Assessment of Collision Mortality throughout the Year

618. As there are no Arctic tern colonies within mean maximum foraging range (plus 1S.D.) of the Proposed Development array area, there will be no impact from collision on the Arctic tern regional breeding population in the breeding season.
619. As there were very low numbers of predicted Arctic tern collisions for the spring period of the non-breeding season, the totals for the autumn period of the non-breeding season therefore represent the annual collision totals for this species.
620. Using the Developer Approach, the predicted theoretical additional annual mortality due to collision was an estimated eight Arctic terns. This corresponds to an increase in the baseline mortality rate of 0.02% ( Table 11.76   Open ▸ ).
621. Using the Scoping Approach, the predicted theoretical additional annual mortality due to collision was an estimated 14 Arctic terns. This corresponds to an increase in the baseline mortality rate of 0.035% ( Table 11.77   Open ▸ ).
622. The estimated increase in the annual baseline mortality for Arctic tern as a result of collision would result in a very slight decrease in the size of the regional BDMPS population of Arctic tern, in the autumn migration period of the non-breeding season, for both the Developer Approach and the Scoping Approach. The magnitude of this impact is therefore considered to be negligible.

Sensitivity of the Receptor

623. A review of post-construction studies of seabirds at offshore wind farms in European waters concluded that Arctic tern was one of the species that was hardly affected by offshore wind farms or with attraction and avoidance approximately equal over all studies (Dierschke et al., 2016). A review of vulnerability of Scottish seabirds to offshore wind turbines ranked Arctic tern with the 18th highest score in the context of collision impacts, based on flight activity at blade height, manoeuvrability, time spent in flight, nocturnal flight activity and conservation importance (Furness and Wade, 2012). Similarly, Furness et al., (2013) scored Arctic tern as the 17th highest ranked species of concern in the context of collision impacts, while Bradbury et al., (2014), classified the Arctic tern population vulnerability to collision mortality as low.
624. On this basis, Arctic tern sensitivity to collision from operational offshore wind farms is considered to be medium ( Table 11.16   Open ▸ ).
625. In addition, estimated numbers of Arctic terns recorded within the Proposed Development were considered as regionally important in the breeding season (See volume 3, appendix 11.1, annex G), prior to the August influx of birds from SPA and non-SPA breeding colonies from within and outside the region. On this basis the conservation importance for Arctic tern was considered to be low.

Significance of the Effect

626. For collision effects on Arctic tern from the Project alone, for the Developer Approach and the Scoping Approach, 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 negligible to minor adverse significance, which is not significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

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

Great Skua

628. For the Developer Approach, estimated great skua mortality from collision impacts in the Proposed Development array area was based on mean densities of flying birds recorded on baseline digital aerial surveys. For the Scoping Approach, this was based on maximum densities of flying birds recorded on baseline digital aerial surveys.
629. When rounded to the nearest whole bird, the estimated annual number of collisions for great skua were zero for both the Developer Approach and the Scoping Approach ( Table 11.46   Open ▸ ). Total annual estimates for both approaches were very low, at 0.17 birds per year for the Developer Approach, and 0.35 birds per year for the Scoping Approach (volume 3, appendix 11.3. These estimates were made based on the very precautionary avoidance rate of 0.98, therefore actual numbers of collisions are considered to be even lower than these estimates.

Magnitude of Impact

630. The estimated increase in the annual baseline mortality for great skua as a result of collision would result in a very slight decrease in the size of the regional great skua population, for both the Developer Approach and the Scoping Approach. The magnitude of this impact is therefore considered to be negligible.

Assessment of Collision Mortality throughout the Year

631. This level of potential impact is considered to be of negligible magnitude throughout the year, as it represents no discernible increase to baseline mortality levels as a result of collision.

Sensitivity of the Receptor

632. Great skua was not included in a review of post-construction studies of seabirds at offshore wind farms in European waters (Dierschke et al., 2016). However, a review of vulnerability of Scottish seabirds to offshore wind turbines ranked great skua as the ninth highest score in the context of collision impacts, based on flight activity at blade height, manoeuvrability, time spent in flight, nocturnal flight activity and conservation importance (Furness and Wade, 2012), as did a similar review by Furness et al., (2013). Bradbury et al., (2014), classified the great skua population vulnerability to collision mortality as moderate.
633. On this basis, great skua sensitivity to collision from operational offshore wind farms is considered to be medium ( Table 11.16   Open ▸ ).
634. In addition, estimated numbers of great skuas recorded within the Proposed Development were considered to be regionally important in the autumn migration period of the non-breeding season (See volume 3, appendix 11.1, annex G), with individuals likely originating from a number of SPAs and non-SPAs within and outside the region. On this basis the conservation importance for great skua was considered to be low.

Significance of the Effect

635. For collision effects on great skua from the Project alone, for the Developer Approach and the Scoping Approach, 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 negligible to minor adverse significance, which is not significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

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

Collision assessment for migratory species

637. This collision assessment covers migratory water birds and seabirds on passage that were recorded on site-specific baseline surveys. Firstly, a screening exercise was undertaken to review which species to include in the collision assessment ( Table 11.79   Open ▸ ). Some seabird species were screened out on the basis of evidence from previous reviews as to their risk of collision impacts (e.g. Furness and Wade, 2012, Furness et al., 2013 and Bradbury et al., 2014). Other seabird species have already been assessed using CRM. The remaining species that require a collision assessment were assessed using results from the Strategic Assessment of Collision Risk of Scottish Offshore Wind Farms to Migrating Birds (WWT, 2014), as advised in the Scoping Opinion.
638. For the WWT (2014) study, UK seabird and non-seabird species populations potentially at risk from collision with wind turbines at Scottish offshore wind farm sites were shortlisted, proportions of the populations likely to pass the wind farm sites were estimated and CRM was performed. Modelling was carried out for 27 seabird species and 38 non-seabird species. For seabirds, modelling sensitivity analysis was conducted by assuming different migratory corridors and distributions within those corridors and species-specific flying height distributions.
639. It was not possible to use the same approach for non-seabird species, as their migration routes are typically less well known. Instead, migration corridor widths for non-seabird species passing Scottish coastal waters were assumed to comprise the cross-sectional width of the Scottish coast perpendicular to the species flyway or flyways (superimposed as close to the coast as possible). During the CRM the number of individuals of each species estimated to be at risk of collision at each wind farm was calculated as the passage population multiplied by the proportional overlap of each wind farm and that species’ migration corridor width.
640. A number of assumptions were made in the analyses, including on migratory routes and bird distributions within those routes, flight heights and wind turbine avoidance rates (98% was used for all species). In addition, where contemporary population estimates were not available the analyses made use of historic population counts. Collision mortality estimates were assessed in relation to an indicative threshold value of 1% of the passage population. Further details are provided within the Strategic Collision Assessment report (WWT, 2014).

Table 11.79: Type of Collision Assessment undertaken for Bird Species Recorded on Digital Aerial Baseline Surveys in the Offshore Ornithology study area between March 2019 and April 2021.

1 Where the total raw number of a species exceeded 100, the species was considered to occur regularly, denoted by R in table.
2 Based on rankings presented in Furness and Wade (2012), Furness et al., (2013) and Bradbury et al., 2014).
3 Based on sensitivity ranking for similar species great crested grebe.

641. A total of 16 species of seabird and water bird were assessed for collision impacts using the Strategic Collision Assessment report (WWT, 2014) ( Table 11.79   Open ▸ ). These species are discussed below.

Table 11.80: Passage Populations of Seabird Species Recorded in the Offshore Ornithology study area on Baseline Surveys, with Estimated Proportions Passing Along Scottish East Coast, Assigned Coastal Strip and Overall Percent of Species Estimated to fly at Rotor Height

Table 11.81: Passage Populations of Water Bird Species Recorded in the Offshore Ornithology study area on Baseline Surveys, with Estimated Proportions Passing Along Scottish East Coast, Assigned Coastal Strip and Overall Percent of Species Estimated to fly at Rotor Height

642. The WWT (2014) assessment then used the migration extension of the Band (2012) offshore CRM to calculate spring and autumn mortality estimates of seabirds and water birds. For seabird species for which flight height data were available (Cook et al. 2012) all three model options were used. For seabird species lacking flight height data and for non-seabird species only Option 1 was used. An avoidance rate of 98% was assumed for all collision estimates generated during this assessment. Species biometrics used in the collision modelling are detailed in the Strategic Collision Assessment report (WWT, 2014).
643. For seabirds the passage population was adjusted to account for collisions at each wind farm, on the assumption that each wind farm modelled was encountered in order, from north to south in autumn and vice versa in spring. This removed the possibility of individuals being ‘killed’ multiple times. This adjustment used the 98% avoidance rate mortality. No such adjustment was made for non-seabird species, since these birds were modelled as crossing the offshore wind farms on broad fronts which encompassed all the wind farms within their migration corridor. Thus, non-seabird species’ populations were modelled as if each individual was only at risk of encountering one Scottish wind farm.
644. The steps undertaken for estimating collision mortality are summarised below:

• The seasonal (spring/autumn) passage population was proportionately split into east and west components;
• Seabirds: the passage population was multiplied by the proportional overlap between each wind farm in turn and the species’ migration corridor;
• Terrestrial: the passage population was multiplied by the average width of each wind farm divided by the species’ migration front (i.e., to obtain the proportion of the population passing through each wind farm);
• Application of the Band (2012) migrant CRM to the population passing through the wind farm to estimate numbers in collision; and
• Individual wind farm collision estimates summed for each species.
  645. For the seabird species listed in Table 11.80   Open ▸ , a range of collision results are presented based on the different widths of coastal strip and the different flight distributions that were run through the collision model ( Table 11.82   Open ▸ ). Six tables of estimated collision numbers were produced, based on corridor width, corridor distance from shore (near/mid/far) and also uniform or skewed flight distribution within the corridor. Each combination of coastal corridor distance from shore and flight distribution generated different collision estimates due to the variation in the extent of overlap between each corridor and the offshore wind farms. However, the WWT (2014) report concluded that it was not possible to determine which of the alternative scenarios provided the closest representation of migration activity for any given seabird species.

Table 11.82: Estimated Collisions based on Band Option 2, during Spring and Autumn Passage for Populations of Seabird Species Recorded in the Offshore Ornithology study area on Baseline Surveys

1 Based on Band Option 1 due to lack of flight height data.
2 for great black-backed gulls, as Scottish birds are largely sedentary with birds from Norway and further east adding to the non-breeding season population (Forrester et al., 2007), the BDMPS non-breeding season population Furness, 2015) was used, rather than the summed passage population.

646. For the non-seabird species listed in Table 11.81   Open ▸ , the annual migration collision mortality estimates based on an avoidance rate of 98% for all species are presented in Table 11.83   Open ▸ . Following publication of the WWT (2014) report, NatureScot amended the goose avoidance rate to 99.8%, which reduced the values for pink-footed goose by 1/10th. This has been amended in Table 11.83   Open ▸ .

Table 11.83: Estimated Collisions based on Band Option 2 during Spring and Autumn Passage for Populations of Seabird Species Recorded in the Offshore Ornithology study area on Baseline Surveys

1 Based on NatureScot revised avoidance rate of 99.8%.

647. Assuming an indicative threshold value of 1% of the passage population, no non-seabird species had collision mortality estimates (at 98% avoidance) that were of concern ( Table 11.83   Open ▸ ).
648. The only non-seabird species that was recorded in the Offshore Ornithology study area on baseline surveys but is not considered in the WWT (2014) report was lapwing. This species was not included for CRM in the WWT (2014) report due to a lack of data on numbers in Scotland during spring and autumn passage. However, as only one individual was recorded in February 2021, it is considered that numbers of lapwing passing through the Proposed Development array area on spring and autumn passage is likely to be low. Overall, it is considered likely that the population of lapwings which pass through Scottish waters do not appear to be at risk of significant levels of additional mortality due to collisions with Scottish offshore wind farms, for the same reasons as other wader species.
649. The report concluded that at a strategic level the populations of non-seabird species which pass through Scottish waters do not appear to be at risk of significant levels of additional mortality due to collisions with Scottish offshore wind farms. On this basis, it is concluded that there will not be a significant level of additional mortality due to collisions with the Proposed Development array area for the non-seabird species recorded on baseline surveys.

11.11.1.         Proposed Monitoring

650. This section outlines the proposed monitoring proposed for offshore and intertidal ornithology. Proposed monitoring measures are outlined in Table 11.84   Open ▸ below.

Table 11.84: Monitoring Commitments for Offshore and Intertidal Ornithology

11.12. Cumulative Effects Assessment

11.12.1.         Methodology

651. The Cumulative Effects Assessment (CEA) takes into account the impact associated with the Proposed Development together with other relevant plans, projects and activities. Cumulative effects are therefore the combined effect of the Proposed Development in combination with the effects from a number of different projects, on the same receptor or resource. Please see volume 1, chapter 6 for detail on CEA methodology.
652. The projects and plans selected as relevant to the CEA presented within this chapter are based upon the results of a screening exercise (see volume 3, appendix 6.3 of the Offshore EIA Report). Each project or plan has been considered on a case by case basis for screening in or out of this chapter's assessment based upon data confidence, effect-receptor pathways and the spatial/temporal scales involved.
653. In undertaking the CEA for the Proposed Development, it is important to bear in mind that other projects and plans under consideration will have differing potential for proceeding to an operational stage and hence a differing potential to ultimately contribute to a cumulative impact alongside the Proposed Development. Therefore, a tiered approach has been adopted. This provides a framework for placing relative weight upon the potential for each project/plan to be included in the CEA to ultimately be realised, based upon the project/plan’s current stage of maturity and certainty in the projects’ parameters. The tiered approach which has been utilised within the Proposed Development CEA employs the following tiers:

• tier 1 assessment – Proposed Development (Berwick Bank Wind Farm offshore) with Berwick Bank Wind Farm onshore;
• tier 2 assessment – All plans/projects assessed under Tier 1, plus projects which are operational, under construction, those with consent, and those which have been submitted but are not yet determined;
• tier 3 assessment – All plans/projects assessed under Tier 2, plus those projects that have submitted Scoping Report but not a consent application; and
• tier 4 assessment – All plans/projects assessed under Tier 3, plus those projects likely to come forward where an Agreement for Lease (AfL) has been granted.
  654. This tiered approach has been adopted to provide an explicit assessment of the Proposed Development as a whole.
  655. The specific projects scoped into the CEA for offshore and intertidal ornithology, are outlined in Table 11.85   Open ▸ .
  656. The range of potential cumulative impacts is a subset of those considered for the Proposed Development alone assessment. This is because some of the potential impacts identified and assessed for the Proposed Development alone, are localised and temporary in nature. It is considered therefore, that these potential impacts have limited or no potential to interact with similar changes associated with other plans or projects. These have therefore been scoped out of the CEA.
  657. Similarly, some of the potential impacts considered within the Proposed Development alone assessment are specific to a particular phase of development (e.g. construction, operation and maintenance or decommissioning). Where the potential for cumulative effects with other plans or projects only have potential to occur where there is spatial or temporal overlap with the Proposed Development during certain phases of development, impacts associated with a certain phase may be omitted from further consideration where no plans or projects have been identified that have the potential for cumulative effects during this period.
  658. As described in volume 1, chapter 3, the Applicant is developing an additional export cable grid connection to Blyth, Northumberland (the Cambois connection). Therefore, applications for necessary consents (including marine licences) will be applied for separately. The CEA for the Cambois connection is based on information presented in the Cambois Connection Scoping Report (SSER, 2022e), submitted in October 2022. The Cambois connection was considered in the CEA for offshore and intertidal ornithology as the Cambois connection will overlap spatially and temporally with the Proposed Development and the project will engage in activities such as cable burial and installation of cable protection which could potentially impact offshore and intertidal ornithology IEFs. However, based on conclusions on the likely scale of impact from such operations on benthic and fish IEFs (see volume 2, chapters 8 and 9) and limited potential for indirect effects on birds as a result of temporary changes to prey distribution (see paragraph 106 onwards), the potential for cumulative impacts has been screened out ( Table 11.86   Open ▸ ).

Table 11.85: List of Other Projects and Plans Considered Within the CEA for Offshore and Intertidal Ornithology

11.12.2.         Cumulative Effects Assessment

659. An assessment of the likely significance of the cumulative effects of the Proposed Development upon offshore and intertidal ornithology receptors arising from each identified impact is given below.
660. The approach to the CEA was discussed at Ornithology Road Map Meeting 5 (volume 3, appendix 11.8) and was also followed advice presented in the Scoping Opinion.
661. As for the project alone assessment, there were two approaches undertaken for the CEA; the Developer Approach and the Scoping Approach. The reasons for undertaking the Developer Approach in addition to the Scoping Approach are laid out in volume 3, appendix 11.3 and appendix 11.4.

Screening for Cumulative Effects

662. Potential effects arising from the Proposed Development alone have been screened for their potential to create a cumulative impact for ornithological receptors ( Table 11.86   Open ▸ ).

Table 11.86: Potential cumulative effects for ornithological receptors

1 Barrier effect is also included as CEA is based on SNCB Matrix approach (SNCBs, 2017).

Displacement and barrier effects from offshore infrastructure

Tier 1

663. For the cumulative displacement assessment, there are no cumulative displacement impacts for Tier 1.

Tier 2

Construction phase

664. Cumulative effects in the construction phase were scoped out in Table 11.86   Open ▸ and so are not considered further here.

Operation and maintenance phase

Gannet

665. There is potential for both cumulative collision impacts and cumulative displacement effects on gannet. Each of these potential impacts have been assessed separately and then combined to provide an overall cumulative impact. Cumulative collision impacts for gannets are presented in paragraph 870 onwards.
666. The estimated cumulative abundance of gannets from the relevant projects are presented in Table 11.87   Open ▸ . There are a number of projects for which there are no, or limited, data on the number of gannets predicted to be displaced, in particular, for some of the earlier Round 1 and Round 2 developments.
667. The mean maximum foraging range +1 SD for gannet is 315.2±194.2 km. Projects within this foraging range during the breeding period are highlighted in bold in Table 11.87   Open ▸ .

Table 11.87: Cumulative Abundance of Gannets for North Sea offshore wind farm Projects (Projects in bold are within 509.4 km of Proposed Development)

668. The following displacement matrices provide, for the relevant bio-seasons, the estimated cumulative mortality of gannets predicted to occur due to displacement, as determined by the relevant specified rates of displacement and mortality. The approach used for the cumulative displacement assessment follows that of the project alone displacement assessment (see volume 3, appendix 11.4).
669. Each cell presents potential cumulative bird mortality following displacement from the Proposed Development and the other offshore wind farm projects during a bio-season. The outputs highlighted in colour are those based on the displacement and mortality rates used in the Developer Approach (highlighted in orange) and used in the Scoping Approach (highlighted in dark teal). Outputs highlighted in light teal reflect potential uncertainty associated with the selected figures. No adjustments for age classes of birds have been made. Further details are presented in volume 3, appendix 11.4).
670. For the Developer Approach cumulative displacement assessment, a displacement rate of 70% and a mortality rate of 1% was applied to each bio-season based on evaluation of the published literature and in line with values used by other offshore wind farm displacement assessments.
671. For the Scoping Approach cumulative displacement assessment, a displacement rate of 70% and mortality rates of 1% and 3% for the breeding and non-breeding seasons were applied.
672. A complete range of cumulative displacement matrices for the Proposed Development array area and 2 km buffer and other North Sea offshore wind farm projects for the different bio-seasons for both the Developer Approach and the Scoping Approach are presented in Table 11.88   Open ▸ , Table 11.89   Open ▸ and Table 11.90   Open ▸ .

Table 11.88: Potential Cumulative Gannet Mortality following Displacement from Offshore Wind Farms in the Breeding Season

Orange box - Based on 70% displacement rate and 1% mortality rate (Developer Approach and lower range of Scoping Approach).
Dark teal box - Based on 70% displacement rate and 3% mortality rate (upper range of Scoping Approach).

Table 11.89: Potential Cumulative Gannet Mortality following Displacement from Offshore Wind Farms in the Autumn Migration Period of the Non-Breeding Season

Orange box - Based on 70% displacement rate and 1% mortality rate (Developer Approach and lower range of Scoping Approach).
Dark teal box - Based on 70% displacement rate and 3% mortality rate (upper range of Scoping Approach).

Table 11.90: Potential Cumulative Gannet Mortality following Displacement from Offshore Wind Farms in the Spring Migration Period of the Non-Breeding Season

Orange box - Based on 70% displacement rate and 1% mortality rate (Developer Approach and lower range of Scoping Approach).
Dark teal box - Based on 70% displacement rate and 3% mortality rate (upper range of Scoping Approach).

Magnitude of impact

673. For the Developer Approach, annual cumulative estimated gannet mortality from displacement by Tier 2 projects was based on 70% displacement and 1% mortality, which was further broken down into the relevant bio-seasons in Table 11.91   Open ▸ . The overall baseline mortality rates were based on age-specific demographic rates and age class proportions as presented in Table 11.21   Open ▸ . The potential magnitude of impact was estimated by calculating the increase in cumulative baseline mortality within each bio-season with respect to the regional populations.

Table 11.91: Cumulative Displacement Mortality Estimates for Gannet for Tier 2 projects by bio-season for Developer Approach

1 Breeding season assessment is for breeding adults only.
2 Mortality is 1% in breeding and non-breeding season.

Breeding Season

674. During the breeding season, the cumulative abundance for gannet was estimated to be 26,294 individuals. When considering the Developer Approach and Scoping Approach displacement rate of 70% this would affect an estimated 18,406 birds. However, this estimate includes non-breeding adults and immature birds, as well as breeding adults.
675. Studies have shown that for several seabird species, in addition to breeding birds, colonies are also attended by many immature individuals and a smaller number of non-breeding adults (e.g. Wanless et al., 1998). There is little information on the breakdown of immature and non-breeding adults present at a colony, however, for the purposes of this assessment the estimated proportion of immature, non-breeding birds across all wind farms was based on age breakdown calculated for the Berwick Bank PVA study (see volume 3, appendix 11.6). Based on this breakdown, 46.4% of birds present are likely to be immature birds, with 53.6% of birds likely to be adult birds
676. If 53.6% of the population present are adults, then this would mean that an estimated 9,866 gannets displaced from offshore wind farms during the breeding period would be adult birds.
677. Applying the Developer Approach mortality rate of 1%, the predicted theoretical additional mortality due to displacement effects would be 184 gannets (99 adults) in the breeding season. However, a proportion of adult birds present at colonies in the breeding season will opt not to breed in a particular breeding season. It has been estimated that 10% of adult gannets may be “sabbatical” birds in any particular breeding season (volume 3, appendix 11.6), and this has been applied for this assessment. On this basis, ten adult gannets were considered to be not breeding and so 89 adult breeding gannets were taken forward for the breeding season assessment.
678. The total gannet regional baseline breeding population is estimated to be 323,836 individuals. Using the adult baseline mortality rate of 0.046 ( Table 11.21   Open ▸ ), the predicted baseline mortality of gannets is 14,896 adult birds per breeding season. The additional predicted mortality of 89 adult gannets would increase the baseline mortality rate by 0.60% ( Table 11.91   Open ▸ ).
679. For Scoping Approach A, annual cumulative estimated gannet mortality from displacement by Tier 2 projects was based on 70% displacement and 1% mortality in the breeding and non-breeding seasons, which was further broken down into the relevant bio-seasons in Table 11.92   Open ▸ .

Table 11.92: Cumulative Displacement Mortality Estimates for Gannet for Tier 2 projects by bio-season for Scoping Approach A

1 Breeding season assessment is for breeding adults only.
2 Mortality is 1% and 3% in breeding season and 1% and 3% in non-breeding season.

680. If 53.6% of the population present are adults, then this would mean that an estimated 9,866 gannets displaced from offshore wind farms during the breeding period would be adult birds.
681. Applying the Scoping Approach A mortality rate of 1%, the predicted theoretical additional mortality due to cumulative displacement effects would be 184 gannets (99 adults) in the breeding season. Applying the 10% rate for “sabbatical” non-breeding birds, resulted in 89 adult breeding gannets being taken forward for the breeding season assessment.
682. The total gannet regional baseline breeding population is estimated to be 323,836 individuals. Using the adult baseline mortality rate of 0.046 ( Table 11.21   Open ▸ ), the predicted baseline mortality of gannets is 14,896 adult birds per breeding season. The additional predicted mortality of 89 adult gannets would increase the baseline mortality rate by 0.60% ( Table 11.92   Open ▸ ).
683. For Scoping Approach B, annual cumulative estimated gannet mortality from displacement by Tier 2 projects was based on 70% displacement and 3% mortality in the breeding and non-breeding seasons, which was further broken down into the relevant bio-seasons in Table 11.93   Open ▸ .

Table 11.93: Cumulative Displacement Mortality Estimates for Gannet for Tier 2 projects by bio-season for Scoping Approach B

1 Breeding season assessment is for breeding adults only.
2 Mortality is 1% and 3% in breeding season and 1% and 3% in non-breeding season.

684. If 53.6% of the population present are adults, then this would mean that an estimated 9,866 gannets displaced from offshore wind farms during the breeding period would be adult birds.
685. Applying the Scoping Approach B mortality rate of 3%, the predicted theoretical additional mortality due to displacement effects would be 552 gannets (296 adults) in the breeding season. Applying the 10% rate for “sabbatical” non-breeding birds, resulted in 30 birds being considered as non-breeding “sabbatical birds, with 266 adult breeding gannets being taken forward for the breeding season assessment.
686. The total gannet regional baseline breeding population is estimated to be 323,836 individuals. Using the adult baseline mortality rate of 0.046 ( Table 11.21   Open ▸ ), the predicted baseline mortality of gannets is 14,896 adult birds per breeding season. The additional predicted mortality of 266 adult gannets would increase the baseline mortality rate by 1.79% ( Table 11.93   Open ▸ ).

Non-breeding season – Autumn Migration Period

687. For the autumn migration period of the non-breeding season, the cumulative abundance for gannet was 23,536 individuals. When considering the Developer Approach and Scoping Approach displacement rate of 70%, this would affect an estimated 16,475 birds.
688. Based on information presented in Furness (2015), in the non-breeding season 45% of the population present are immature birds and 55% of birds are adults. This would mean that an estimated 7,414 gannets displaced during the autumn migration period would be immature birds, with 9,061 adult birds also displaced.
689. Applying the Developer Approach mortality rate of 1%, the predicted theoretical additional mortality due to displacement effects was 165 gannets in the autumn migration period. Based on Furness (2015), the total gannet BDMPS regional baseline population for the autumn migration period is predicted to be 456,298 individuals. Using the average baseline mortality rate of 0.151 ( Table 11.21   Open ▸ ), the predicted regional baseline mortality of gannets is 68,901 birds in the autumn migration period. The additional predicted mortality of 165 gannets would increase the baseline mortality rate by 0.24% ( Table 11.91   Open ▸ ).
690. Applying the Scoping Approach A mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 165 gannets. This additional predicted mortality would increase the baseline mortality rate by 0.24% ( Table 11.92   Open ▸ ).
691. Applying the Scoping Approach B mortality rate of 3%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 494 gannets. This additional predicted mortality would increase the baseline mortality rate by 0.72% ( Table 11.93   Open ▸ ).

Non-breeding season – Spring Migration Period

692. For the spring migration period of the non-breeding season, the cumulative abundance for gannet was 5,565 individuals. When considering the Developer Approach and Scoping Approach displacement rate of 70%, this would affect an estimated 3,896 birds.
693. Based on information presented in Furness (2015), in the non-breeding season 45% of the population present are immature birds and 55% of birds are adults. This would mean that an estimated 1,753 gannets displaced during the spring migration period would be immature birds, with 2,143 adult birds also displaced.
694. Applying the Developer Approach mortality rate of 1%, the predicted theoretical additional mortality due to displacement effects was 39 gannets in the spring migration period. Based on Furness (2015), the total gannet BDMPS regional baseline population for the spring migration period is predicted to be 248,385 individuals ( Table 11.9   Open ▸ ). Using the average baseline mortality rate of 0.151 ( Table 11.21   Open ▸ ), the predicted regional baseline mortality of gannets is 37,506 birds in the spring migration period. The additional predicted mortality of 39 gannets would increase the baseline mortality rate by 0.10% ( Table 11.91   Open ▸ ).
695. Applying the Scoping Approach A mortality rate of 1%, the predicted theoretical additional mortality due to displacement effects was 39 gannets in the spring migration period. This additional predicted mortality would increase the baseline mortality rate by 0.10% ( Table 11.92   Open ▸ ).
696. Applying the Scoping Approach B mortality rate of 3%, the predicted theoretical additional mortality due to displacement effects was 117 gannets in the spring migration period. This additional predicted mortality would increase the baseline mortality rate by 0.31% ( Table 11.93   Open ▸ ).

Assessment of Displacement Mortality throughout the Year

697. Predicted gannet mortality as a result of cumulative displacement for all seasons as calculated above, was summed for the whole year.
698. Based on an assumed displacement rate of 70% and the Developer Approach mortality rate of 1%, the predicted theoretical annual additional mortality due to cumulative displacement effects was an estimated 293 gannets. This corresponds to an increase in the baseline mortality rate of 0.94% ( Table 11.91   Open ▸ ).
699. Applying the Scoping Approach A displacement rate of 70% and mortality rate of 1%, the predicted theoretical additional annual mortality due to cumulative displacement effects was an estimated 293 gannets. This corresponds to an increase in the baseline mortality rate of 0.94% ( Table 11.92   Open ▸ ).
700. Applying the Scoping Approach B displacement rate of 70% and mortality rate of 3%, the predicted theoretical additional annual mortality due to cumulative displacement effects was an estimated 777 gannets. This corresponds to an increase in the baseline mortality rate of 2.82% ( Table 11.93   Open ▸ ).
701. As these cumulative displacement mortality estimates suggested a potentially significant increase in the cumulative baseline mortality rate for gannet for both the Developer Approach and the Scoping Approaches, cumulative PVA analysis for combined displacement and collision effects was conducted on the gannet regional SPA population. The cumulative PVA assessment for gannet is presented following the cumulative collision impact section of this section, from paragraph 892 onwards.

Kittiwake

702. There is potential for both cumulative collision impacts and cumulative displacement effects on kittiwake. Each of these potential impacts have been assessed separately and then combined to provide an overall cumulative impact.
703. The estimated cumulative abundance of kittiwakes from the relevant projects are presented in Table 11.94   Open ▸ . As displacement effects are not required to be assessed for English projects, there were no mean seasonal peak figures available for any projects outside Scottish waters, therefore the cumulative assessment for kittiwake was limited to Scottish offshore wind farm projects. In addition, complete figures were only available in the breeding season, therefore only cumulative breeding season effects are presented.
704. The mean maximum foraging range +1 SD for kittiwake is 156.1±144.5 km. Scottish projects within this foraging range during the breeding period are highlighted in bold in Table 11.94   Open ▸ .

Table 11.94: Cumulative Abundance of Kittiwakes for North Sea Offshore Wind Farm Projects (Projects in bold are within 300.6 km of Proposed Development)

1 = Development site only (no buffer).
2= Development site plus 1km buffer.
NA = Not available.

705. The following displacement matrices provide the estimated cumulative mortality of kittiwakes predicted to occur due to displacement, as determined by the relevant specified rates of displacement and mortality. The approach used for the cumulative displacement assessment follows that of the project alone displacement assessment (see volume 3, appendix 11.4).
706. Each cell presents potential cumulative bird mortality following displacement from the Proposed Development and the other offshore wind farm projects in the breeding season. The outputs highlighted in colour are those based on the displacement and mortality rates used in the Developer Approach (highlighted in orange) and used in the Scoping Approach (highlighted in dark teal). Outputs highlighted in light teal reflect potential uncertainty associated with the selected figures. No adjustments for age classes of birds have been made in the matrices. Further details are presented in volume 3, appendix 11.4).
707. For the Developer Approach cumulative displacement assessment, a displacement rate of 30% and a mortality rate of 2% was applied to the breeding season based on evaluation of the published literature and in line with values used by other offshore wind farm displacement assessments. No cumulative displacement assessment was undertaken for the non-breeding season.
708. For the cumulative displacement assessment for Scoping Approach A, a displacement rate of 30% and a mortality rate of 1% for the breeding and non-breeding seasons was applied. However, cumulative abundance figures for the non-breeding season for kittiwakes were not available for some of the older projects.
709. For the cumulative displacement assessment for Scoping Approach B, a displacement rate of 30% and a mortality rate of 3% for the breeding and non-breeding seasons was applied.
710. A complete range of cumulative displacement matrices for the Proposed Development array area and 2 km buffer and other North Sea offshore wind farm projects for the different bio-seasons for both the Developer Approach and Scoping Approaches A and B are presented in Table 11.95   Open ▸ , Table 11.96   Open ▸ and Table 11.97   Open ▸ .

Table 11.95: Potential Cumulative Kittiwake Mortality following Displacement from Offshore Wind Farms in the Breeding Season

Orange box - Based on 30% displacement rate and 2% mortality rate (Developer Approach).
Dark teal box - Based on 30% displacement rate and 1% mortality rates (Scoping Approach A).
Dark teal box - Based on 30% displacement rate and 3% mortality rates (Scoping Approach B).

Table 11.96: Potential Cumulative Kittiwake Mortality following Displacement from Offshore Wind Farms in the Autumn Period of the Non-breeding Season (Scoping Approach A & B only)

Dark teal box - Based on 30% displacement rate and 1% mortality rates (Scoping Approach A).
Dark teal box - Based on 30% displacement rate and 3% mortality rates (Scoping Approach B).

Table 11.97   Open ▸ : Potential Cumulative Kittiwake Mortality following Displacement from Offshore Wind Farms in the Spring Period of the Non-breeding Season (Scoping Approach A & B only)

Dark teal box - Based on 30% displacement rate and 1% mortality rates (Scoping Approach A).
Dark teal box - Based on 30% displacement rate and 3% mortality rates (Scoping Approach B).

Magnitude of impact

711. For the Developer Approach, annual cumulative estimated kittiwake mortality from displacement by Tier 2 projects was based on 30% displacement and 2% mortality, for the breeding season only ( Table 11.98   Open ▸ ). The overall baseline mortality rates were based on age-specific demographic rates and age class proportions as presented in Table 11.21   Open ▸ . The potential magnitude of impact was estimated by calculating the increase in cumulative baseline mortality within each bio-season with respect to the regional populations.

Table 11.98: Cumulative Displacement Mortality Estimates for Kittiwake for Tier 2 projects in Breeding Season, for Developer Approach

1 Breeding season assessment is for breeding adults only.
2 Mortality is 2% in breeding season only.

Breeding Season

712. During the breeding season, the cumulative abundance for kittiwake was estimated to be 61,447 individuals ( Table 11.94   Open ▸ ). When considering the Developer Approach and Scoping Approach displacement rate of 30% this would affect an estimated 18,434 birds. However, this estimate includes non-breeding adults and immature birds, as well as breeding adults.
713. Studies have shown that for several seabird species, in addition to breeding birds, colonies are also attended by many immature individuals and a smaller number of non-breeding adults (e.g. Wanless et al., 1998). There is little information on the breakdown of immature and non-breeding adults present at a colony, however, for the purposes of this assessment the estimated proportion of immature, non-breeding birds across all wind farms was based on age breakdown calculated for the Berwick Bank PVA study (see volume 3, appendix 11.6). Based on this breakdown, 46% of birds present are likely to be immature birds, with 54% of birds likely to be adult birds
714. If 54% of the population present are adults, then this would mean that an estimated 9,954 kittiwakes displaced from offshore wind farms during the breeding period would be adult birds.
715. Applying the Developer Approach mortality rate of 2%, the predicted theoretical additional mortality due to displacement effects would be 369 kittiwakes (199 adults) in the breeding season. However, a proportion of adult birds present at colonies in the breeding season will opt not to breed in a particular breeding season. It has been estimated that 10% of adult kittiwakes may be “sabbatical” birds in any particular breeding season (volume 3, appendix 11.6), and this has been applied for this assessment. On this basis, 20 adult kittiwakes were considered to be not breeding and so 179 adult breeding kittiwakes were taken forward for the breeding season assessment.
716. The total kittiwake regional baseline breeding population is estimated to be 319,126 individuals ( Table 11.9   Open ▸ ). Using the adult baseline mortality rate of 0.145 ( Table 11.21   Open ▸ ), the predicted baseline mortality of kittiwakes is 46,273 adult birds per breeding season. The additional predicted mortality of 179 adult kittiwakes would increase the baseline mortality rate by 0.39% ( Table 11.98   Open ▸ ).
717. For Scoping Approach A, annual cumulative estimated kittiwake mortality from displacement by Tier 2 projects was based on 30% displacement and 1% mortality in the breeding season, ( Table 11.99   Open ▸ ).

Table 11.99: Cumulative Displacement Mortality Estimates for Kittiwake for Tier 2 projects in Breeding Season for Scoping Approach A

1 Breeding season assessment is for breeding adults only.
2 Mortality is 1% in the breeding and non-breeding seasons.

718. If 54% of the population present are adults, then this would mean that an estimated 9,954 kittiwakes displaced from offshore wind farms during the breeding period would be adult birds.
719. Applying the Scoping Approach A mortality rate of 1%, the predicted theoretical additional mortality due to cumulative displacement effects would be 184 kittiwakes (100 adults) in the breeding season. Applying the 10% rate for “sabbatical” non-breeding birds, resulted in 10 birds being considered as non-breeding “sabbatical birds, with 90 adult breeding kittiwakes being taken forward for the breeding season assessment.
720. The total kittiwake regional baseline breeding population is estimated to be 319,126 individuals. Using the adult baseline mortality rate of 0.145 ( Table 11.21   Open ▸ ), the predicted baseline mortality of kittiwakes is 46,273 adult birds per breeding season. The additional predicted mortality of 90 adult kittiwakes would increase the baseline mortality rate by 0.19% ( Table 11.99   Open ▸ ).
721. For Scoping Approach B, annual cumulative estimated kittiwake mortality from displacement by Tier 2 projects was based on 30% displacement and 3% mortality in the breeding season ( Table 11.100   Open ▸ ).

Table 11.100: Cumulative Displacement Mortality Estimates for Kittiwake for Tier 1 and 2 projects in Breeding Season for Scoping Approach B

1 Breeding season assessment is for breeding adults only.
2 Mortality is 3% in the breeding and non-breeding seasons.

722. If 54% of the population present are adults, then this would mean that an estimated 9,954 kittiwakes displaced from offshore wind farms during the breeding period would be adult birds.
723. Applying the Scoping Approach B mortality rate of 3%, the predicted theoretical additional mortality due to cumulative displacement effects would be 553 kittiwakes (299 adults) in the breeding season. Applying the 10% rate for “sabbatical” non-breeding birds, resulted in 30 birds being considered as non-breeding “sabbatical birds, with 269 adult breeding kittiwakes being taken forward for the breeding season assessment.
724. The total kittiwake regional baseline breeding population is estimated to be 319,126 individuals. Using the adult baseline mortality rate of 0.145 ( Table 11.21   Open ▸ ), the predicted baseline mortality of kittiwakes is 46,273 adult birds per breeding season. The additional predicted mortality of 269 adult kittiwakes would increase the baseline mortality rate by 0.58% ( Table 11.100   Open ▸ ).