Summary of PVA Assessment

289. PVA was carried out for guillemot considering a wide range of displacement and mortality rates. The results of the PVAs for predicted displacement impacts for the Project alone during the operation phase for the guillemot regional SPA population for the 35-year projection is summarised in Table 11.34   Open ▸ . Further details of the PVA methodology, input parameters and an explanation of how to interpret the PVA results can be found in volume 3, appendix 11.6.

Table 11.34: Summary of PVA Displacement Outputs for Guillemot for the Proposed Development array area plus 2 km buffer after 35 years

1 Starting population taken from volume 3, appendix 11.6
Developer Approach = 50% displacement and 1% mortality throughout year
Scoping Approach A = 60% displacement and 3% displacement mortality in breeding season; 1% displacement mortality in non-breeding season.
Scoping Approach B = 60% displacement and 5% displacement mortality in breeding season; 3% displacement mortality in non-breeding season.

290. For both the with and without Project scenarios, the guillemot regional SPA population is predicted to increase over the 35-year period. For the Developer Approach, the end population size with Project scenario was slightly lower than the without Project scenario. There was a very slight predicted decrease in the counterfactual of the population growth rate, and the counterfactual of the population size was also close to 1.000, while the 50th Centile value was relatively close to 50. These values indicate that the PVA did not predict a significant negative effect from the project alone effects of displacement mortality from the Developer Approach on the guillemot regional SPA population after 35 years.
291. For Scoping Approach A, the end population size with Project scenario was lower than the without Project scenario. There was a very slight predicted decrease in the counterfactual of the population growth rate, and the counterfactual of the population size was lower than 1.000, while the 50th Centile value was 24.1. These values indicate that the PVA did predict a slight negative effect from the project-alone effects of displacement mortality from Scoping Approach A on the guillemot regional SPA guillemot population after 35 years.
292. For Scoping Approach B, the end population size with Project scenario was lower than the without Project scenario. There was a slight predicted decrease in the counterfactual of the population growth rate, and the counterfactual of the population size was lower, while the 50th Centile value was 8.7. These values indicate that the PVA did predict a larger negative effect from the project-alone effects of displacement mortality from Scoping Approach B on the guillemot regional SPA guillemot population after 35 years.
293. Based on the results from the displacement assessment and the regional PVA for the Developer Approach, the magnitude of impact on the regional guillemot population is low.
294. Based on the results from the displacement assessment and the regional PVA for Scoping Approach A, the magnitude of impact is low.
295. Based on the results from the displacement assessment and the regional PVA for Scoping Approach B, the magnitude of impact is medium.

Sensitivity of the Receptor

296. For this assessment, receptor sensitivity has been based on three reviews of evidence from post-construction studies at offshore wind farms. A review of post-construction studies of seabirds at offshore wind farms in European waters concluded that the mean outcome across 13 offshore wind farms for auks was ‘weak displacement’ but this was highly variable. Overall, the review concluded that there was evidence that guillemot was one of the species which showed a weak avoidance of offshore wind farms (Dierschke et al., 2016).
297. A review of vulnerability of Scottish seabirds to offshore wind turbines in the context of disturbance and displacement ranked guillemot with a score of three, where five was the most vulnerable score and one was the least vulnerable (Furness and Wade, 2012). A subsequent review ranked guillemot with a score of 14, where the highest score was 32 (Furness et al., 2013). Bradbury et al., (2014), classified the guillemot population vulnerability to displacement from offshore wind farms as moderate. Further evidence of the degree of displacement from operational offshore wind farms on guillemots is presented in volume 3, appendix 11.4.
298. On the basis of the evidence from reviews presented above and from post-construction studies summarised in volume 3, appendix 4, guillemot sensitivity to operational offshore wind farms is considered to be medium ( Table 11.16   Open ▸ ).
299. Estimated numbers of guillemots recorded within the Proposed Development array area would qualify as internationally important in the breeding season, as estimated numbers regularly exceeded 20,000 birds (See volume 3, appendix 11.1, annex K), with individuals likely originating from a number of SPAs and non-SPAs in the region. On this basis the conservation importance for guillemot was considered to be high.

Significance of the Effect

300. For displacement effects on guillemot from the Project alone, for the Developer Approach, the magnitude of the impact is deemed to be low, 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.
301. For Scoping Approach A, the magnitude of the impact is deemed to be low, 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.
302. For Scoping Approach B, the magnitude of the impact is deemed to be medium, and the sensitivity of the receptor is considered to be medium. The effect will, therefore, be of moderate adverse significance, which is significant in EIA terms.

Secondary and Tertiary Mitigation and Residual Effect

303. For the Developer Approach and Scoping Approach A, no offshore and intertidal ornithology mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 11.10) is not significant in EIA terms. Therefore, the residual impact is considered to be of minor adverse significance, which is not significant in EIA terms.
304. For Scoping Approach B, the residual impact is considered to be of moderate adverse significance, which is significant in EIA terms. However, it is considered that the displacement mortality rates used in Scoping Approach B are likely to be highly precautionary, for the reasons outlined in volume 3, appendix 11.4. Consequently, no additional mitigation is proposed.

Razorbill

305. For the Developer Approach displacement assessment, a displacement rate of 50% 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.
306. There were two parts to the Scoping Approach displacement assessment and these are outlined below. For Scoping Approach A, a displacement rate of 60% and mortality rates of 3% for the breeding season and 1% for the non-breeding season were applied. For Scoping Approach B, a displacement rate of 60% and mortality rates of 5% for the breeding season and 3% for the non-breeding season were applied.
307. Further details of differences between the Developer Approach and the Scoping Approach for the displacement assessment are presented in volume 3, appendix 11.4.

Magnitude of Impact

308. In the breeding season, peak estimates of razorbills in the Proposed Development array area and 2 km buffer in the were recorded in July 2019 (3,258 birds) and August 2020 (4,820 birds), which gave a MSP of 4,040 birds in the breeding season. In the autumn migration period of the non-breeding season, peak estimates were 2,111 birds in September 2019 and 15,587 birds in September 2020, which gave a MSP of 8,849 birds over the period. In the winter period of the non-breeding season, peak estimates were 632 birds in December 2019 and 2,165 birds in December 2020, which gave a MSP of 1,399 birds over the period. Peak estimated numbers in the spring migration period of the non-breeding season, were 9,130 birds in March 2020 and 5,830 birds in April 2021, which gave a MSP of 7,480 birds over the period (see volume 3, appendix 11.4).
309. A complete range of displacement matrices for the Proposed Development, the Proposed Development array area and 2 km buffer as well as for the different bio-seasons for both the Developer Approach and the Scoping Approach are presented in volume 3, appendix 11.4.
310. For the Developer Approach, annual estimated razorbill mortality from displacement in the Proposed Development and a 2 km buffer is presented in Table 11.35   Open ▸ .
311. For the Scoping Approach, annual estimated razorbill mortality from displacement in the Proposed Development and a 2 km buffer is presented in Table 11.36   Open ▸ and Table 11.37   Open ▸ . For both approaches, the impact of additional mortality due to wind farm effects has been assessed in terms of the change in the baseline mortality rate which could result. The overall baseline mortality rates were based on age-specific demographic rates and age class proportions from the PVA work as presented in Table 11.21   Open ▸ . The potential magnitude of impact was estimated by calculating the increase in baseline mortality within each bio-season with respect to the regional populations.
312. For the breeding season assessments, the increase in baseline mortality was calculated based on the baseline adult survival rate presented in Table 11.21   Open ▸ . For razorbill, the adult baseline survival rate is estimated to be 0.910, therefore the corresponding rate for adult mortality is 0.09. For the non-breeding season assessments, 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. Therefore, a weighted average baseline mortality rate has been calculated which is appropriate for all age classes for use in assessments, calculated for those species screened in for assessment. These were calculated using the different survival rates for each age class and their relative proportions in the population ( Table 11.21   Open ▸ ).

Table 11.35: Displacement Mortality Estimates for Razorbill for the Proposed Development array area plus 2 km buffer by bio-season for the Developer Approach

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

Table 11.36: Displacement Mortality Estimates for Razorbill for the Proposed Development array area plus 2 km buffer by bio-season for Scoping Approach A

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

Table 11.37: Displacement Mortality Estimates for Razorbill for the Proposed Development array area plus 2 km buffer by bio-season for Scoping Approach B

1 Breeding season assessment is for breeding adults only.
2 Mortality is 5% in breeding season and 3% in non-breeding season.

Breeding Season

313. During the breeding season, the mean peak abundance for razorbill was 4,040 individuals within the Proposed Development array area and 2 km buffer. When considering the Developer Approach displacement rate of 50% in the Proposed Development array area and 2 km buffer, this would affect an estimated 2,020 birds ( Table 11.35   Open ▸ ). However, this estimate includes non-breeding adults and immature birds, as well as breeding adults.
314. 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, this has been estimated using proportions from the stable age structure calculated from the population models from which PVAs were produced ( Table 11.38   Open ▸ ) (volume 3, appendix 11.6).

Table 11.38: PVA Stable Age Structure for Razorbills

315. Based on the proportion of immature razorbills from the stable age structure, 46.6% of the population present are immature birds ( Table 11.38   Open ▸ ). This would mean that an estimated 941 razorbills displaced from the Proposed Development array area and 2 km buffer during the breeding season would be immature birds, with 1,079 adult birds also displaced.
316. Applying the Developer Approach mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 21 razorbills (11 adults and ten immature birds) 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 7% of adult razorbills 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, one adult razorbill was considered to be not breeding and so ten adult breeding razorbills were taken forward for the breeding season assessment.
317. The total razorbill regional baseline breeding population is estimated to be 84,501 individuals ( Table 11.9   Open ▸ ). The adult baseline survival rate for razorbill is estimated to be 0.910 ( Table 11.21   Open ▸ ), which means that the corresponding rate for adult mortality is 0.09. Applying this mortality rate, the estimated regional baseline mortality of adult razorbills is 7,605 birds per breeding season. The additional predicted mortality of ten breeding adult razorbills would increase the baseline mortality rate by 0.13% ( Table 11.35   Open ▸ ).
318. When considering the Scoping Approach displacement rate of 60% in the Proposed Development array area and 2 km buffer, this would affect an estimated 2,425 birds. Assuming that 46.6% of the population present are immature birds ( Table 11.38   Open ▸ ), then this would mean that an estimated 1,130 razorbills displaced from the Proposed Development array area and 2 km buffer during the breeding season would be immature birds, with 1,295 adult birds also displaced.
319. Applying the Scoping Approach A mortality rate of 3% for the breeding season, it was calculated that the predicted theoretical additional mortality due to displacement effects was 73 razorbills (39 adults and 34 immature birds) in the breeding season. As above, a sabbatical rate of 7% for non-breeding adult razorbills (volume 3, appendix 11.6) has been applied for this assessment. This resulted in three adult razorbills being considered to be not breeding and so 36 adult breeding razorbills were taken forward for the breeding season assessment.
320. Applying a mortality rate for adult razorbills of 0.09, the estimated regional baseline mortality of razorbills is 7,605 adult breeding birds per breeding season. The additional predicted mortality of 36 breeding adult razorbills would increase the baseline mortality rate by 0.47% ( Table 11.36   Open ▸ ).
321. Applying the Scoping Approach B mortality rate of 5% for the breeding season, it was calculated that the predicted theoretical additional mortality due to displacement effects was 122 razorbills (65 adults and 57 immature birds) 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. Applying a proportion of 7% for “sabbatical” adult razorbills (volume 3, appendix 11.6), resulted in five adult razorbills being considered to be not breeding and so 60 adult breeding razorbills were taken forward for the breeding season assessment.
322. Applying a mortality rate for adult razorbills of 0.09, the estimated regional baseline mortality of razorbills is 7,605 adult breeding birds per breeding season. The additional predicted mortality of 60 breeding adult razorbills would increase the baseline mortality rate by 0.79% ( Table 11.37   Open ▸ ).

Non-breeding Season – Autumn Migration Period

323. For the autumn migration period of the non-breeding season, the mean peak abundance for razorbill was 8,849 individuals within the Proposed Development array area and 2 km buffer. When considering the Developer Approach displacement rate of 50% in the Proposed Development array area and 2 km buffer, this would affect an estimated 4,424 birds ( Table 11.35   Open ▸ ).
324. Based on the proportion of immature razorbills from the stable age structure, 46.6% of the population present in the autumn migration period are immature birds ( Table 11.38   Open ▸ ). This would mean that an estimated 2,062 razorbills displaced from the Proposed Development array area and 2 km buffer during the autumn migration period would be immature birds, with 2,362 adult birds also displaced.
325. Applying the Developer Approach mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 44 razorbills (23 adults and 21 immature birds) in the autumn migration period. Based on Furness (2015), the total razorbill BDMPS regional baseline population for the autumn migration period is estimated to be 591,874 individuals ( Table 11.9   Open ▸ ). Using the average baseline mortality rate of 0.12 ( Table 11.21   Open ▸ ), the estimated regional baseline mortality of razorbills is 71,025 birds in the autumn migration period of the non-breeding season. The additional predicted mortality of 44 razorbills would increase the baseline mortality rate by 0.062% ( Table 11.35   Open ▸ ).
326. When considering the Scoping Approach displacement rate of 60% in the Proposed Development array area and 2 km buffer, this would affect an estimated 5,309 birds ( Table 11.36   Open ▸ and Table 11.37   Open ▸ ). Assuming that 46.6% of the population present are immature birds ( Table 11.38   Open ▸ ), then this would mean that an estimated 2,474 razorbills displaced from the Proposed Development array area and 2 km buffer during the autumn migration period of the non-breeding season would be immature birds, with 2,835 adult birds also displaced.
327. Applying the Scoping Approach A mortality rate of 1% in the non-breeding season, it was calculated that the predicted theoretical additional mortality due to displacement effects was 53 razorbills (28 adults and 25 immature birds) in the autumn migration period. The additional predicted mortality of 53 razorbills would increase the baseline mortality rate by 0.075% ( Table 11.36   Open ▸ ).
328. Applying the Scoping Approach B mortality rate of 3% in the non-breeding season, it was calculated that the predicted theoretical additional mortality due to displacement effects was 159 razorbills (85 adults and 74 immature birds) in the autumn migration period. The additional predicted mortality of 159 razorbills would increase the baseline mortality rate by 0.224% ( Table 11.37   Open ▸ ).

Non-breeding Season – Winter Period

329. For the winter period of the non-breeding season, the mean peak abundance for razorbill was 1,399 individuals within the Proposed Development array area and 2 km buffer. When considering the Developer Approach displacement rate of 50% in the Proposed Development array area and 2 km buffer, this would affect an estimated 700 birds ( Table 11.35   Open ▸ ).
330. Based on the proportion of immature razorbills from the stable age structure, 46.6% of the population present in the winter period are immature birds ( Table 11.38   Open ▸ ). This would mean that an estimated 326 razorbills displaced from the Proposed Development array area and 2 km buffer during the winter period would be immature birds, with 374 adult birds also displaced.
331. Applying the Developer Approach mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was seven razorbills (four adults and three immature birds) in the winter period. Based on Furness (2015), the total razorbill BDMPS regional baseline population for the winter period is estimated to be 218,622 individuals ( Table 11.9   Open ▸ ). Using the average baseline mortality rate of 0.12 ( Table 11.21   Open ▸ ), the estimated regional baseline mortality of razorbills is 26,235 birds in the winter period. The additional predicted mortality of seven razorbills would increase the baseline mortality rate by 0.027%.
332. When considering the Scoping Approach displacement rate of 60% in the Proposed Development array area and 2 km buffer, this would affect an estimated 839 birds ( Table 11.36   Open ▸ and Table 11.37   Open ▸ ). Assuming that 46.6% of the population present are immature birds ( Table 11.38   Open ▸ ), then this would mean that an estimated 391 razorbills displaced from the Proposed Development array area and 2 km buffer during the winter period of the non-breeding season would be immature birds, with 448 adult birds also displaced.
333. Applying the Scoping Approach A mortality rate of 1% in the non-breeding season, it was calculated that the predicted theoretical additional mortality due to displacement effects was eight razorbills (four adults and four immature birds) in the winter period. The additional predicted mortality of eight razorbills would increase the baseline mortality rate by 0.03% ( Table 11.36   Open ▸ ).
334. Applying the Scoping Approach B mortality rate of 3% in the non-breeding season, it was calculated that the predicted theoretical additional mortality due to displacement effects was 25 razorbills (13 adults and 12 immature birds) in the winter period. The additional predicted mortality of 25 razorbills would increase the baseline mortality rate by 0.095% ( Table 11.37   Open ▸ ).

Non-breeding Season – Spring Migration Period

335. For the spring migration period of the non-breeding season, the mean peak abundance for razorbill was 7,480 individuals within the Proposed Development array area and 2 km buffer. When considering the Developer Approach displacement rate of 50% in the Proposed Development array area and 2 km buffer, this would affect an estimated 3,740 birds ( Table 11.35   Open ▸ ).
336. Based on the proportion of immature razorbills from the stable age structure, 46.6% of the population present in the spring migration period are immature birds ( Table 11.38   Open ▸ ). This would mean that an estimated 1,743 razorbills displaced from the Proposed Development array area and 2 km buffer during the spring migration period would be immature birds, with 1,997 adult birds also displaced.
337. Applying the Developer Approach mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 37 razorbills (20 adults and 17 immature birds) in the spring migration period. Based on Furness (2015), the total razorbill BDMPS regional baseline population for the spring migration period is estimated to be 591,874 individuals ( Table 11.9   Open ▸ ). Using the average baseline mortality rate of 0.12 ( Table 11.21   Open ▸ ), the estimated regional baseline mortality of razorbills is 71,025 birds in the spring migration period. The additional predicted mortality of 37 razorbills would increase the baseline mortality rate by 0.052% ( Table 11.35   Open ▸ ).
338. When considering the Scoping Approach displacement rate of 60% in the Proposed Development array area and 2 km buffer, this would affect an estimated 4,488 birds ( Table 11.36   Open ▸ and Table 11.37   Open ▸ ). Assuming that 46.6% of the population present are immature birds ( Table 11.38   Open ▸ ), then this would mean that an estimated 2,091 razorbills displaced from the Proposed Development array area and 2 km buffer during the spring migration period of the non-breeding season would be immature birds, with 2,397 adult birds also displaced.
339. Applying the Scoping Approach A mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 45 razorbills (24 adults and 21 immature birds) in the spring migration period. The additional predicted mortality of 45 razorbills would increase the baseline mortality rate by 0.063% ( Table 11.36   Open ▸ ).
340. Applying the Scoping Approach B mortality rate of 3%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 135 razorbills (72 adults and 63 immature birds) in the spring migration period. The additional predicted mortality of 135 razorbills would increase the baseline mortality rate by 0.19% ( Table 11.37   Open ▸ ).

Assessment of Displacement Mortality throughout the Year

341. Predicted razorbill mortality as a result of displacement in the Proposed Development array area and 2 km buffer for all bio-seasons as calculated above, was summed for the whole year.
342. Based on the Developer Approach displacement rate of 50% and mortality rate of 1%, the predicted theoretical additional annual mortality due to displacement effects is an estimated 98 razorbills each year. This corresponds to an increase in the baseline mortality rate of 0.27% ( Table 11.35   Open ▸ ).
343. Applying the Scoping Approach A displacement rate of 60% and mortality rates of 3% in the breeding season and 1% in the non-breeding season, the predicted theoretical additional annual mortality due to displacement effects is an estimated 142 razorbills each year. This corresponds to an increase in the baseline mortality rate of 0.64% ( Table 11.36   Open ▸ ).
344. Applying the Scoping Approach B displacement rate of 60% and mortality rates of 5% in the breeding season and 3% in the non-breeding season, the predicted theoretical additional annual mortality due to displacement effects is an estimated 379 razorbills each year. This corresponds to an increase in the baseline mortality rate of 1.30% ( Table 11.37   Open ▸ ).
345. These displacement mortality estimates suggest a potential significant increase in the baseline mortality rate for razorbill for Scoping Approach B therefore PVA analysis was conducted on the razorbill regional SPA population.

Summary of PVA Assessment

346. PVA has been carried out for razorbill considering a wide range of displacement and mortality rates. The results of the PVAs for predicted displacement impacts for the Project alone during the operational phase for the razorbill regional SPA population for the 35-year projection is summarised in Table 11.39   Open ▸ . Further details of the PVA methodology, input parameters and an explanation of how to interpret the PVA results can be found in volume 3, appendix 11.6.

Table 11.39: Summary of PVA Displacement outputs for Razorbill for the Proposed Development array area plus 2 km buffer after 35 years

1 Starting population taken from volume 3, appendix 11.6.
Developer Approach = 50% displacement and 1% mortality throughout year.
Scoping Approach A = 60% displacement and 3% displacement mortality in breeding season; 1% displacement mortality in non-breeding season.
Scoping Approach B = 60% displacement and 5% displacement mortality in breeding season; 3% displacement mortality in non-breeding season.

347. For both the with and without Project scenarios, the razorbill regional SPA population is predicted to increase over the 35-year period. For the Developer Approach, the end population size with Project scenario was very slightly lower than the without Project scenario. There was no predicted difference in the counterfactual of the population growth rate, and the counterfactual of the population size was also very close to 1.000, while the 50th Centile value was close to 50. These values indicate that the PVA did not predict a significant negative effect from the project alone effects of displacement mortality from the Developer Approach on the razorbill regional SPA population after 35 years.
348. For Scoping Approach A, the end population size with Project scenario was slightly lower than the without Project scenario. There was no predicted difference in the counterfactual of the population growth rate, and the counterfactual of the population size was also close to 1.000, while the 50th Centile value was close to 50. These values indicate that the PVA did not predict a significant negative effect from the project alone effects of displacement mortality from Scoping Approach A on the razorbill regional SPA population after 35 years.
349. For Scoping Approach B, the end population size with Project scenario was slightly lower than the without Project scenario. There was a very slight predicted difference in the counterfactual of the population growth rate, and the counterfactual of the population size was also close to 1.000, while the 50th Centile value was also close to 50. These values indicate that the PVA did not predict a significant negative effect from the project alone effects of displacement mortality from Scoping Approach B on the razorbill regional SPA population after 35 years.
350. Based on the results from the displacement assessment and the regional PVA for the Developer Approach and Scoping Approach A, the magnitude of impact on the regional razorbill population is negligible.
351. Based on the results from the displacement assessment and the regional PVA for Scoping Approach B, the magnitude of impact on the regional razorbill population is low.

Sensitivity of the Receptor

352. For this assessment, receptor sensitivity has been based on three reviews of evidence from post-construction studies at offshore wind farms. A review of post-construction studies of seabirds at offshore wind farms in European waters concluded that there was evidence that razorbill was one of the species which showed a weak avoidance of offshore wind farms (Dierschke et al., 2016).
353. A review of vulnerability of Scottish seabirds to offshore wind turbines in the context of disturbance and displacement ranked razorbill with a score of three, where five was the most vulnerable score and one was the least vulnerable (Furness and Wade, 2012). A subsequent review ranked razorbill with a score of 14, where the highest score was 32 (Furness et al., 2013). Bradbury et al., (2014), classified the razorbill population vulnerability to displacement from offshore wind farms as moderate. Further evidence of the degree of displacement from operational offshore wind farms on razorbills is presented in volume 3, appendix 11.4.
354. On the basis of the evidence from reviews presented above and from post-construction studies summarised in volume 3, appendix 4, razorbill sensitivity to operational offshore wind farms is considered to be medium ( Table 11.16   Open ▸ ).
355. Estimated numbers of razorbills recorded within the Proposed Development array area would qualify as nationally important in the breeding season (See volume 3, appendix 11.1, annex K), with individuals likely originating from a number of SPAs and non-SPAs in the region. On this basis, the conservation importance for razorbill was considered to be medium.

Significance of the Effect

356. For displacement effects on razorbill from the Project alone, for the Developer 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.
357. For Scoping Approach A, 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.
358. For Scoping Approach B, the magnitude of the impact is deemed to be low, 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 and Tertiary Mitigation and Residual Effect

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

Puffin

360. For the Developer Approach displacement assessment, a displacement rate of 50% and a mortality rate of 1% was applied for the breeding season only, based on an evaluation of the published literature and in line with values used by other offshore wind farm displacement assessments.
361. There were two parts to the Scoping Approach displacement assessment and these are outlined below. For Scoping Approach A, a displacement rate of 60% and a mortality rate of 3% was applied for the breeding season only. For Scoping Approach B, a displacement rate of 60% and a mortality rate of 5% was applied for the breeding season only.
362. For both the Developer Approach and the Scoping Approaches, there was no requirement to assess puffin displacement in the non-breeding season, as per advice in the Scoping Opinion.
363. Further details of differences between the Developer Approach and the Scoping Approach for the displacement assessment are presented in volume 3, appendix 11.4.

Magnitude of Impact

364. In the breeding season, peak estimates of puffins in the Proposed Development array area and 2 km buffer were recorded in April 2019 (6,280 birds) and August 2020 (2,745 birds). The MSP for the breeding season was therefore 4,513 birds (see volume 3, appendix 11.4).
365. A complete range of displacement matrices for the Proposed Development, the Proposed Development array area and 2 km buffer in the breeding season for both the Developer Approach and the Scoping Approaches are presented in volume 3, appendix 11.4.
366. For the Developer Approach, estimated puffin mortality from displacement in the breeding season in the Proposed Development array area and 2 km buffer is presented in Table 11.40   Open ▸ .
367. For the Scoping Approach, estimated puffin mortality from displacement in the breeding season Proposed Development array area and 2 km buffer is presented in Table 11.41   Open ▸ and Table 11.42   Open ▸ . For both approaches, the impact of additional mortality due to wind farm effects has been assessed in terms of the change in the baseline mortality rate which could result. The overall baseline mortality rates were based on age-specific demographic rates and age class proportions from the PVA work as presented in Table 11.21   Open ▸ . The potential magnitude of impact was estimated by calculating the increase in baseline mortality within each bio-season with respect to the regional populations.
368. For the breeding season assessments, the increase in baseline mortality was calculated based on the baseline adult survival rate presented in Table 11.21   Open ▸ . For puffin, the adult baseline survival rate is estimated to be 0.901, therefore the corresponding rate for adult mortality is 0.09.

Table 11.40: Displacement Mortality Estimates for Puffin for the Proposed Development array area plus 2 km buffer in the Breeding Season for the Developer Approach

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

Table 11.41: Displacement Mortality Estimates for Puffin for the Proposed Development array area plus 2 km buffer in the Breeding Season for Scoping Approach A

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

Table 11.42: Displacement Mortality Estimates for Puffin for the Proposed Development array area plus 2 km buffer in the Breeding Season for Scoping Approach B

1 Breeding season assessment is for breeding adults only.
2 Mortality is 5% in breeding season.

Breeding Season

369. During the breeding season, the mean peak abundance for puffin was 4,513 individuals within the Proposed Development array area and 2 km buffer. When considering the Developer Approach displacement rate of 50% in the Proposed Development array area and 2 km buffer, this would affect an estimated 2,257 birds ( Table 11.40   Open ▸ ). However, this estimate includes non-breeding adults and immature birds, as well as breeding adults.
370. 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, this has been estimated using proportions from the stable age structure calculated from the population models from which PVAs were produced ( Table 11.43   Open ▸ ) (volume 3, appendix 11.6).

Table 11.43: PVA Stable Age Structure for Puffins

371. Based on the proportion of immature puffins from the stable age structure, 50.3% of the population present are immature birds ( Table 11.43   Open ▸ ). This would mean that an estimated 1,135 puffins displaced from the Proposed Development array area and 2 km buffer during the breeding season would be immature birds, with 1,122 adult birds also displaced.
372. Applying the Developer Approach mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 23 puffins (11 adults and 12 immature birds) 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 7% of adult puffins 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, one adult puffin was considered to be not breeding and so ten adult breeding puffins were taken forward for the breeding season assessment.
373. The total puffin regional baseline breeding population is estimated to be 233,550 individuals ( Table 11.9   Open ▸ ). The adult baseline survival rate for puffin is estimated to be 0.901 ( Table 11.21   Open ▸ ), which means that the corresponding rate for adult mortality is 0.099. Applying this mortality rate, the estimated regional baseline mortality of puffins is 23,121 adult birds per breeding season. The additional predicted mortality of ten breeding adult puffins would increase the baseline mortality rate by 0.043% ( Table 11.40   Open ▸ ).
374. When considering the Scoping Approach displacement rate of 60% in the Proposed Development array area and 2 km buffer, this would affect an estimated 2,708 birds ( Table 11.41   Open ▸ and Table 11.42   Open ▸ ). However, this estimate includes non-breeding adults and immature birds, as well as breeding adults. Assuming that 50.3% of the population present are immature birds ( Table 11.43   Open ▸ ), then this would mean that an estimated 1,362 puffins displaced from the Proposed Development array area and 2 km buffer during the breeding season would be immature birds, with 1,346 adult birds also displaced.
375. Applying the Scoping Approach A mortality rate of 3%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 82 puffins (41 adults and 41 immature birds) in the breeding season. As above, a sabbatical rate of 7% for non-breeding adult puffins (volume 3, appendix 11.6) has been applied for this assessment. On this basis, three adult puffins were considered to be not breeding and so 38 adult breeding puffins were taken forward for the breeding season assessment.
376. Applying the adult mortality rate of 0.099, the estimated regional baseline mortality of puffins is 23,121 adult birds per breeding season. The additional predicted mortality of 38 breeding adult puffins would increase the baseline mortality rate by 0.16% ( Table 11.41   Open ▸ ).
377. Applying the Scoping Approach B mortality rate of 5%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 136 puffins (68 adults and 68 immature birds) in the breeding season. However, it has been estimated that 7% of adult puffins may be “sabbatical” non-breeding birds in any particular breeding season (volume 3, appendix 11.6), and this has been applied for this assessment. On this basis, five adult puffins were considered to be not breeding and so 63 adult breeding puffins were taken forward for the breeding season assessment.
378. Applying the adult mortality rate of 0.099, the estimated regional baseline mortality of puffins is 23,121 adult birds per breeding season. The additional predicted mortality of 63 breeding adult puffins would increase the baseline mortality rate by 0.27% ( Table 11.42   Open ▸ ).
379. Although these displacement mortality estimates did not suggest a potential significant increase in the baseline mortality rate for puffin for the Developer or Scoping Approaches, PVA analysis was conducted on the puffin regional SPA population.

Summary of PVA Assessment

PVA has been carried out for puffin considering a wide range of displacement and mortality rates. The results of the PVAs for predicted displacement impacts for the Project alone during the operational phase for the puffin regional SPA population for the 35-year projection is summarised in Table 11.44   Open ▸ . Further details of the PVA methodology, input parameters and an explanation of how to interpret the PVA results can be found in volume 3, appendix 11.6.

Table 11.44: Summary of PVA Displacement outputs for Puffin for the Proposed Development array area plus 2 km buffer after 35 years

1 Starting population taken from volume 3, appendix 11.6.
Developer Approach = 50% displacement and 1% mortality throughout year.
Scoping Approach A = 60% displacement and 3% displacement mortality in breeding season; 1% displacement mortality in non-breeding season.
Scoping Approach B = 60% displacement and 5% displacement mortality in breeding season; 3% displacement mortality in non-breeding season.

380. For both the with and without Project scenarios, the puffin regional SPA population is predicted to increase over the 35-year period. For the Developer Approach, the end population size with Project scenario was slightly lower than the without Project scenario. There was no predicted difference in the counterfactual of the population growth rate, and the counterfactual of the population size was also very close to 1.000, while the 50th Centile value was close to 50. These values indicate that the PVA did not predict a significant negative effect from the project alone effects of displacement mortality from the Developer Approach on the puffin regional SPA population after 35 years.
381. For Scoping Approach A, the end population size with Project scenario was lower than the without Project scenario. There was no predicted difference in the counterfactual of the population growth rate, and the counterfactual of the population size was also close to 1.000, while the 50th Centile value was close to 50. These values indicate that the PVA did not predict a significant negative effect from the project alone effects of displacement mortality from Scoping Approach A on the puffin regional SPA population after 35 years.
382. For Scoping Approach B, the end population size with Project scenario was lower than the without Project scenario. There was no predicted difference in the counterfactual of the population growth rate, and the counterfactual of the population size was also close to 1.000, while the 50th Centile value was also close to 50. These values indicate that the PVA did not predict a significant negative effect from the project alone effects of displacement mortality from Scoping Approach B on the puffin regional SPA population after 35 years.
383. Based on the results from the displacement assessment and the regional PVA for the Developer Approach and Scoping Approaches A and B, the magnitude of impact on the regional puffin population is considered to be negligible.

Sensitivity of the Receptor

384. Previous reviews of displacement effects concluded that results for guillemot and razorbill should also be applied for puffin (e.g. Dierschke et al. 2016 and APEM, 2022). A review of vulnerability of Scottish seabirds to offshore wind turbines in the context of disturbance and displacement ranked puffin with a score of two, where five was the most vulnerable score and one was the least vulnerable (Furness and Wade, 2012). A subsequent review ranked puffin with a score of ten, where the highest score was 32 (Furness et al., 2013). Bradbury et al., (2014), classified the puffin population vulnerability to displacement from offshore wind farms as low. Further evidence of the degree of displacement from operational offshore wind farms on puffins is presented in volume 3, appendix 11.4.
385. On the basis of the evidence from reviews presented above and from post-construction studies summarised in volume 3, appendix 4, puffin sensitivity to operational offshore wind farms is considered to be medium ( Table 11.16   Open ▸ ).
386. Estimated numbers of puffins recorded within the Proposed Development array area would qualify as nationally important in the breeding season (see appendix 11.1, annex K), with individuals likely originating from a number of SPAs and non-SPAs in the region. On this basis the conservation importance for puffin was considered to be medium.

Significance of the Effect

387. For displacement effects on puffin from the Project alone, for the Developer 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.
388. For Scoping Approach A, 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.
389. For Scoping Approach B, 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

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

Collision effects from wind turbines during operation phase

391. There is potential risk to birds from operating offshore wind farms arising from collision with wind turbines resulting in injury or fatality. This may occur when birds fly through an offshore wind farm whilst foraging for food, commuting between breeding colonies and foraging areas, or during migration.
392. Extensive CRM has been undertaken for the Proposed Development, with detailed methods and results presented in volume 3, appendix 11.3. The Proposed Development will comprise up to 307 wind turbines, with the final number of wind turbines dependent on the capacity of individual wind turbines used, and also environmental and engineering survey results. The PDE considers a range of wind turbines with parameters reflective of potential generating capacities, allowing for a degree of flexibility to account for any anticipated developments in wind turbine technology while still allowing the production of the MDS for the assessment of effects. Consent is therefore sought for the physical parameters of the wind turbines which form the basis of the MDS such as maximum tip height or rotor diameter, as presented in the PDE rather than actual installed capacity of the wind turbine.
393. The maximum design scenario, outlined in Table 11.13   Open ▸ , describes the elements of the proposed project considered within this assessment. In all cases, the 14 MW x 307 wind turbines using the deterministic Band (2012) model resulted in the worst-case scenario. For all species, the number of collisions tended to decrease with increasing wind turbine size. Further details are presented in volume 3, appendix 11.3.
394. Operation and Maintenance Phase
395. Consultation Representations and Advice from MSS and NatureScot (4 February 2022) and discussions through the Ornithology Road Map process (volume 3, appendix 11.8), led to agreement that a CRM assessment was required for eight species:

• gannet;
• herring gull;
• lesser black-backed gull;
• kittiwake;
• little gull;
• common tern;
• Arctic tern; and
• great skua.
  396. These eight species were selected based on their abundance within the Proposed Development, highlighted by the two years of baseline data (volume 3, appendix 11.1), and on evidence about their sensitivity to collision effects (Furness et al., 2013).
  397. Two approaches to CRM were used:
• Deterministic offshore Band CRM (Band, 2012); and
• Stochastic CRM (sCRM) (Masden, 2015; McGregor et al., 2018).
  398. The deterministic Band model was used following the advice issued in the Scoping Opinion (4 February 2022) and provides the primary estimates for assessment of collision risk within the Proposed Development. The sCRM approach, which takes account of the variability around input parameters, was used only for comparative purposes, as agreed via the Ornithology Road Map process and following the Scoping Opinion advice.
  399. Following the advice issued in the Scoping Opinion (4 February 2022), the Applicant determined to undertake a ‘dual assessment’ approach of the collision risk posed by the Proposed Development:
• The ‘Scoping Approach’; and
• The ‘Developer Approach’.
  400. With respect to estimating collision risk, the Developer Approach is largely in accordance with the Scoping Opinion, as the two approaches differ only in their use of input monthly density estimates of flying birds of the assessed species within the Proposed Development. Justification for this difference is presented in volume 3, appendix 11.3.
  401. The Scoping Approach is based on the Scoping Consultation responses from NatureScot and MSS which advised the use of monthly maximum density of relevant seabird species within the Proposed Development in the CRMs.
  402. The Developer Approach follows the approach recommended in the industry guidance (Band, 2012) and as undertaken in all recent UK offshore wind farm assessments that the Applicant is aware of. This approach uses the mean of the two estimates of the density of flying birds within the Proposed Development for each month. The Applicant is unaware of any change to the evidence base to support a change from this approach, noting that in their advice for the revised designs of the Forth and Tay projects MSS stated that an approach of using the maximum monthly density values within the CRM “runs the very high risk of producing an estimated effect that is highly likely to be unreasonable and unrealistically high.” (Marine Scotland, 2017a, Marine Scotland, 2017b).
  403. The CRM assessments for the eight key species are presented below.