array (within the mean-max + SD foraging range), with multiple non-SPA colonies within range, the species is considered to be of international conservation value. Refer to Table 6.9 of volume 3, appendix 11.1 for details of SPAs with connectivity to the Array with regards to lesser black-backed gull.
  3. Lesser black-backed gull lay an average of three eggs and breed from the age of four onwards, typically living on average for 15 years (Burnell et al., 2023). Coastal colonies of lesser black-backed gull have undergone decreases of approximately 61% in Scotland since the early 2000s, whereas inland populations have increased by 145%. Whilst the urban population of lesser black-backed gulls is increasing, the much larger natural population is declining and therefore the overall national trend is one of decline, with an overall decline of 48% (Burnell et al., 2023). Surveys managed by the RSPB in 2023 have recorded indicative declines of 25% across a number of sites in Britain in 2023 when compared against a pre-HPAI baseline (Tremlett et al., 2024). Overall lesser black-backed gull is considered to have low recoverability.
  4. Lesser black-backed gull is deemed to be of very high vulnerability, low recoverability and international value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

  1. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
                        Secondary mitigation and residual effect
  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.
Fulmar

                        Magnitude of impact

  1. When using the parameters recommended by NatureScot (2023g) and the Applicant’s range, the predicted number of fulmar mortalities is 1.99 individuals in the pre-breeding season, 2.13 individuals in the breeding season, 0.19 individuals in the post-breeding season and 0.46 individuals in the non-breeding season. This is an increase in the baseline mortality rate of 0.001% in the pre-breeding season, 0.002% in the breeding season, <0.001% in the post-breeding season and <0.001% in the non-breeding season. On an annual basis, the number of mortalities is 4.77 individuals, which is an increase in baseline mortality rates of 0.002% ( Table 11.29   Open ▸ ).
  2. The impact is predicted to be of local spatial extent. The impact is expected to occur for the lifespan of the project, although is reversible following decommissioning of the project and is therefore considered to be of long-term duration. It is predicted that the impact will affect the receptor directly. Using both the Applicant's range and the rates recommended by NatureScot (2023g), the increase in mortality is below 1% of baseline mortality in each season and also on an annual basis. Therefore, the magnitude of impact is considered to be negligible.

Table 11.29:
Assessment of Predicted Collision Risk Estimates for Fulmar on Seasonal and Annual Bases Against the Baseline Mortality of Relevant Regional Populations

Table 11.29: Assessment of Predicted Collision Risk Estimates for Fulmar on Seasonal and Annual Bases Against the Baseline Mortality of Relevant Regional Populations

 

                        Sensitivity of the receptor

  1. Fulmar are considered to have very low vulnerability to collision with wind turbines (Wade et al., 2016) and have been included on a precautionary basis due to a high uncertainty score in Wade et al. (2016).
  2. Fulmar is a qualifying interest for several SPAs likely to be connected to the Array (within the mean-max + SD foraging range). The species is therefore considered to be of international value. Refer to Table 6.26 of volume 3, appendix 11.1 for details of SPAs with connectivity to the Array with regards to fulmar.
  3. Fulmar has a low reproductive potential, due to laying a single egg per breeding attempt, and typical age of recruitment of nine years. Fulmar populations have been declining in recent years (JNCC, 2020). Fulmar is therefore considered to have low recoverability.
  4. Fulmar is deemed to be of low vulnerability, low recoverability and international value. The sensitivity of the receptor is therefore considered to be high.

                        Significance of the effect

  1. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
                        Secondary mitigation and residual effect
  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.
Gannet

                        Magnitude of impact

  1. When using the parameters recommended by NatureScot (2023g) the predicted number of gannet mortalities is 0.24 individuals in the pre-breeding season, 28.18 individuals in the breeding season and 3.76 individuals in the post-breeding season. This is an increase in the baseline mortality rate of 0.001% in the pre-breeding season, 0.02% in the breeding season and 0.004% in the post-breeding season. On an annual basis, the number of mortalities is 32.18 individuals, which is an increase in baseline mortality rates of 0.02% ( Table 11.30   Open ▸ ).
  2. Using the range, the predicted number of gannet mortalities is 0.23 to 0.24 individuals in the pre-breeding season, 27.30 to 28.18 individuals in the breeding season and 3.61 to 3.76 individuals in the post-breeding season. This is an increase in the baseline mortality rate of 0.001% in the pre-breeding season, 0.02% in the breeding season and 0.004% in the post-breeding season. On an annual basis, the number of mortalities is 31.14 to 32.18 individuals, which is an increase in baseline mortality rates of 0.02% ( Table 11.30   Open ▸ ).
  3. It should further be noted that there is strong evidence that gannet avoid OWFs to a significant extent (Garthe and Hüppop, 2004; Furness and Wade, 2012; Pavat et al., 2023), and this “macro avoidance” is not captured by the method used to calculate avoidance rates for CRM (Ozsanlav-Harris et al., 2023). Therefore, the collision estimates provided are likely to be significant overestimates.
  4. The impact is predicted to be of local spatial extent. The impact is expected to occur for the lifespan of the project, although is reversible following decommissioning of the project and is therefore considered to be of long-term duration. It is predicted that the impact will affect the receptor directly. Using both the Applicant's range and the rates recommended by NatureScot (2023g), the increase in mortality is below 1% of baseline mortality in each season and also on an annual basis. Therefore, the magnitude of impact is considered to be negligible.

 

Table 11.30:
Assessment of Predicted Collision Risk Estimates for Gannet on Seasonal and Annual Bases Against the Baseline Mortality of Relevant Regional Populations

Table 11.30: Assessment of Predicted Collision Risk Estimates for Gannet on Seasonal and Annual Bases Against the Baseline Mortality of Relevant Regional Populations

 

                        Sensitivity of the receptor

  1. Although the latest scientific guidance showed the species to display a high level of macro-avoidance (Peschko et al., 2020), the species is rated as relatively vulnerable to collision impacts by Wade et al. (2016).
  2. Gannet is a qualifying interest for several SPAs likely to be connected to the Array (within the mean-max + SD foraging range). The species is therefore considered to be of international value. Refer to Table 6.30 of volume 3, appendix 11.1 for details of SPAs with connectivity to the Array with regards to gannet.
  3. Gannet have low reproductive potential given a typical age of first breeding of five years and typically laying only a single egg per breeding season. However, although gannet has a low reproductive potential, the species has demonstrated a consistent increasing trend in abundance since the 1990’s (JNCC, 2020).. It is of note that the species has suffered from the outbreak of avian flu during the 2022 breeding season (Pearce-Higgins et al., 2023), with declines of 25% recorded at certain sites in Britain in 2023 when compared against a pre-HPAI baseline (Tremlett et al., 2024). Therefore, whilst the overall population has shown steady growth, HPAI has led to some short-term declines. Therefore, overall gannet is deemed to have low recoverability.
  4. Gannet is deemed to be of high vulnerability, low recoverability and international value. The sensitivity of the receptor is therefore considered to be high.

                        Significance of the effect

  1. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
                        Secondary mitigation and residual effect
  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.
Migratory birds

                        Magnitude of impact

  1. It is recognised that migratory birds may not be adequately characterised by the site-specific DAS carried out at the Array. Migratory birds may fly at night (when no DAS are carried out) or in pulse movements which could easily be missed by DAS, as they are conducted on a monthly basis. Therefore, the risk to migratory birds cannot be assessed using the same methodology as has been applied for regularly occurring seabirds (above). Instead, the potential effect on migratory birds has been assessed using a qualitative approach drawing on available resources (principally Woodward et al., 2023), as well as a quantitative approach, using the Strategic Ornithological Support Services Migration Assessment Tool (SOSSMAT) (Wright et al., 2012).
  2. Woodward et al. (2023) provide a review of available information regarding to migratory birds in Scottish waters and the potential for collision risk. Key information compiled includes population estimates, migratory routes, timing of migration, migratory flight heights, migratory flight speeds, and migratory avoidance rates and behaviour. Woodward et al. (2023) compile this information for 69 species or sub-species, which are non-seabird features of Special Protection Areas (SPAs) including swans, geese, ducks, waders, raptors and other non-passerines. A summary of the key information for each species considered is given in Table 11.31   Open ▸ .
  3. For all species, the impact is predicted to be of local spatial extent, long-term duration, continuous and high reversibility. It is predicted that the impact will affect the receptor directly. Based on the information in Woodward et al. (2023) and summarised in Table 11.31   Open ▸ , 55 species have connectivity to the Array on migration and therefore are potentially at risk from collision. Of these, due to very high avoidance rate (>0.99), the magnitude of impact is expected to be negligible for 33 species. For the remaining 22 species, the recommended avoidance rate was high but not very high (between 0.98 and 0.99) and therefore on a highly precautionary basis the expected magnitude of impact is deemed to be low following this qualitative approach to assessment.
  4. In addition, a quantitative assessment of collision risk to migratory birds has been carried out using SOSSMAT (Wright et al. 2012). The Applicant is aware that a new quantitative migration collision risk model (mCRM) is under development, but this model is currently undergoing testing and seeking approval, and therefore not yet ready to be used for assessment (mCRM Authors, 2021) at the time of writing this chapter (April 2024). The SOSSMAT therefore represents the best available tool currently available to provide quantitative estimates of the collision risk to migratory birds. An assessment using a range of avoidance rates for collision risk to migratory birds has been carried out and provided in volume 3, appendix 11.2, annex B. A summary of the results are presented in Table 11.32   Open ▸ .
  5. At the default recommended avoidance rate of 98% by SNH guidance (SNH, 2010), all of the predicted collision mortalities are well below a 0.005 percentage point increase in mortality rate. This level of impact would be negligible and would not be distinguishable from natural variation.
  6. The impact is predicted to be of local spatial extent, long-term duration, continuous and high reversibility. It is predicted that the impact will affect the receptor directly. Under this approach, the magnitude for all species is therefore considered to be negligible.

 

Table 11.31:
Assessment of Collision Risk to Migratory Species based on Woodward et al. (2023)

Table 11.31: Assessment of Collision Risk to Migratory Species based on Woodward et al. (2023)

 

Table 11.32:
Quantitative Assessment of Collision Risk to Migratory Species Using SOSSMAT (Wright et al., 2012) and the Band (2012) CRM

Table 11.32: Quantitative Assessment of Collision Risk to Migratory Species Using SOSSMAT (Wright et al., 2012) and the Band (2012) CRM

                        Sensitivity of the receptor

  1. Although migratory waterbirds have not been significantly studied in the offshore environment, vulnerability to collisions is likely to be generally low, since most migration will occur on a broad front and also above rotor height, although during periods of poor weather this risk may increase.
  2. Recoverability of populations of migrants may vary considerably, with smaller wader species with a relatively favourable conservation status (e.g. dunlin) faring better than larger species with lower reproductive rates (e.g. Eurasian curlew).
  3. Migratory birds are deemed to be of low to medium vulnerability, low to high recoverability and local to international value. On a precautionary basis and purposes of this assessment these species are assumed to have high sensitivity to collision (i.e. medium vulnerability, low recoverability and international value).

                        Significance of the effect

  1. Using a qualitative approach and the information presented in Woodward et al. (2023), it was found that the magnitude of impact was expected to be negligible to low. However, this qualitative approach is limited in its ability to accurately predict the magnitude of impact, as it does not provide an estimate of the number of birds likely to be subject to mortality. The prediction of a low magnitude of impact is therefore highly precautionary, as an impact of that magnitude could not be ruled out on the basis of the information presented.
  2. This qualitative approach is therefore supplemented with a quantitative approach, using the SOSSMAT (Wright et al., 2012). Whilst it is recognised that significant work has been carried out since the SOSSMAT was developed, until the new mCRM tool is approved for use, SOSSMAT remains the best available tool to quantitatively assess collision risk to migratory birds. Using SOSSMAT, it is evident that the numbers of birds subject to collision mortality are, for all species, zero or negligible. It should also be noted that this conclusion is based on an avoidance rate of 0.98 for all species, while the more recent review (Woodward et al., 2023) suggests a higher avoidance rate (0.9851 to 0.9998; Table 11.31   Open ▸ ) for all species, and therefore the collision estimates in Table 11.32   Open ▸ are highly precautionary.
  3. Therefore, based on considering both the qualitative and quantitative approaches to assessment, the magnitude of the impact is deemed to be negligible (for all species) and the sensitivity of the receptor is considered to be high (based on a precautionary basis). The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms for any species.

                        Secondary mitigation and residual effect

  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.

Changes to prey availability

  1. Changes to prey availability may occur as a result of construction and decommissioning activities, especially those that disturb the seabed. During the operational phase, changes to prey availability are expected to be minimal. However, as requested by NatureScot ( Table 11.3   Open ▸ ), changes to prey availability have been considered for all phases.

                        Construction phase

                        Magnitude of impact

  1. A number of potential impacts on benthic subtidal ecology (including benthic invertebrate prey) associated with the Array were identified in volume 2, chapter 8, including disturbance during construction. The assessment identified an effect of minor adverse significance as a result of disturbance during construction, which is not significant in EIA terms.
  2. With regards to fish and shellfish prey, volume 2, chapter 9 considered the potential impacts on marine species (including shellfish), sandeel, herring and diadromous fish of disturbance during construction. The assessment identified an effect of minor adverse significance on all fish and shellfish receptors as a result of disturbance during construction, which is not significant in EIA terms.
  3. Based on the information presented in volume 2, chapters 8 and 9, the direct impact of construction noise on fish and mobile invertebrates is expected to be of minor adverse significance. Construction works will be spatially and temporally restricted, covering only a small portion of the site at any given time. Construction impacts are restricted to the duration of the construction phase, and once construction has finished, the adverse impacts will cease and any change on prey species is likely to be reversed. The impact on ornithological receptors is predicted to be of local spatial extent, medium duration, intermittent and reversible. The magnitude is therefore considered to be of negligible significance.

                        Sensitivity of the receptor

  1. None of the VORs considered in this assessment are highly specialist. All VORs have a moderate degree of flexibility in their habitat preferences and prey items (Del Hoyo et al., 1992). VORs vary in their recoverability from low to high and population status from local to international. Therefore, sensitivity of the receptors overall is assessed as ranging from low to high.

                        Significance of the effect

  1. Given a magnitude of impact of negligible, and a sensitivity ranging from low to high, the significance of the effect is concluded to be of negligible to minor adverse significance, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.

                        Operation and maintenance phase

                        Magnitude of impact

  1. The impact is predicted to be of local spatial extent, long-term duration, irregular and high reversibility. Operation and maintenance works will be spatially and temporally restricted, covering only a small portion of the site at any given time. It is predicted that the impact will affect the receptor indirectly. The magnitude is therefore considered to be negligible.
  2. The assessment in volume 2, chapter 8 considered the potential impacts on benthic subtidal ecology (including benthic invertebrate prey) associated with the Array during operation and maintenance to be of minor adverse significance, which is not significant in EIA terms.
  3. With regards to fish and shellfish prey, volume 2, chapter 9 considered the potential impacts on marine species (including shellfish), sandeel, herring and diadromous fish during operation and maintenance to be of minor adverse significance, which is not significant in EIA terms.
  4. Based on the information presented in volume 2, chapters 8 and 9, the direct impact of operation and maintenance on fish and mobile invertebrates (i.e. prey) is expected to be of minor adverse significance. The impact on ornithological receptors is predicted to be of local spatial extent, long-term but short-duration, intermittent and reversible. The magnitude is therefore considered to be of negligible significance.

                        Sensitivity of the receptor

  1. None of the VORs considered in this assessment are highly specialist. All VORs have a moderate degree of flexibility in their habitat preferences and prey items (Del Hoyo et al., 1992). VORs vary in their recoverability from low to high and population status from local to international. Therefore, sensitivity of the receptors overall is assessed as ranging from low to high.

                        Significance of the effect

  1. Given a magnitude of impact of negligible, and a sensitivity ranging from low to high, the significance of the effect is concluded to be of negligible to minor adverse significance, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.

                        Decommissioning phase

  1. The MDS for the decommissioning phase is assumed to be equal to the construction phase ( Table 11.11   Open ▸ ). As such, the assessment of the effects is the same and is not repeated here. Therefore, as concluded in the construction phase, the effect of changes to prey availability in the decommissioning phase is not significant in EIA terms.

Entanglement

  1. There is a risk to diving seabirds of becoming entangled in submerged ropes, chains and cables whilst foraging underwater. This risk can be split into “primary entanglement” in which the bird becomes entangled in ropes, chains and cables deployed as part of the Array, and also “secondary entanglement”, in which the bird becomes entangled in drifting debris (primarily fishing gear) that has become snagged on infrastructure associated with the Array. If seabirds become entangled, it is likely to lead to injury and death.
  2. The ornithological features considered to be at risk from entanglement are those diving seabirds established to be present in the Array (i.e. guillemot, razorbill, puffin and gannet; refer to Table 4.1 of volume 3 appendix 11.1 for vulnerability to drowning).

                        Operation and maintenance phase

                        Magnitude of impact

  1. The risk from primary entanglement is deemed to be very low, because the diameter, weight and tension of mooring lines and cables associated with floating wind farms means they are physically unlikely to entangle seabirds (SEER, 2022).
  2. Secondary entanglement is the more likely pathway for seabirds getting entangled, as drifting fishing gear has characteristics (such as netting or free-floating fishing line) that make entanglement of diving seabirds more likely. Currently, however, there is very little evidence that secondary entanglement of seabirds occurs with any frequency (SEER, 2022). If secondary entanglement was a high risk to seabirds, it is expected that it would have been detected and reported in relation to other offshore deployments including oil and gas platforms (Benjamins et al., 2014).
  3. Furthermore, the operation and maintenance schedule for the Array will include measures to detect and remove accumulations of debris, as is standard practice for floating offshore wind farms (Kincardine Offshore Windfarm, 2016; Pentland Floating Offshore Wind Farm, 2022). This will further reduce the risk of entanglement.
  4. The impact is predicted to be of local spatial extent, long-term duration, continuous and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be negligible.

                        Sensitivity of the receptor

  1. For all ornithological features considered, it is assumed that entanglement would be potentially fatal for the individual concerned. The sensitivity to entanglement is likely to depend on both behavioural characteristics, sensory characteristics and physical characteristics, all of which may influence the probability of encountering debris and subsequently becoming entangled in it (Benjamins et al., 2014). The framework Benjamins et al. (2014) developed for marine megafauna would appear to suggest the ornithological features (i.e. seabirds) associated with the Array are less sensitive to entanglement due to their small size, relatively flexible bodies, good underwater vision and pursuit hunting mode of foraging.
  2. Guillemot, razorbill, puffin are deemed to be of high vulnerability to entanglement (as set out in Table 4.1 of volume 3 appendix 11.1, indicated as vulnerability to drowning) and gannet is considered to be of medium vulnerability to entanglement.
  3. As set out in Table 11.19   Open ▸ , guillemot, puffin and gannet are of low recoverability and international value. Razorbill is of medium recoverability and international value. The sensitivity of all four receptors is therefore considered to be high.

                        Significance of the effect

  1. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

  1. No offshore ornithology secondary mitigation is considered necessary because the likely effect in the absence of mitigation is not significant in EIA terms.

Combined Impact – Collision and Displacement

  1. Three species are considered to be at risk from both displacement and collision during the operation and maintenance phase. These are kittiwake, fulmar and gannet. To better understand the magnitude of the potential impact on these species, the predicted effects of both collision and displacement have been combined.
  2. It is recognised that assessing these two potential impacts together could amount to double counting, as birds that are subject to displacement could not be subject to potential collision risk as they are already assumed to have not entered the Array. Equally, birds estimated to be subject to collision risk mortality would not be subjected to displacement mortality as well. The results presented in this section are therefore considered highly precautionary, especially for species with high displacement rates (i.e. gannet).
  3. Currently, no more refined method to consider displacement and collision together has been agreed with NatureScot and therefore the precautionary and highly unlikely additive approach is presented in this assessment.

                        Operation and maintenance phase