4.9. Great skua

93. Collisions of great skua estimated by the Band method were close to zero in all of the scenarios for both the Developer and Scoping Approaches, therefore, further breakdowns beyond those given in Table 4.31 and Table 4.32 are not presented.

Table 4.31:  Summary of estimated number of annual collisions for great skua for the five wind turbine generator sizes from the Band model Options 2 and 3 using the Developer Approach and generic flight height data, for turbine Type A (wide chord and slow rotational speed) and B (narrow chord and fast rotational speed). Avoidance rates are from SNCBs (2014).

Table 4.32:  Summary of estimated number of annual collisions for great skua for the five wind turbine generator sizes from the Band model Options 2 and 3 using the Scoping Approach and generic flight height data, for turbine Type A (wide chord and slow rotational speed) and B (narrow chord and fast rotational speed). Avoidance rates are from SNCBs (2014).

5.             Conclusion 

5. Conclusion

94. For this report, the worst-case estimated number of annual collisions for each species was identified from the outputs of the deterministic Band (2012) model. The scenarios differed in the rating and type of turbine (based on chord width and rotational speed) and model Option chosen. However, we limited our search for the worst-case to scenarios that used generic flight height data of Johnston et al. (2014a; 2014b) only (i.e. Options 2 and 3) as this has been endorsed by SNCBs (SNCBs, 2014) and advised in the Scoping Opinion (4 February 2022); this represents the Scoping Approach for assessing collision risk for seabird species at the Proposed Development Array.
95. The results show that the worst-case ornithology collision impacts for all species modelled are predicted for the 14MW turbine and hence it is these values that are taken forward into the Population Viability Analysis (Technical Appendix 11.6) and assessed in the Environmental Statement.
96. The worst-case turbine scenario was the same (14 MW) for all species regardless of which avoidance rates or Approach was used. However, for kittiwake and gannet, estimated collisions were considerably lower when using Bowgen & Cook (2018), with a reduction of 9% and 54% respectively, when compared with outputs using SNCBs (2014) avoidance rates for both the Developer and Scoping Approaches.
97. For comparison of the worst-case scenario from the Band (2012) model, the sCRM was also used. Using the Developer Approach (which differs from the Scoping Approach by use of mean monthly densities, rather than monthly maximum densities), the results from the sCRM for kittiwake were considerably lower (-46%). For other species, sCRM estimates were also lower for lesser black-backed gull (-33%) and herring gulls (-58%) unchanged for common tern, and higher for Arctic tern (+43%), little gull (-80%) and great skua (+83%). Similar results were obtained when using the Scoping Approach. The results from the sCRM were lower for kittiwake, herring gull and lesser black-backed gull (-46%, -36%, -33% respectively). For other species, sCRM estimates were unchanged for common tern, and higher for Arctic tern (+36%), little gull (-64%) and great skua (+65%).
98. Due to its stochastic nature, estimates from the sCRM are not directly comparable with Band outputs because the output is a distribution rather than a single estimate of collisions. Recommended avoidance rates also differ between Band and sCRM methods.
99. The estimated annual number of collisions was greatest for kittiwake at 685 birds per annum using the Developer Approach and 986 using the Scoping Approach based on Band model Option 2 and using generic flight height data and SNCBs (214) avoidance rates. Use of site-specific boat-based flight height data resulted in significantly lower annual mortality estimates: based on rangefinder data, the mean estimated annual number of collisions for kittiwake using the Developer and Scoping Approaches were 56 and 81 birds respectively, and visual observer data, the annual mean was 225 and 324 kittiwakes for the Developer and Scoping Approaches respectively.

6.             Summary

6. Summary

100. Berwick Bank Wind Farm Limited (BBWFL) (the ‘Applicant’) is a wholly owned subsidiary of SSE Renewables Limited and is developing the Berwick Bank Wind Farm (the ‘Project’) located at the mouth of the North Sea’s Firth of Forth.
101. Digital aerial surveys were flown March 2019 – April 2021 to provide two years of baseline data collection on the seabirds and other marine megafauna in the Offshore Ornithology Study Area (Array area and a 16km buffer). Monthly estimates of flying birds within the proposed Array area only were used in the CRM reported here.
102. Collision risk estimates are presented for eight species vulnerable to collision at OWFs: kittiwake Rissa tridactyla, herring gull Larus argentatus, lesser black-backed gull Larus fuscus, gannet Morus bassanus, Arctic tern Sterna paradisaea, common tern Sterna hirundo, little gull Hydrocoloeus minutus and great skua Stercorarius skua.
103. Two approaches to CRM have been used:

• Deterministic offshore Band CRM (Band, 2012); and
• sCRM (Masden, 2015; McGregor et al., 2018).

104. The results from the Band CRM will be those relied upon for further analyses (i.e. PVA) given that this Approach utilises endorsed SNCBs avoidance rates. The sCRM approach, which takes account of the uncertainty around input parameters, is used only for comparative purposes of the worst-case.
105. Only Band models 2 (basic) and 3 (extended) were used as they use the generic flight height data of Johnston et al. (2014a; 2014b). The models were parameterised using SNCBs (2014) advised avoidance rates; Bowgen and Cook (2018) avoidance rates; seabird morphometric data from Pennycuick (1997) and Alerstam et al. (2007); nocturnal activity from Garthe and Hüppop (2004), Furness et al. (2018) and the Seagreen EIA Optimised Project Addendum (2018); and flight speed from Pennycuick (1997).
106. The Band models were run for each of the five turbine scenarios. Additionally, scenarios for turbines 18 MW – 24 MW were of two types: Type A (wide chord and slower rotational speed) and Type B (narrower chord and faster rotational speed).
107. Estimates of collisions were calculated for each bio-season based on definitions based on NatureScot, (2020) for the breeding and non-breeding seasons. Non-breeding seasons for kittiwake and gannet were based on the spring and autumn migration periods defined by the BDMPS of Furness (2015).
108. Following the release of the Scoping Opinion and associated Consultee representations and advice, the Applicant determined to undertake a “dual assessment” of the collision risk posed by the Project:

• Scoping Approach: monthly maximum density of relevant seabird species within the Development Array area are to be used in the CRMs based on NatureScot and MSS recommendation; and
• Developer Approach: monthly mean density of relevant seabird species within the Development Array area are to be used in the CRMs based on the Applicant opinion.

109. The 14 MW turbine size resulted in the worst-case ornithology collision impacts across all species and hence it is these values that are taken forward into the PVA and assessed in the Environmental Statement. The estimated number of collisions per annum using the deterministic Band model was highest for kittiwake (685 birds for the Developer Approach and 986 birds for the Scoping Approach). Estimates were shown to be sensitive to the source of flight height data used in the Band model. Based on site-specific rangefinder data, the mean estimated annual number of collisions for kittiwake using the Developer and Scoping Approaches were 56 and 81 birds respectively. Using the visual observer collected site- data, the annual mean was 225 and 324 kittiwakes for the Developer and Scoping Approaches respectively (
     Table 3 Estimated number of collisions for kittiwake by season in the Proposed Development Array for the worst-case scenario (SNCBs avoidance rates, turbine 14 MW, Option 1) using boat-based data).    
110. The annual estimate of gannet collisions was 153 birds for the Developer Approach and 191 birds for Scoping Approach.  
111. For herring gull, the worst-case estimate was 30 birds per annum based on the Developer Approach and 50 for the Scoping Approach; for all other species, annual estimated collisions based on the Developer Approach were of eight birds or less, compared with 14 birds or less using the Scoping Approach. Near zero collisions for great skua were predicted using both Approaches. 

112. The view that using fewer, larger turbines as an effective measure for reducing collision (Johnston et al., 2014a; 2014b) was borne out by the modelling using Band Option 2 undertaken here. For all species, the number of collisions tended to decrease with increasing turbine size and (amongst the three larger turbine models which had different chord width and rotor speed Options) was lower for Type B turbines (narrower chord and faster rotational speed).  
113. The embedded mitigation in the turbine design, that increases the air gap from 22 m to 37 m (LAT) results in a reduction in the estimated annual number of collisions of ~76% and 79% for kittiwake and gannet respectively.    

7.             References

7. References

Alerstam, T., Rosén, M., Bäckman, J., Ericson, P.G. and Jellgren, O. (2007). Flight speeds among bird species: allometric and phylogenic effects. PLoS Biology, 5(8), e197.

Band, W. (2012). Using a collision risk model to assess bird collision risks for offshore wind farms – with extended method. Report to the Crown Estate Strategic Ornithological Services (SOSS).

Bowgen, K. and Cook, A. (2018). Bird Collision Avoidance: Empirical evidence and impact assessments. JNCC Report No. 614, JNCC, Peterborough, ISSN 0963-8091.

Camphuysen, K.C.J., Fox, T.A.D., Leopold, M.M.F. and Petersen, I.K. (2004). Towards standardised seabirds at sea census techniques in connection with environmental impact assessments for offshore wind farms in the U.K. - A comparison of ship and aerial sampling methods for marine birds, and their applicability to offshore wind farm assessments. Report COWRIE - BAM -02-2002.

Cook, A.S.C.P., Johnston, A., Wright, L.J. and Burton, N.H.K. (2012). Strategic Ornithological Support Services. Project SOSS-02. A review of flight heights and avoidance rates of birds in relation to offshore wind farms. BTO Research Report 618.

Cook, A.S.C.P., Humphreys, E. M., Masden, E. A. and Burton, N. K. H. (2014). The avoidance rates of collision between birds and offshore turbines. Scottish Marine and Freshwater Science Volume 5, Number 16. 263pp.

Cook, A.S.C.P. (2021). Additional analysis to inform SNCBs recommendations regarding collision risk modelling. BTO Research Report 739.

Furness, R.W., Wade, H.M. and Masdfen, E.A. (2013). Assessing vulnerability of marine bird populations to offshore wind farms. Journal of Environmental Management, 119, 56-66. 

Furness, R.W., Garthe, S., Trinder, M., Matthiopoulos, J., Wanless, S. and Jeglinski, J. (2018). Nocturnal flight activity of northern gannets Morus bassanus and implications for modelling collision risk at offshore wind farms. Environmental Impact Assessment Review, 73, 1-6.

Garthe, S. and Hüppop, O. (2004) Scaling possible adverse effects of marine wind farms on seabirds: developing and applying a vulnerability index. Journal of Applied Ecology, 41(4), 724-734.

Johnston, A., Cook, A.S., Wright, L.J., Humphreys, E.M. and Burton, N.H. (2014a). Modelling flight heights of marine birds to more accurately assess collision risk with offshore wind turbines. Journal of Applied Ecology, 51(1), 31-41.

Johnston, A., Cook, A.S., Wright, L.J., Humphreys, E.M. and Burton, N.H. (2014b). Corrigendum to Modelling flight heights of marine birds to more accurately assess collision risk with offshore wind turbines. Journal of Applied Ecology, 51: 1126 -1130.

Jongbloed, R.H. (2016) Flight height of seabirds. A literature study IMARES. Report C024/16.

Marine Scotland. (2017a) Scoping Opinion for the proposed Section 36 Consent and Associated Marine Licence Application for the Revised NnG Offshore Wind Farm and Revised NnG Offshore Transmission Works. Available from http://www.gov.scot/Topics/marine/Licensing/marine/scoping/NnGRev2017/SO-092017

Marine Scotland. (2017b). Scoping Opinion for the proposed Section 36 Consent and Associated Marine Licence Application for the revised Inch Cape offshore wind farm and revised Inch Cape Offshore Transmission Works.

Masden, E. (2015). Developing an Avian Collision Risk Mode to Incorporate Variability and Uncertainty. Scottish Marine and Freshwater Science Vol 6 No 14. Edinburgh: Scottish Government, 43pp.

McGregor, R.M., King, S., Donovan, C.R., Caneco, B. and Webb, A. (2018). A Stochastic Collision Risk Model for Seabirds in Flight. Report for Marine Scotland.

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Parker, J., Fawcett, A., Banks, A., Rowson, T., Allen, S., Rowell, H., Harwood, A., Ludgate, C., Humphrey, O., Axelsson, M., Baker, A. and Copley, V. (2022). Offshore Wind Marine Environmental Assessments: Best Practice Advice for Evidence and Data Standards. Phase III: Expectations for data analysis and presentation at examination for offshore wind applications. Natural England. Version 1.2. 140 pp.

Pennycuick, C.J. (1997). Actual and ‘Optimum’ Flight speed: Field Data Reassessed. Journal of Experimental Biology, 200(17), 2355-2361.

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Annex A. To The Ornithology Collision Risk Modeling Technical Report: Worst Case Scenario 22 m Air Gap Collision Estimates

Annex A. To The Ornithology Collision Risk Modeling Technical Report: Worst Case Scenario 22 m Air Gap Collision Estimates

1. The Applicant has chosen wind turbine generators with mitigation embedded in the design. The minimum lower blade tip height has been increased from 22 m to 37 m (LAT) as an engineering design measure to increase the lower air gap. The larger air gap was predicted to have a positive impact on reducing the number of seabirds at risk of collision with the turbines. The Scoping Opinion requires that any embedded mitigation relied upon for the purposes of the assessment should be clearly and accurately explained in detail within the EIA Report.

2. Therefore, Collision Risk Models (CRMs) were run using the deterministic Band on the worst-case scenario (SNCBs (2014) avoidance rates, turbine 14 MW, Type A) for both kittiwake (Table 1) and gannet (Table 2), for both the Developer and Scoping Approaches, but the hub height relative to LAT, reduced from 148 m to 133 m for the results presented in this Annex. All other input parameters were exactly as set out in Section 3.4.
3. The estimated number of collisions were considerably higher with a 22 m airgap compared with the larger 37 m. By using a larger airgap, the estimated number of collisions was ~76% and 79% lower for kittiwake and gannet respectively.

Annex A Table 1 Comparison of the estimated annual collisions for kittiwake in the Proposed Development Array for the worst-case scenario (SNCBs avoidance rates, turbine 14 MW, Type A) with a 22 m and 37 m air gap, based on the Developer and Scoping Approaches. Estimates are presented using the mean avoidance rate (0.989) and for the mean avoidance rate ±2 SD (0.002). Estimates are rounded to the nearest whole

Annex A Table 2 Comparison of the estimated annual collisions for gannet in the Proposed Development Array for the worst-case scenario (SNCBs avoidance rates, turbine 14 MW, Type A) with a 22 m and 37 m air gap, based on the Developer and Scoping Approaches. Estimates are presented using the mean avoidance rate (0.989) and for the mean avoidance rate ±2 SD (0.002). Estimates are rounded to the nearest whole

Annex B. To The Ornithology Collision Risk Modelling Technical Report: Boat-Based Kittiwake Collision Estimates