11. Offshore Ornithology

11.1.   Introduction

11.1. Introduction

1. This chapter of the Array Environmental Impact Assessment (EIA) Report presents the assessment of the likely significant effects (LSE1) (as per the EIA Regulations) on offshore ornithology as a result of the Ossian Array which is the subject of this application (hereafter referred to as “the Array”). Specifically, this chapter considers the potential impacts of the Array on offshore ornithology during the construction, operation and maintenance, and decommissioning phases.
2. The following technical chapters also inform the assessment presented in this chapter:

• volume 2, chapter 8: Benthic Subtidal Ecology; and
• volume 2, chapter 9: Fish and Shellfish Ecology.

3. This chapter relies upon information contained within:

• volume 3, appendix 11.1: Offshore Ornithology Baseline Characterisation Technical Report;

-        annex A: Offshore Ornithology Design-Based Abundance Estimates;

-        annex B: Offshore Ornithology MRSea Abundance Estimates;

-        annex C: Offshore Ornithology Colony Counts for Breeding Season Regional Populations;

-        annex D: Offshore Ornithology Apportioned Design-Based Abundance Estimates;

• volume 3, appendix 11.2: Offshore Ornithology Collision Risk Model (CRM) Technical Report;

-        annex A: Offshore Ornithology Deterministic CRM Estimates;

-        annex B: Offshore Ornithology Migratory CRM Estimates;

• volume 3, appendix 11.3: Offshore Ornithology Displacement Technical Report;

-        annex A: Offshore Ornithology Displacement Data;

• volume 3, appendix 11.4: Offshore Ornithology MRSea Technical Report;

-        annex A: Offshore Ornithology MRSea Validation Methodology;

-        annex B: Offshore Ornithology MRSea and Design-Based Abundance Estimates Comparison;

• appendix 11.5: Offshore Ornithology Population Viability Analysis (PVA) Technical Report.

11.2.   Purpose of the Chapter

11.2. Purpose of the Chapter

4. The Array EIA Report provides the Scottish Ministers, statutory and non-statutory stakeholders with adequate information to determine the LSE1 of the Array on the receiving environment. This is further outlined in volume 1, chapter 1.
5. The purpose of this offshore ornithology Array EIA Report chapter is to:

• present the existing environmental baseline established from desk studies, site-specific surveys, numerical modelling studies and consultation with stakeholders;
• identify any assumptions and limitations encountered in compiling the environmental information;
• present the environmental impacts on offshore ornithology arising from the Array and reach a conclusion on the LSE1 on offshore ornithology, based on the information gathered and the analysis and assessments undertaken; and
• highlight any necessary monitoring and/or mitigation measures which are recommended to prevent, reduce or offset the likely significant adverse effects of the Array on offshore ornithology.

11.3.   Study Area

11.3. Study Area

6. Figure 11.1   Open ▸ illustrates the offshore ornithology study area for the Array which encompasses:

• the Array (i.e. the area in which the wind turbines will be located);
• a 4 km buffer around the Array (the Array Offshore Ornithology Study Area); and
• an 8 km buffer around the Array (the Array Offshore Ornithology Survey Area).

7. In addition, it is important to consider that ornithological receptors are highly mobile, travelling potentially long distances whilst foraging and on migration. As such, the Array has the potential to impact seabird populations over a much wider region. Consideration has therefore also been given to regional populations of seabirds that may have connectivity to the Array. The geographic spread of these regional populations varies according to biological connectivity, which differs between species and seasons, as detailed in volume 3, appendix 11.1. The regional Zone of Influence (ZoI) is therefore not a single, defined area, but a dynamic area over which the Array’s impacts may be felt according to the species and time of year.
8. In the breeding season, the regional ZoI is defined as the area within the site- and species-specific foraging range recommended by NatureScot (2023c). For most species, this is the species’ mean-max + 1SD foraging range from Woodward et al. (2019), but in other cases the recommended foraging range is modified to take into account site-specific evidence.
9. Outside of the breeding season, for most species the regional ZoI is defined as the season- and species-specific BDMPS region as described in Furness (2015). However, in line with NatureScot (2023d), a different ZoI is applied to guillemot and large gulls (herring gull, lesser black-backed gull and greater black-backed gull). For those species, the ZoI is defined as the same region as per the breeding season, on the basis of tracking data that indicates birds remain within the general vicinity of their breeding colonies. It should however be noted that the population present within the ZoI may differ between seasons (even if the ZoI itself is the same) as the result of different population structures (i.e. during the breeding season, prior to fledging juvenile chicks will not be present at sea) and the potential for an influx of birds breeding elsewhere.

Figure 11.1: Offshore Ornithology Study Areas

11.4.   Policy and Legislative Context

11.4. Policy and Legislative Context

10. Volume 1, chapter 2 of the Array EIA Report presents the policy and legislation of relevance to renewable energy infrastructure. Policy specifically in relation to offshore ornithology is contained in the Sectoral Marine Plan (SMP) for Offshore Wind Energy (Scottish Government, 2020), the Scottish National Marine Plan (NMP) (Scottish Government, 2015) and the United Kingdom (UK) Marine Policy Statement (MPS) (HM Government, 2011). Table 11.1   Open ▸ presents a summary of the legislative provisions relevant to offshore ornithology, with relevant policy provisions set out in Table 11.2   Open ▸ and Table 11.3   Open ▸ . Further detail is presented in volume 1, chapter 2.

Table 11.1: Summary of Legislation Relevant to Offshore Ornithology

Table 11.2: Summary of Policy Provisions Relevant to Offshore Ornithology

11.5.   Consultation

11.5. Consultation

11. Table 11.3   Open ▸ presents a summary of the key issues raised during consultation activities undertaken to date specific to offshore ornithology for the Array and in the Ossian Array Scoping Opinion (MD-LOT, 2023) along with how these have these have been considered in the development of this offshore ornithology Array EIA Report chapter. Further detail is presented within volume 1, chapter 5. Note that consultation activities/topics that related solely to HRA matters are presented in the Array RIAA (Ossian OWFL, 2024).

Table 11.3: Summary of Issues Raised During Consultation and Scoping Opinion Representations Relevant to Offshore Ornithology

11.6.   Methodology to Inform Baseline

11.6. Methodology to Inform Baseline

12. Information on offshore ornithology has been reviewed and analysed to inform this offshore ornithology baseline. In addition, consultation has been carried out to aid the collection of baseline information.

11.6.1.    Desktop Study

11.6.1. Desktop Study

13. Information on offshore ornithology within the offshore ornithology study area and ZoI was collected through a detailed desktop review of existing studies and datasets which are summarised in Table 11.4   Open ▸ .
14. Both the literature review of the reports and numerical modelling using the datasets were used to characterise the baseline. The offshore ornithology technical report (volume 3, appendix 11.1) includes full details of the analysis undertaken to develop the offshore ornithology baseline.

Table 11.4: Summary of Key Desktop Reports

11.6.2.    Identification of Designated Sites

11.6.2. Identification of Designated Sites

15. All designated sites within the offshore ornithology study area and ZoI that could be affected by the construction, operation and maintenance, and decommissioning phases of the Array were identified. The criteria for identification are described below:

• all designated sites of international, national, and local importance that directly overlap with the offshore ornithology study area or have connectivity/are within the offshore ornithology ZoI (as set out in section 11.3) were identified using a number of sources (including the JNCC’s online resource on the SPAs network, the Ramsar Sites Information Service, and NatureScot’s SiteLink page);
• connectivity was established during the breeding season if a site (for which a species is a qualifying feature) is within foraging range of the Array (using species specific mean maximum foraging range + 1 SD (Woodward et al., 2019) as recommended by NatureScot (2023d)).
• impacts are greatest on the sites with connectivity during the breeding season and therefore for the purpose of this report, only sites with connectivity during the breeding season are considered. During the non-breeding season, species are not as spatially constrained as in the breeding season and can therefore exploit much larger areas (Furness, 2015); and
• where a site has multiple designations, to avoid repetition only the highest designation is listed.

11.6.3.    Site-Specific Surveys

11.6.3. Site-Specific Surveys

16. Site-specific surveys were undertaken, as agreed with NatureScot (refer to Table 11.3   Open ▸ for further details), to inform this offshore ornithology EIA Report chapter for the Array. A summary of the surveys undertaken used to inform the offshore ornithology assessment of effects is outlined in Table 11.5   Open ▸ .

Table 11.5: Summary of Site-Specific Survey Data

11.7.   Baseline Environment

11.7. Baseline Environment

11.7.1.    Overview of Baseline Environment

11.7.1. Overview of Baseline Environment

17. The following sections provide a summary of the offshore ornithology baseline environment. The offshore ornithology technical report, volume 3, appendix 11.1, includes full details of the analysis undertaken to develop the offshore ornithology baseline.

11.7.2.    Designated Sites

11.7.2. Designated Sites

18. Designated sites and relevant qualifying interest features identified for this offshore ornithology Array EIA Report chapter are described in Table 11.6   Open ▸ and presented in Figure 11.2   Open ▸ ( Figure 11.3   Open ▸ for zoomed in illustration). As set out in paragraph 15, the foraging ranges of the qualifying features determined the sites that were identified. Species listed include those named as main components of an assemblage feature, as well as individual qualifying features. Species listed are limited to those identified as VORs in volume 3, appendix 11.1. Within this Array EIA Report chapter, assessment is carried out for VORs in line with the methodology set out in section 11.9. An assessment of the impact of the Array on other designated features and the conservation objectives of protected sites it carried out in the Array RIAA (Ossian OWFL, 2024).
19. Where locally designated sites and national designations (other than European sites) fall within the boundaries of a European site (e.g. SSSIs which have not been assessed within the Array RIAA) and where qualifying interest features are the same, only the European site has been taken forward for assessment. Potential impacts on the integrity and conservation status of the offshore ornithology features of a locally or nationally designated site are assumed to be inherent within the assessment of the European site, so a separate assessment for the local or national site has not been undertaken.
20. It should be noted that distances given in Table 11.6   Open ▸ are measured as the shortest distance between the edge of the Array and the designated site boundary. The distance may therefore differ from measurements calculated using a different approach. In particular, for the apportionment of impacts to breeding colonies carried out as part of the Array RIAA (Ossian OWFL, 2024), following the relevant guidance (NatureScot, 2018), distances are measured from the geometric centre of the Array to the centre of the specific breeding colony location.

Table 11.6: Designated Sites and Relevant Qualifying Interest Features for the Offshore Ornithology Array EIA Report Chapter

Figure 11.2: Offshore Ornithology Designated Sites

Figure 11.3: Offshore Ornithology Designated Sites (zoomed in)

11.7.3.    Important Ecological Features

11.7.3. Important Ecological Features

21. With regards to offshore ornithology, the important ecological features are VORs. VORs have been selected based on the conservation status of the ornithological receptor, their vulnerability to impact (for each impact which has been scoped in for the assessment) and known abundance from site-specific surveys and desktop studies. This is further detailed in volume 3, appendix 11.1.
22. Table 11.7   Open ▸ lists all of the VORs identified for offshore ornithology and their population importance (as set out in volume 3, appendix 11.1).
23. The approach to seasonal definitions and regional populations is further detailed in volume 3, appendix 11.1 but for clarity, the defined seasons and population sizes are included in this report in Table 11.8   Open ▸ and Table 11.9   Open ▸ .
24. The impact of additional mortality due to offshore wind farm effects is assessed in terms of the change in the baseline mortality rate. As detailed within volume 3, appendix 11.1, it has been assumed that all age classes are equally at risk of effects, with each age class affected in proportion to its presence in the population. The average mortality rates used within the assessment are provided in Table 11.10   Open ▸ .

Table 11.7: Offshore Ornithology VORs[3]

Table 11.8: Seasonal Definitions for Species Considered in this Report[4]

Table 11.9: Regional Population Sizes for Species Included in this Report (All Population Estimates are for Individual Birds)[6].

Table 11.10: Demographic rates for key species. Derived from Horswill & Robinson (2015)[8]

11.7.5.    Future Baseline Scenario

11.7.5. Future Baseline Scenario

25. The EIA Regulations require that “a description of the relevant aspects of the current state of the environment (the “baseline scenario”) and an outline of the likely evolution thereof without implementation of the project as far as natural changes from the baseline scenario can be assessed with reasonable effort, on the basis of the availability of environmental information and scientific knowledge” is included within the Array EIA Report.
26. If the Array does not come forward, the ‘without development’ future baseline conditions are described within this section.
27. The UK holds internationally important populations of seabirds (Mitchell et al., 2004). UK seabird populations have shown a marked decline over the last two decades (JNCC, 2020; Mitchell et al., 2020), with over a third of species experiencing declines in breeding abundance of up to 30% or more since the early 1990s (Mitchell et al., 2020; Burnell et al., 2023).
28. A recent study suggests that in terms of number of species affected and the average impact, the three key threats to seabird populations globally are invasive species (165 species affected, across all the most threatened groups), bycatch in fisheries (100 species affected, but with the greatest average impact) and climate change (96 species affected) (Dias et al., 2019; Mitchell et al., 2020).
29. Most seabird species in the UK are at the southern limit of their range in the north-east Atlantic and therefore an increase in global temperatures could result in a northward shift in species’ range with the potential for overall declines in population size (Frederiksen et al., 2007, 2013 and Mitchell et al., 2020). In the UK and Ireland, climate change is considered to be the likely primary cause of decline in seabird populations in the future, with anticipated depletion of breeding conditions for most species either indirectly, through changes in prey abundance, or directly during extreme weather events (Mitchell et al., 2020).
30. Fisheries management will also likely impact on future seabird populations in the UK and Ireland. For many years, seabird species have benefitted from fisheries discards; for scavenging species such as herring gull, kittiwake, great skua and fulmar, population levels may already be above those that naturally occurring food sources would sustain (Votier et al., 2004 and Frederiksen et al., 2013). However, the introduction between 2015 and 2019 of the Common Fisheries Policy Landings Obligation (‘discard ban’) will likely reduce the discard available and ultimately put more pressure on scavenging species.
31. On the other hand, the UK and Scottish Governments recently announced their intention to close the sandeel fisheries in all Scottish waters and the English North Sea (DEFRA, 2024; Scottish Government, 2024a). The intention of this action is to improve the sandeel population, and therefore also benefit predators including seabirds such as kittiwake, puffin and guillemot which feed upon sandeels. This closure may therefore reduce the pressure on those species.
32. Therefore, without the Array, seabird populations would be expected to continue to follow their current population trends, which in many cases is a continuation of declining populations. Climate change is considered to be the likely primary cause of decline in seabird populations in the future. It is believed that the absence of the Array would further delay the transition of the UK from reliance on fossil fuels and therefore further contribute towards climate change impacts and declining seabird populations.

11.7.6.    Data Limitations and Assumptions

11.7.6. Data Limitations and Assumptions

33. Baseline characterisation of the offshore ornithology study area and resulting assessments of significance use site-specific data (DAS) conducted over a period of 24 months (March 2021 to February 2023). As sampling is undertaken once a month for a period of 24 months, it may be considered to represent a snapshot of each month. Indeed, seabird numbers may fluctuate both spatially and temporally in response to environmental conditions. However, the sampling regime adopted is identical to other baseline characterisation surveys at offshore wind farms projects which have been previously agreed by SNCBs as suitable for baseline characterisation.
34. The population estimates for seabird SPA colonies used to inform the assessments in sections 11.11 and 11.12 are taken from the most recent colony count data (Seabirds Count; Burnell et al., 2023), which is based on census surveys undertaken between 2015 and 2021.
35. The current H5N1 strain of Highly Pathogenic Avian Influenza (HPAI) was first recorded in the UK in summer 2021 (Falchieri et al. 2022). Although existing systematic reviews indicate that diseases are seldom a key factor leading to the extinction of vertebrates, diseases can cause population crashes, leading to measurable declines in populations (Young and VanderWerf, 2023).
36. Thousands of seabird mortalities attributed to HPAI were reported across the UK in 2022, with minimum losses of almost 20,000 individuals in Scotland alone (NatureScot, 2023l) and by the end of 2022, 17 of the 25 UK breeding seabird species had tested positive for HPAI (APHA, 2023).
37. In response to the outbreak of HPAI, the RSPB established the HPAI Seabird Surveys Project (Tremlett et al., 2024). This involved a mixture of existing planned surveys, additional volunteer-led surveys and RSPB-led surveys of a number of SPA colonies for 14 priority seabird species, and was undertaken between May and July 2023. The survey method followed standard methods outlined in the Seabird Monitoring Handbook (Walsh et al. 1995), enabling comparisons in population changes with the Seabirds Count estimates, which are based on census surveys undertaken between 2015 to 2021 (Burnell et al., 2023).
38. The HPAI surveys were not intended to fully update the Seabirds Count data (for example, there were gaps in coverage of some sites, some counts lacked key information such as survey time, and some survey counts were estimates rather than accurate counts). However, the RSPB HPAI report (Tremlett et al., 2024) is a useful indicator of how certain species are faring in light of the recent HPAI outbreak.
39. The RSPB HPAI report (Tremlett et al., 2024) showed large declines in gannet of 25% across eight SPAs when compared against the Burnell et al. (2023) pre-HPAI baseline, whereas kittiwake increased by 10% across 21 SPAs and guillemot declined by 6% across 21 SPAs. The RSPB HPAI report (Tremlett et al., 2024) concludes that changes in species such as guillemot may be partially due to other factors as they were already in decline, whereas the decline in gannet is almost certainly attributable to HPAI due to the species showing recent population increases.
40. The baseline DAS data was collected between March 2021 and February 2023 and therefore overlaps with the HPAI outbreak. However, the data presented in volume 3, appendix 11.1 does not demonstrate any clear evidence of impact from HPAI when comparing between years.
41. Overall, the impact of the short, medium and long-term effects of the 2022 HPAI outbreak on seabird colony abundance and vital rates (productivity and survival) on UK breeding colonies is unclear. It is also unclear currently how the distribution and abundance of seabirds at sea has been affected as a result of the 2022 HPAI outbreak. The disease has affected over 60 bird species in the UK, including species such as gannet, razorbill, guillemot, puffin, Manx shearwater, fulmar and small and large gull species (Pearce-Higgins et al., 2023). HPAI has affected gannet and great skua colonies profoundly, with both species now facing increased risk of global extinction (Pearce-Higgins et al., 2023) (the UK supports 55.6% of the global gannet population and 60% of the global great skua population; JNCC, 2021).
42. In the absence of updated SNCB guidance, the assessment approach with regards to HPAI aligns as closely as possible to Natural England’s interim guidance that was submitted as part of Natural England’s Representation in response to the Array EIA Scoping Report (Ossian OWFL, 2023), in the Scoping Opinion (MD-LOT, 2023). Therefore, all quantitative assessment has been carried out without any adjustments in respect to HPAI. This reflects an assumption that reductions in population or colony sizes would translate to proportional reductions in at-sea densities and hence predicted mortalities from the Array.

11.8.   Key Parameters for Assessment

11.8. Key Parameters for Assessment

11.8.1.    Maximum Design Scenario

11.8.1. Maximum Design Scenario

43. The Maximum Design Scenarios (MDSs) identified in Table 11.11   Open ▸ are those expected to have the potential to result in the greatest effect on an identified VOR. These scenarios have been selected from the details provided in volume 1, chapter 3 of the Array EIA Report. Effects of greater adverse significance are not predicted to arise should any other development scenario, based on details within the Project Description (volume 1, chapter 3) (e.g. different infrastructure layout) be taken forward in the final design scheme.

.

Table 11.11: Maximum Design Scenario Considered for Each Potential Impact on Offshore Ornithology

11.8.2.    Species Assessed for Each Impact

11.8.2. Species Assessed for Each Impact

44. Table 11.12   Open ▸ sets out the VORs that are considered for each impact being assessed, alongside an explanatory justification when species are ruled out for a particular impact.

Table 11.12: Species Assessed for Each Impact

11.8.3.    Impacts Scoped Out of the Assessment

11.8.3. Impacts Scoped Out of the Assessment

45. The offshore ornithology pre-Scoping workshop (see Table 11.3   Open ▸ ) was used to facilitate stakeholder engagement on topics to be scoped out of the assessment.
46. On the basis of the baseline environment and the Project Description outlined in volume 1, chapter 3 of the Array EIA Report, a number of impacts are proposed to be scoped out of the assessment for offshore ornithology. This was either agreed with key stakeholders through consultation as discussed in volume 1, chapter 5, or otherwise, the impact was proposed to be scoped out in the Array EIA Scoping Report (Ossian OWFL, 2023) and no concerns were raised by key consultees within the Ossian Array Scoping Opinion (MD-LOT, 2023).
47. These impacts are outlined, together with justification for scoping them out, in Table 11.13   Open ▸ .

Table 11.13: Impacts Scoped Out of the Assessment for Offshore Ornithology (Tick Confirms the Impact is Scoped Out)

11.9.   Methodology for Assessment of Effects

11.9. Methodology for Assessment of Effects

11.9.1.    Overview

11.9.1. Overview

48. The offshore ornithology assessment of effects has followed the methodology set out in volume 1, chapter 6 of the Array EIA Report. Specific to the offshore ornithology EIA, the following guidance documents have also been considered:

• NatureScot Marine Ornithology Guidance Notes to support Offshore Wind Applications (NatureScot, 2023a-k):

-        Guidance Note 1: Guidance to support Offshore Wind Applications: Marine Ornithology – Overview (NatureScot, 2023a);

-        Guidance Note 2: Guidance to support Offshore Wind Applications: Advice for Marine Ornithology Baseline Characterisation Surveys and Reporting (NatureScot, 2023b);

-        Guidance Note 3: Guidance to support Offshore Wind applications: Marine Birds – Identifying theoretical connectivity with breeding site Special Protection Areas using breeding season foraging ranges (NatureScot, 2023c);

-        Guidance Note 4: Guidance to Support Offshore Wind Applications: Ornithology – Determining Connectivity of Marine Birds with Marine Special Protection Areas and Breeding Seabirds from Colony SPAs in the Non Breeding Season (NatureScot, 2023d);

-        Guidance Note 5: Guidance to support Offshore Wind Applications: Recommendations for marine bird population estimates (NatureScot, 2023e);

-        Guidance Note 6: Guidance to support Offshore Wind Applications – Marine Ornithology Impact Pathways for Offshore Wind Developments (NatureScot, 2023f);

-        Guidance Note 7: Guidance to support Offshore Wind Applications: Marine Ornithology – Advice for assessing collision risk of marine birds (NatureScot, 2023g);

-        Guidance Note 8: Guidance to support Offshore Wind applications: Marine Ornithology Advice for assessing the distributional responses, displacement and barrier effects of Marine birds (NatureScot, 2023h);

-        Guidance Note 9: Guidance to support Offshore Wind applications: Marine Ornithology Advice for Seasonal Definitions for Birds in the Scottish Marine Environment (NatureScot, 2023i);

-        Guidance Note 10: Guidance to support Offshore Wind applications: Marine Ornithology Advice for apportioning impacts to breeding colonies (NatureScot, 2023j); and

-        Guidance Note 11: Guidance to support Offshore Wind Applications: Marine Ornithology – Recommendations for Seabird Population Viability Analysis (PVA) (NatureScot, 2023k).

• Incorporating data uncertainty when estimating potential vulnerability of Scottish seabirds to marine renewable energy developments (Wade et al., 2016);
• Assessing vulnerability of marine bird populations to offshore wind farms (Furness et al., 2013);
• Scaling possible adverse effects of marine wind farms on seabirds: developing and applying a vulnerability index (Garthe and Hüppop, 2004);
• Joint SNCB Interim Displacement Advice Note: Advice on how to present assessment information on the extent and potential consequences of seabird displacement from Offshore Wind Farm developments (JNCC, 2022);
• Modelling flight heights of marine birds to more accurately assess collision risk with offshore wind turbines (Johnston et al., 2014);
• Using a Collision Risk Model to Assess Bird Collision Risks for Offshore Wind Farms (Band, 2012);
• A Stochastic Collision Risk Model for Seabirds in Flight (McGregor et al., 2018);
• Guidelines for Ecological Impact Assessment in the UK and Ireland (CIEEM, 2022); and
• Developing Guidance on Ornithological Cumulative Impact Assessment for Offshore Wind Farm Developers (King et al., 2009).

49. The methodology has also considered the needs of the relevant policy and legislation, as described in volume 1, chapter 2 of this Array EIA Report, and Table 11.1   Open ▸ and Table 11.2   Open ▸ within this chapter.

11.9.2.    Criteria for Assessment of Effects

11.9.2. Criteria for Assessment of Effects

50. When determining the significance of effects, a two stage process is used which involves defining the magnitude of the potential impacts and the sensitivity of the receptors. This section describes the criteria applied in this chapter to assign values to the magnitude of potential impacts and the sensitivity of the receptors. The terms used to define magnitude and sensitivity are based on those which are described in further detail in volume 1, chapter 6 of the Array EIA Report.
51. The criteria for defining magnitude in this chapter are outlined in Table 11.14   Open ▸ . Each assessment considers the spatial extent, duration, frequency and reversibility of impact when determining magnitude, and these are outlined within the magnitude section of each impact assessment (e.g. a duration of hours or days would be considered for most receptors to be of short-term duration, which is likely to result in a low magnitude of impact). The definitions have been adapted to be suitable for offshore ornithology, following the approach and guidance set out by CIEEM (2022).
52. To aid with categorising the magnitude of impact, a 1% threshold in increase in baseline mortality was utilised, with the level of impact from the offshore wind farm divided by the baseline mortality estimate. Generally, based on findings from population viability analyses for bird species, it would be considered that increases in mortality rates of less than 1% would be undetectable in terms of changes in population size, whereas increases above 1% may produce detectable effects (Natural England, 2022). Note that NatureScot (2023k) guidance states that a 0.02 percentage point change in survival rate is to be used when assessing the impact to SPA populations. As the EIA deals with larger combined populations (that include non-SPA colonies) and not individual SPA populations, the 1% was deemed as the most appropriate approach for the EIA. A 0.02 percentage point change in survival rate threshold has been used within the Array RIAA (Ossian OWFL, 2024).

Table 11.14: Definition of Terms Relating to the Magnitude of an Impact

53. Further information on levels of population importance and conservation value are given in volume 3, appendix 11.1. Criteria used to determine potential for recovery are given in Table 11.15   Open ▸ .

Table 11.15: Definition of Potential for Recovery

54. The criteria for defining sensitivity in this chapter are outlined in Table 11.16   Open ▸ . The definitions have been adapted to be suitable for offshore ornithology, following the approach and guidance set out by CIEEM (2022). The conservation value of ornithological receptors is based on the population from which individuals are predicted to be drawn. This reflects current understanding of the movements of species, with site-based protection (e.g. SPAs) generally limited to specific periods of the year (e.g. the breeding season). Therefore, conservation value can vary through the year depending on the relative sizes of the number of individuals predicted to be at risk of impact and the population from which they are estimated to be drawn. Conservation value therefore corresponds to the degree of connectivity which is predicted between the offshore wind farm site and protected populations.

Table 11.16: Definition of Terms Relating to the Sensitivity of the Receptor

55. The magnitude of the impact and the sensitivity of the receptor are combined when determining the significance of the effect upon offshore ornithology VORs. The particular method employed for this assessment is presented in Table 11.17   Open ▸ .
56. Where a range is suggested for the significance of effect, for example, minor to moderate, it is possible that this may span the significance threshold. The technical specialist’s professional judgement will be applied to determine which outcome defines the most likely effect, whilst taking into account the sensitivity of the receptor and the magnitude of impact. Where professional judgement is applied to quantify final significance from a range, the assessment will set out the factors that result in the final assessment of significance. These factors may include the likelihood that an effect will occur, data certainty and relevant information about the wider environmental context.
57. For the purposes of this assessment:

• A level of residual effect of moderate or more will be considered a ‘significant’ effect in terms of the EIA Regulations; and
• A level of residual effect of minor or less will be considered ‘not significant’ in terms of the EIA Regulations.

58. Effects of moderate significance or above are therefore considered important in the decision-making process, whilst effects of minor significance or less warrant little, if any, weight in the decision-making process.

Table 11.17: Matrix Used for the Assessment of the Significance of the Effect

11.9.3.    Designated Sites

11.9.3. Designated Sites

59. This offshore ornithology Array EIA Report chapter assesses the LSE1 in EIA terms on the qualifying interest feature(s) of Natura 2000 sites (i.e. nature conservation sites in Europe designated under the Habitats or Birds Directives[11]) and sites in the UK that comprise the National Site Network (collectively termed ‘European sites’) as described within section 11.7.2 of this chapter. The Array RIAA (Ossian OWFL, 2024) includes the assessment of the potential impacts on the features of each protected site individually in terms of the Habitats Regulations (Ossian OWFL, 2024).
60. Where locally designated sites and national designations (other than European sites) fall within the boundaries of a European site (e.g. SSSIs which have not been assessed within the Array RIAA) and where qualifying interest features are the same, only the European site has been taken forward for assessment. Potential impacts on the integrity and conservation status of the offshore ornithology features of a locally or nationally designated site are assumed to be inherent within the assessment of the European site, so a separate assessment for the local or national site has not been undertaken.
61. However, assessment of the LSE1 on a local or nationally designated site which falls outside the boundaries of a European site, but within the offshore ornithology study area, has been considered within this chapter. Given ornithological features are highly mobile, birds within the Array’s ZoI (as defined in section 11.3) may by associated with designated sites over a wide area, or they may not be associated with a designated site. An individual bird may be associated with different designated sites at different times of year or across different years. Therefore, unless there is evidence to the contrary, it is assumed that the impact on a designated site is proportional to the impact of the Array on the wider regional population containing that designated site. Such evidence may include tracking data or similar indicating disproportionately high levels of connectivity between a site and the Array. While impacts have been apportioned to non-European sites, these have not been assessed in any great detail as it is not the standard approach to do so. It is assumed the overall EIA-level effect conclusion is also applicable to any such designated site.

11.10.            Measures Adopted as Part of the Array

11.10. Measures Adopted as Part of the Array

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

Table 11.18: Designed In Measures Adopted as Part of the Array

11.11.            Assessment of Significance

11.11. Assessment of Significance

63. The Maximum Design Scenarios (MDSs) identified in Table 11.11   Open ▸ are those expected to have the potential to result in the greatest effect on an identified VOR. These scenarios have been selected from the details provided in volume 1, chapter 3 of the Array EIA Report. Effects of greater adverse significance are not predicted to arise should any other development scenario, based on details within the Project Description (volume 1, chapter 3) (e.g. different infrastructure layout) be taken forward in the final design scheme.
64. Table 11.11   Open ▸ summarises the potential impacts arising from the construction, operation and maintenance and decommissioning phases of the Array, as well as the maximum design scenario against which each impact has been assessed. An assessment of the significance of the effects of the Array on the offshore ornithology VORs caused by each identified impact is given in sections 11.11 to 11.15.

Temporary habitat loss and disturbance

65. There is potential for temporary, direct benthic habitat loss as a result of activities during the construction and decommissioning phases (e.g. seabed preparation, UXO detonation, drilling, and inter-array and interconnector cables installation and removal). These activities have the potential to affect the foraging efficiency of diving birds.
66. In addition to this direct habitat loss, temporary disturbance as the result of activities during the construction and decommissioning phases of an offshore wind farm has the potential to displace seabirds from an area of sea in which the activity is occurring. In relation to offshore wind farm development, displacement is defined as a reduction in the number of seabirds occurring within or immediately adjacent to an offshore wind farm (Furness et al., 2013).
67. Displacement can be considered as indirect habitat loss, as it results in birds unable to utilise the habitat in the area from which they have been displaced. Therefore, the impacts from both direct habitat loss and disturbance have been considered together.
68. The loss of habitat means that displaced birds may move to areas already occupied by other birds and thus may face higher intra- or inter-specific competition due to a higher density of individuals competing for the same resources. Alternatively, displaced birds may be forced to move into areas of lower quality (e.g. areas of lower prey availability) or travel longer distances to reach habitat of a suitable quality. This could therefore affect their demographic fitness (i.e. survival rates and breeding productivity), as well as potentially impacting on other birds in areas that displaced birds move to (for example, by increasing competition for resources).
69. The MDS ( Table 11.11   Open ▸ ) gives the scenario that would lead to the greatest amount of temporary habitat loss and disturbance during the construction and decommissioning phases. The amount of direct habitat loss is small, with a maximum of 5.82% of the Array expected to be impacted. In addition, no significant adverse effects are expected on fish, shellfish or benthic invertebrate populations as a result of construction or decommissioning activities (see volume 2, chapters 8 and 9). Therefore, it is expected that disturbance and subsequent displacement would be the main impact pathway.
70. The displacement assessment for construction is based on a qualitative approach, considering the magnitude of impact and the sensitivity of the receptor. The species considered for temporary habitat and temporary disturbance during construction and decommissioning are kittiwake, guillemot, razorbill, puffin, fulmar and gannet. All other species were excluded on the basis there is no potential for a significant effect as a result of temporary habitat loss and disturbance (volume 3, appendix 11.3).
71. Few studies have directly considered displacement rates during the construction phase of an offshore wind farm. Most studies have compared pre-construction to post-construction. It is expected that the amount of displacement during the construction phase of the Array would be less than that during the operational phase due to there being a smaller footprint whilst the Array is being constructed.

                        Construction phase

                        Magnitude of impact

72. Disturbance and temporary loss of habitat (including habitat becoming temporarily unsuitable due to disturbance) will occur intermittently throughout the construction period. The construction period is expected to take up to eight years, with activities and locations varying within this time.
73. The impact is predicted to be of local spatial extent, intermittent and 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 construction disturbance and temporary loss of habitat impacts will also be of high reversibility. The magnitude is therefore, considered to be negligible For all species being considered for disturbance and temporary loss of habitat impacts (kittiwake, guillemot, razorbill, puffin, fulmar and gannet).

Kittiwake

                        Sensitivity of receptor

74. In terms of behavioural response to offshore vessel traffic and helicopters, kittiwake are considered have a low vulnerability (Wade et al., 2016).
75. 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 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.
76. 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.
77. Kittiwake 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

78. 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.

Guillemot

                        Sensitivity of the receptor

79. Guillemot are considered to be moderately vulnerable to disturbance (Wade et al., 2016). Whilst there is evidence from studies that guillemot respond adversely to vessel traffic (Rojek et al., 2007), behavioural response to underwater and airborne sounds resulting from construction activities are unknown. Although guillemot are likely to respond to visual stimuli during the construction phase, the impacts of disturbance/displacement are short-term and guillemot have the ability to return to the baseline abundance and distribution after construction.
80. Guillemot raise a single chick per year and breed from the age of six onwards, typically living on average for 23 years (Burnell et al., 2023). Guillemot have undergone decreases of approximately 31% in Scotland since the early 2000s. Surveys managed by the RSPB in 2023 have recorded indicative decreases of 6% across a number of sites in Britain in 2023 when compared against a pre-HPAI baseline (Tremlett et al., 2024). Overall, Guillemot is deemed to have low recoverability.
81. Guillemot is a qualifying interest for three 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, guillemot is considered to be of international value.
82. Guillemot is deemed to be of medium vulnerability, low recoverability and international value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

83. 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.

Razorbill

                        Sensitivity of the receptor

84. As with guillemot, razorbill are deemed to be moderately vulnerable to disturbance from vessels and helicopters at offshore wind farms (Wade et al., 2016). Although razorbill are likely to respond to visual stimuli during the construction phase, the impacts of disturbance/displacement are short-term and razorbill have the ability to return to the baseline conditions after construction.
85. Although the species has a low reproductive potential (only laying one egg) and does not breed until four years old (Robinson, 2005), razorbill are deemed to have a medium recoverability given their increasing trend in abundance in the UK (JNCC, 2020).
86. The Array is within the foraging range of razorbill from two SPAs at which the species is a qualifying feature (Fowlsheugh SPA and Troup, Pennan and Lion’s Heads SPA). In addition, there are a number of smaller colonies within foraging range. The numbers of razorbills recorded during baseline surveys of the Array are considered to be of national importance. Therefore, razorbill is considered to be of international conservation value.
87. Razorbill is deemed to be of medium vulnerability, medium recoverability and international value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

88. 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.

Puffin

                        Sensitivity of the receptor

89. Puffin are considered to be moderately vulnerable to disturbance (Wade et al., 2016). Behavioural responses to underwater and airborne sounds resulting from construction activities are unknown. Although puffin are likely to respond to visual stimuli during the construction phase, the impacts of disturbance/displacement are short-term and puffin have the ability to return to the baseline abundance and distribution after construction (MacArthur Green, 2023).
90. 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 recoverability.
91. 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.
92. 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

93. 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.

Fulmar

                        Sensitivity of the receptor

94. In terms of behavioural response to vessel and helicopter traffic, fulmar are considered have a very low vulnerability (Wade et al., 2016).
95. Fulmar 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. Refer to Table 6.26 of volume 3, appendix 11.1 for details of SPAs with connectivity to the Array with regards to fulmar.
96. Fulmar are considered to have very low reproductive potential, due to an average age of recruitment of nine years old and typically laying only a single egg (Robinson, 2005; Horswill and Robinson, 2015). The fulmar population increased by 77% between the 1969 to 1970 and 1985 to 1988 censuses and remained relatively stable until the early 2000s. Numbers have since declined slightly since, but remain above the level in 1969 to 1970 (JNCC, 2022).
97. 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

98. 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.

Gannet

                        Sensitivity of the receptor

99. Gannet are considered to have a very low vulnerability to other sources of disturbance such as vessel and helicopter traffic (Wade et al., 2016), and so gannet are considered to be of very low vulnerability.
100. 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 HPAI 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.
101. 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. Bass Rock, which falls within the Outer Firth of Forth and St Andrews Bay Complex SPA, located 106.4 km south-west of the Array. The species is therefore considered to be of international value. Refer to volume 3, appendix 11.1 (Table 6.30) for details of SPAs with connectivity to the Array with regards to gannet.
102. Gannet 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

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

                        Secondary mitigation and residual effect

104. No offshore ornithology secondary mitigation is considered necessary for any of the ornithological receptors, because the likely effect in the absence of mitigation is not significant in EIA terms.

                        Decommissioning phase

105. The MDS for the decommissioning phase is assumed to be equal or less than the construction phase ( Table 11.11   Open ▸ ). As such, the assessment of the impacts is the same and is not repeated here. Therefore, as concluded in the construction phase, the impact of temporary habitat loss and disturbance in the decommissioning phase is of minor adverse significance, which is not significant in EIA terms.

Indirect Impacts from Construction/Decommissioning Noise

106. Underwater sound produced during construction and decommissioning activities may impact upon the availability of prey items, for example by causing fish and mobile invertebrates to avoid the Array during construction and decommissioning. Underwater sound may also affect the physiology and behaviour of fish and mobile invertebrates. The reduction or disruption of prey availability due to underwater sound may cause reduced energy intake affecting productivity or survival of offshore ornithology receptors.
107. The potential effects on benthic invertebrates, fish and shellfish has been assessed in volume 2, chapters 8 and 9.

                        Construction phase

                        Magnitude of impact

108. A number of potential impacts on benthic subtidal ecology (including benthic invertebrates) 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.
109. With regards to fish and shellfish prey, volume 2, chapter 9 considered the potential impacts of disturbance during construction on marine species (including shellfish), sandeel, herring and diadromous fish. 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.
110. 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. 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

111. None of the VORs considered in this assessment (as set out in Table 11.7   Open ▸ ) are highly specialist, with all VORs I a moderate degree of flexibility in their habitat preferences and prey items (Del Hoyo et al., 1992). As set out in volume 3, appendix 11.1, the VORs listed in Table 11.7   Open ▸ have a moderate or high habitat flexibility as assessed by Wade et al. (2016), with the exception of little tern, which has low flexibility. This moderate or high habitat flexibility equates to a medium or low vulnerability to changes in prey availability (low flexibility equates to high vulnerability).
112. The recoverability of kittiwake, guillemot, razorbill, puffin, fulmar and gannet is shown in Table 11.19   Open ▸ .
113. 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.
114. 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%, resulting in 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.
115. Sandwich tern typically lay two eggs and breed from the age of three onwards, typically living on average for 12 years (Burnell et al., 2023). Sandwich tern have undergone national decreases of approximately 54% since the early 2000s. Surveys managed by the RSPB in 2023 have recorded indicative decreases of 35% across a number of sites in Britain in 2023 when compared against a pre-HPAI baseline (Tremlett et al., 2024). Therefore, overall Sandwich tern is deemed to have low recoverability.
116. Little tern typically lay two to three eggs and breed from the age of three onwards, typically living on average for 12 years (Burnell et al., 2023). Little tern have undergone decreases of approximately 29% in Scotland since the early 2000s. Little tern is considered to have low recoverability.
117. Common tern typically lay two to three eggs and breed from the age of three onwards, typically living on average for 12 years (Burnell et al., 2023). Common tern have undergone a decline of 24% in Scotland since the early 2000s, but an overall increase of approximately 7% across Britain, Ireland, Isle of Man and Channel Islands (Burnell et al., 2023). Surveys managed by the RSPB in 2023 have recorded indicative decreases of 42% across a number of sites in Britain in 2023 when compared against a pre-HPAI baseline (Tremlett et al., 2024). Therefore, overall common tern is deemed to have low recoverability.
118. Arctic tern typically lay one to two eggs and breed from the age of four onwards. Although their average age is unknown, Arctic terns are long-lived and have been known to breed at 30-34 years of age (Burnell et al., 2023). Arctic tern have undergone a decrease of approximately 54% in Scotland since the early 2000s. Surveys managed by the RSPB in 2023 have recorded indicative decreases of 1% across a number of sites in Britain in 2023 when compared against a pre-HPAI baseline (Tremlett et al., 2024). Therefore, overall Arctic tern is considered to have low recoverability.
119. Great skua typically lay two eggs and breed from the age of four onwards. Although their average age is unknown, great skua are long-lived and have been known to reach 38 years of age (Burnell et al., 2023). Great skua have undergone an increase of approximately 14% in Scotland since the early 2000s. However, surveys managed by the RSPB have recorded indicative declines of 76% across a number of 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 significant short-term declines. Overall great skua is currently considered to have low recoverability.
120. European storm petrel lay one egg and breed from the age of four onwards, typically living on average for 12 years (Burnell et al., 2023). Storm petrel have undergone an increase of approximately 48% in Scotland since the early 2000s. Storm petrel is considered to have medium recoverability.
121. Leach’s storm petrel lay one egg and breed from the age of five onwards. Although their average age is unknown, Leach’s storm petrel are long-lived and have been known to reach 36 years of age (Burnell et al., 2023). Leach’s storm petrel have undergone declines of approximately 79% in Scotland since the early 2000s. Leach’s storm petrel is considered to have low recoverability.
122. Manx shearwater lay one egg and breed from the age of five onwards. Manx shearwater are long-lived and have been known to reach over 50 years of age (Burnell et al., 2023). Manx shearwater have undergone increases of approximately 133% in Scotland since the early 2000s. Manx shearwater is considered to have medium recoverability.
123. With the exception of little tern, the VORs are all deemed to be of low to medium vulnerability, low to medium recoverability and national to international value. The sensitivity of these receptors is therefore considered to range between medium to high sensitivity (refer to Table 11.19   Open ▸ ) .
124. Little tern has a high vulnerability to changes in prey availability, has a low recoverability and is of national conservation value. Therefore, little tern has a high sensitivity.

Table 11.19: Sensitivity of Receptors to Indirect Impacts from Construction/Decommissioning Noise

                        Significance of the effect

125. Given a magnitude of impact of negligible adverse significance, and a high sensitivity, the significance of the effect is concluded to be of minor adverse significance for all receptors, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

126. 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

127. 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 indirect impacts from noise in the decommissioning phase is not significant in EIA terms.

Indirect impacts from UXO clearance

128. There is potential for disturbance, auditory injury and/or mortality for sensitive benthic invertebrates, fish and shellfish species as a result of UXO clearance during the construction phase. The reduction or disruption of prey availability due to UXO detonations may cause reduced energy intake affecting productivity or survival of offshore ornithology receptors.

                        Construction phase

                        Magnitude of impact

129. 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.
130. With regards to fish and shellfish prey, volume 2, chapter 9 considered the potential impacts of disturbance during construction on marine species (including shellfish), sandeel, herring and diadromous fish. 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.
131. 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. 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

132. As with indirect impacts from construction/decommissioning noise, sensitivity is determined by vulnerability to changes in prey availability, recoverability of a species and its conservation value. Therefore, the sensitivity of the receptors is as set out in Table 11.19   Open ▸ , with all VORs having a high sensitivity to changes in prey availability.

                        Significance of the effect

133. Given a magnitude of impact of negligible adverse significance, and a high sensitivity, the significance of the effect is concluded to be of minor adverse significance for all receptors, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

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

Disturbance and displacement from the physical presence of wind turbines and maintenance activities

135. Disturbance as the result of the presence of wind turbines and operational activities during the operation and maintenance phase of an offshore wind farm has the potential to displace seabirds from the area of sea in which wind turbines are located or the activity is occurring. In relation to offshore wind farm development, displacement is defined as a reduction in the number of seabirds occurring within or immediately adjacent to an offshore wind farm (Furness et al., 2013).
136. Displacement can be considered indirect habitat loss, as the result is that that birds are unable to utilise the habitat in the area from which they have been displaced. The loss of habitat means birds may move to areas already occupied by other birds and thus face higher intra- or inter-specific competition due to a higher density of individuals competing for the same resource. Alternatively, displaced birds may be forced to move into areas of lower quality (e.g. areas of lower prey availability) or travel longer distances to reach habitat of a suitable quality. This could therefore affect their demographic fitness (i.e. survival rates and breeding productivity), as well as potentially impacting on other birds in areas that displaced birds move to (for example, by increasing competition for resources).
137. Table 11.11   Open ▸ gives the scenario that would lead to the greatest amount of disturbance and displacement during the operation and maintenance phase. This results from the largest Array and the greatest amount of vessel and helicopter activity.
138. The displacement assessment is based on the use of the matrix approach (JNCC et al., 2022), which was agreed as suitable in the post-Scoping consultation (see Table 11.3   Open ▸ ). As sensitivity to displacement differs considerably between seabird species, species were screened and progressed for the matrix approach using ‘Disturbance Sensitivity’ and ‘Habitat Specialisation’ scores from Bradbury et al. (2014) and Wade et al. (2016) as recommended by the Joint SNCB Interim Displacement Advice Note (JNCC et al., 2022). In addition to the species’ sensitivity rating, the importance of a species abundance as recorded during baseline surveys of the Array was considered as to whether species were progressed to the matrix stage (see volume 3, appendix 11.3). The species progressed to the matrix stage were kittiwake, guillemot, razorbill, puffin, fulmar and gannet, and these species are considered in detail in this section. All other species were excluded on the basis there was no potential for a significant effect (volume, 3, appendix 11.3).
139. For each of the species considered (kittiwake, guillemot, razorbill, puffin, fulmar and gannet: as identified in volume 3, appendix 11.3), displacement impacts were quantified for the population within the Array plus 2 km buffer. SNCBs recommend for most species a standard displacement buffer of 2 km with the exception of the species groups of divers as they can be affected at distances over 4 km (Natural England, 2022; JNCC, 2022).
140. Full displacement matrices showing the estimated mortality resulting from 0% to 100% displacement and 0% to 100% mortality of displaced individuals are provided in volume 3, appendix 11.3. Within the displacement matrices, the rates advocated for by NatureScot (2023h) have been utilised and presented alongside an Applicant’s Approach. These rates are discussed within volume 3, appendix 11.3 and within each species’ section below.
141. Where available, abundance estimates based on MRSea modelling have been used, with design-based abundance estimates used otherwise (see volume 3, appendix 11.1 for details on approaches to abundance estimation). Displacement matrices based solely on design-based abundance estimates are also presented in volume 3, appendix 11.3.

                        Evidence used to inform displacement and mortality rates used in Applicant’s Approach

142. There is limited empirical evidence on which mortality rate to use when assessing the impacts of displacement of offshore wind farms. However, the current NatureScot guidance, based on expert opinion, is to consider a mortality rate of up to 5% (NatureScot, 2023h). Van Kooten et al. (2019) studied the effects of displacement of seabirds using energy-budget models for two scenarios using habitat utilisation maps and a fixed 10% mortality rate. The evidence from this study suggests that a 1% mortality rate for displaced birds is more appropriate than the potentially over-precautionary 5% mortality rate.
143. APEM (2022a,b) also considered mortality rates, though fewer studies have attempted to quantify displacement-consequent mortality given the practical and theoretical limitations in doing so. The review concluded that the available evidence is “incompatible” with a 10% mortality rate and the most likely mortality rate is considered to be “negligible or undetectable”. APEM (2022a,b) suggest that a mortality rate of 1% or less would be more consistent with the available evidence and still precautionary. Therefore, the Applicant’s Approach applies a 1% mortality rate, based on this evidence. The mortality rate of 1% follows previous advice from the Marine Scotland on Forth & Tay projects (Marine Scotland, 2017).

                        Puffin, guillemot and razorbill

144. Evidence shows that auk species exhibit a medium level of sensitivity to vessel and helicopter traffic (Garthe and Hüppop, 2004; Furness and Wade, 2012; Bradbury et al., 2014). Furthermore, displacement impacts from post-consent monitoring studies (from 13 different European offshore windfarm sites) have been collated and reviewed by Dierschke et al., (2016), which found auk species to show ‘weak displacement’ overall, but results were highly variable. Similarly, a recent review submitted by Hornsea Four Offshore Wind Farm (APEM, 2022a) summarises all current post consent-monitoring studies undertaken to date within the North Sea and UK Western Waters and provides an extensive study and analysis of the empirical data from offshore wind farms. This review found that auk displacement varies considerably across different sites, with displacement rates ranging from +112% to -75%, with the most common finding being no significant effect.
145. Of projects that have quantified displacement post-construction, the closest to the Array is Beatrice Offshore Wind Farm (191.63 km from the Array), which has found low levels of guillemot displacement (MacArthur Green, 2023) with results suggesting that the area of decreased abundance which overlaps the wind farm is no more than partially related to the wind farm (and only in the pre-post-1 comparison), and is either linked to other changes in the area such as moving prey hotspots, or may simply be due to chance.
146. Furthermore, evidence suggests that although auk species are somewhat sensitive to displacement, the effects are short-term, and studies indicate auk habituation to offshore windfarms. For example, a study at Thanet Offshore Windfarm found auk species became habituated, and the displacement rate of between 75% and 85% in the first year of operations fell to between 31% and 41% within years two and three of operations (Royal Haskoning, 2013). Further evidence is emerging through additional post-construction monitoring of offshore windfarms; for instance, there are reports of auk numbers increasing and observations of foraging behaviour within the offshore wind farm itself (Leopold and Verdaat, 2018). This suggests the displacement rates of auk species within the Array will reduce over time.
147. Based on the review of the relevant literature, a displacement rate of 50% during the operations and maintenance phase of the Array has been deemed appropriate for the auk species (i.e. guillemot, razorbill and puffin) considered in this assessment. This rate is considered to be highly precautionary as a study of offshore wind farms in the German North Sea found reduced displacement rates (~20%) of guillemots during the breeding season compared to the non-breeding season (Peschko et al., 2020). This is of important consideration, as the mean displacement rates derived from the Dierschke et al. (2016) review was primarily from data collected in the non-breeding season. Therefore, by applying a single displacement rate of 50% across all bio-seasons within the Array, this ensures a precautionary rate is used for the assessment. Additionally, the recent study by MacArthur Green (2019 and 2023) highlighted that a displacement rate of 50% was also suitable for puffin and is therefore the displacement rate utilised within the Applicant’s Approach for all auk species.

                        Gannet

148. Evidence suggests that gannet show a low level of sensitivity to ship and helicopter traffic (Garthe and Hüppop, 2004; Furness and Wade, 2012). However, their avoidance rates to offshore wind farms can be high. Natural England recently reviewed nine studies that reported on northern gannet avoidance rates using a variation of survey methods (Pavat et al., 2023). The avoidance rates reported range from 61.7% to 100%. Another review by APEM (2022b) looked at studies across 25 offshore wind farms, over different seasons, and reported displacement rates of 40% to 60% during the breeding season, and 60% to 80% during the non-breeding season. In light of literature, and following guidance from NatureScot (2023h), using a displacement rate of 70% has been deemed appropriate for the Applicant’s Approach.

                        Kittiwake

149. Kittiwake are considered to have a low habitat specialisation score and low sensitivity to displacement (Bradbury et al., 2014; Furness and Wade, 2012; Nature Scot, 2023h).
150. Studies regarding the displacement at Egmond aan Zee Offshore Wind Farm (Leopold et al., 2011), Bligh Bank Offshore Wind Farm and Thorntonbank Offshore Wind Farm (Vanermen, 2013). Horns Rev Offshore Wind Farm, Princess Amalia Windpark (Furness, 2013) reported no significant displacement of kittiwake.
151. Nature Scot advise a 30% displacement for kittiwake in both the breeding and non-breeding season (Nature Scot, 2023h). In light of this guidance and additional evidence stated, for the purpose of this assessment, precautionary rates of 30% for displacement have been used for the operations and maintenance phase of the Array as part of the Applicant’s Approach.

                        Fulmar

152. Fulmar are considered to have a very low sensitivity to displacement (Bradbury et al. 2014). However Wade et al. (2016) states that the uncertainty surrounding this classification is very high, indicating that evidence around displacement impacts on fulmar are not well understood.
153. Dierschke et al. (2016) classified fulmars as weakly avoiding offshore wind farms, based on post-construction studies at 20 sites, however the authors note that data for this species are limited and fulmar may actually display stronger avoidance behaviour. It is possible that the lack of fishing vessels within wind farm areas makes them unattractive to fulmars (Neumann et al., 2013; Braasch et al., 2015). The study conducted at BARD Offshore Wind Farm showed that some displacement of fulmar occurred, with higher densities observed outside the wind farm area (Braasch et al., 2015), indicating that small scale displacement may be present. Vanermen et al. (2019) stated that no significant displacement results were found for fulmar at Thorntonbank Offshore Wind farm, with Furness (2013) indicating that it is very unlikely that fulmar would be affected by displacement.
154. NatureScot (2023h) do not provide recommended displacement rates for this species and so as a precaution, the Applicant utilised a wide range of displacement rates of 0 to 50% as part of their Applicant’s Approach. Fulmar was assessed as a precaution due to the large scale of uncertainty surrounding fulmar displacement. However, based on expert judgement and the fact that several post-construction monitoring studies have concluded little to no effect, focus has been placed on the 30% displacement rate. This rate was also utilised within the Pentland Floating Offshore Wind Farm Application (HiDef, 2022) as it was deemed the most appropriate rate for fulmar.

                        Operation and maintenance phase

Kittiwake

                        Magnitude of impact

155. 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 11.20   Open ▸ ).
156. In all seasons and on an annual basis, even when using the NatureScot displacement and mortality rates, the predicted increase in the baseline mortality rate does not surpass the 1% threshold. The impact in each season using the NatureScot Approach is predicted to be below 0.07% increase in baseline mortality, and on an annual basis a maximum of 0.03% increase in baseline mortality ( Table 11.20   Open ▸ ).
157. Using the Applicant’s Approach rates, the increase in baseline mortality is expected to be well below a 0.1% increase in baseline mortality in each season. On an annual basis, an annual increase of 0.011% estimated ( Table 11.20   Open ▸ ).
158. The impact is predicted to be of local spatial extent. The impact is expected to occur for the lifespan of the project and therefore be long term, although it is reversible following decommissioning of the Array. It is predicted that the impact will affect the receptor directly. However, even considering the NatureScot Approach, 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 11.20: Kittiwake Seasonal and Annual Displacement Estimates for the Array Plus 2 km Buffer During Operation and Maintenance

                        Sensitivity of the receptor

159. In terms of behavioural response to offshore wind farm structures, kittiwake are considered to be of low vulnerability, with a score of two (out of five) assigned by Wade et al. (2016).
160. 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 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.
161. 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.
162. Kittiwake 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

163. 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

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

Guillemot

                        Magnitude of impact

165. 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 11.21   Open ▸ ).
166. When using the displacement and mortality rates recommended by NatureScot, (2023h) the predicted number of mortalities is 490 to 817 in the breeding season, and 290 to 870 in the non-breeding season. This is an increase in the baseline mortality rate of 0.40% to 0.67% in the breeding season, and 0.14% to 0.41% in the non-breeding season. On an annual basis, the number of mortalities is 780 to 1,687, which is an increase in baseline mortality rates of 0.36% to 0.79% ( Table 11.21   Open ▸ ).
167. Using the Applicant’s Approach of 50% displacement and 1% mortality (in all seasons) the number of mortalities is 136 in the breeding season and 242 in the non-breeding season. This is an increase in the baseline mortality rate of 0.11% in the breeding season, and 0.11% in the non-breeding season. On an annual basis, the number of mortalities is 378, which is an increase in baseline mortality rates of 0.18% ( Table 11.21   Open ▸ ).
168. 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.
169. The impact is predicted to be of local spatial extent. The impact is expected to occur for the lifespan of the Array, although is reversible following decommissioning of the Array 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 low.

Table 11.21: Guillemot Seasonal and Annual Displacement Estimates for the Array Plus 2 km Buffer During Operation

                        Sensitivity of the receptor

170. Guillemot is considered to have a high vulnerability to displacement from offshore wind farm structures, being assigned a score of 4 (out of 5) by Wade et al. (2016).
171. Guillemot raise a single chick per year and breed from the age of six onwards, typically living on average for 23 years (Burnell et al., 2023). Guillemot have undergone decreases of approximately 31% in Scotland since the early 2000s. Surveys managed by the RSPB in 2023 have recorded indicative decreases of 6% across a number of sites in Britain in 2023 when compared against a pre-HPAI baseline (Tremlett et al., 2024). Overall, guillemot is deemed to have low recoverability. The Array is not within the foraging range of guillemot from any SPAs at which the species is a qualifying feature. Based on the regional importance of the population recorded during baseline surveys of the Array guillemot is considered to be of international value.
172. Guillemot 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

173. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor to moderate adverse significance. However, as the predicted impact did not surpass 1% in increased mortality, the overall impact is categorised as having a minor adverse significance, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

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

Razorbill

                        Magnitude of impact

175. 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 11.22   Open ▸ ).
176. When using the displacement and mortality rates recommended by NatureScot,(2023h) the predicted number of mortalities is one to four in the pre-breeding season, 47 to 78 in the breeding season, nine to 27 in the post-breeding season, and one to two in the non-breeding season. This is an increase in the baseline mortality rate of 0.001% to 0.004% in the pre-breeding season, 0.50% to 0.83% in the breeding season, 0.01% to 0.03% in the post-breeding season, and 0.003% to 0.01% in the non-breeding season. On an annual basis, the number of mortalities is 58 to 111, which is an increase in baseline mortality rates of 0.06% to 0.11% ( Table 11.22   Open ▸ ).
177. Using the Applicant’s Approach, the number of mortalities is one in the pre-breeding season, 13 in the breeding season, seven 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 season, 0.14% in the breeding season, 0.01% in the post-breeding season, and 0.003% in the non-breeding season. On an annual basis, the number of mortalities is 22, which is an increase in baseline mortality rates of 0.02% ( Table 11.22   Open ▸ ).
178. 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.
179. 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 Approach rates and the rates recommended by NatureScot (2023h), 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 low.

Table 11.22: Razorbill Seasonal and Annual Displacement Estimates for the Array Plus 2 km Buffer During Operation and Maintenance

                        Sensitivity of the receptor

180. As with guillemot, razorbill are deemed to be highly vulnerable to displacement from offshore wind farms, being assigned a score of 4 (out of 5) by Wade et al. (2016). Although the species has a low reproductive potential (only laying one egg) and does not breed until four years old (Robinson, 2005), razorbill are deemed to have a medium recoverability given their increasing trend in abundance in the UK (JNCC, 2020).
181. The Array is within the foraging range of razorbill from two SPAs at which the species is a qualifying feature (Fowlsheugh SPA and Troup, Pennan and Lion’s Heads SPA). In addition, there are a number of smaller colonies within foraging range. The numbers of razorbills recorded during baseline surveys of the Array are considered to be of national importance. Therefore, razorbill is considered to be of international conservation value.
182. Razorbill is deemed to be of high vulnerability, medium recoverability and international value. The sensitivity of the receptor is therefore, considered to be high.

                        Significance of the effect

183. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor to moderate adverse significance. However, as the predicted impact did not surpass 1% in increased mortality, the overall impact is categorised as having a minor adverse significance, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

184. 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

185. 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 ▸ ).
186. 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 ▸ ).
187. 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 ▸ ).
188. 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.
189. 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