Gannet

  1. For the Developer Approach 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.
  2. There were two parts to the Scoping Approach displacement assessment and these are outlined below. For Scoping Approach A, the parameters were the same as for the Developer Approach, (a displacement rate of 70% and a mortality rate of 1% were applied for the breeding and non-breeding seasons). For Scoping Approach B, a displacement rate of 70% and a mortality rate of 3% were applied for the breeding and non-breeding seasons. Scoping Approach A was therefore the same as the Developer Approach.
  3. 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
  1. During the baseline aerial survey programme, gannets were most abundant in the Proposed Development array area plus 2 km buffer in the breeding season. Estimated numbers peaked in August 2019 1 (5,020 birds) and July 2020 (4,449 birds), which gave a MSP of 4,735 birds. Estimated numbers were lower in the non-breeding season, with a peak of 1,081 gannets in October 2019 and 1,919 gannets in November 2020. These months correspond to the autumn migration period of the non-breeding season (Furness, 2015). The MSP for the autumn migration period was therefore 1,500 gannets. Estimated numbers in the spring migration period of the non-breeding season showed lower peaks of 321 gannets in March 2019 and 216 gannets in December 2020, which gave a MSP of 269 gannets for the spring migration period (see volume 3, appendix 11.4).
  2. 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.
  3. For the Developer Approach and Scoping Approach A, annual estimated gannet mortality from displacement in the Proposed Development array area and 2 km buffer is presented in Table 11.23   Open ▸ .
  4. For Scoping Approach B, annual estimated gannet mortality from displacement in the Proposed Development array area and 2 km buffer is presented in Table 11.24   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.
  5. 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 gannet, the adult baseline survival rate is estimated to be 0.954, therefore the corresponding rate for adult mortality is 0.046. 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 11.23:
Displacement Mortality Estimates for Gannet for the Proposed Development array area plus 2 km Buffer by Bio-season based on the Developer Approach (and Scoping Approach A)

Table 11.23: Displacement Mortality Estimates for Gannet for the Proposed Development array area plus 2 km Buffer by Bio-season based on the Developer Approach (and Scoping Approach A)

1 Breeding season assessment is for breeding adults only

2 Mortality is 1% in breeding and non-breeding seasons

 

Table 11.24:
Displacement Mortality Estimates for Gannet for the Proposed Development array area plus 2 km buffer by bio-season based on Scoping Approach B

Table 11.24: Displacement Mortality Estimates for Gannet for the Proposed Development array area plus 2 km buffer by bio-season based on Scoping Approach B

1 Breeding season assessment is for breeding adults only

2 Mortality is 3% in breeding and non-breeding seasons

 

Breeding Season
  1. During the breeding season, the mean peak abundance for gannet was 4,735 individuals within the Proposed Development array area and 2 km buffer. When considering the Developer Approach and Scoping Approach displacement rate of 70% in the Proposed Development array area and 2 km buffer, this would affect an estimated 3,315 birds. However, this estimate includes non-breeding adults and immature birds, as well as breeding adults.
  2. 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 recorded on digital aerial baseline surveys in the Offshore Ornithology study area ( Table 11.25   Open ▸ ) (volume 3, appendix 11.1).

 

Table 11.25:
Proportions of Juvenile, Immature and Adult Gannets Recorded on Digital Aerial Surveys

Table 11.25: Proportions of Juvenile, Immature and Adult Gannets Recorded on Digital Aerial Surveys

 

  1. Based on the proportion of immature gannets recorded on digital aerial baseline surveys in the breeding season, 1% of the population present are immature birds ( Table 11.25   Open ▸ ), Although this is likely to be an underestimate, since it is not possible to age all birds recorded on surveys, this would mean that an estimated 33 gannets displaced from the Proposed Development array area and 2 km buffer during the breeding season would be immature, with 3,282 adult birds also displaced.
  2. Applying the Developer Approach and Scoping Approach A mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 34 gannets (all 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, three adult gannets were considered to be not breeding and so 31 adult breeding gannets were taken forward for the breeding season assessment.
  3. The total gannet regional baseline breeding population is estimated to be 323,836 adult birds ( Table 11.9   Open ▸ ). The adult baseline survival rate is estimated to be 0.954 ( Table 11.21   Open ▸ ), which means that the corresponding rate for adult mortality is 0.046. Applying this mortality rate, the estimated regional baseline mortality of gannets is 14,896 adult birds per breeding season. The additional predicted mortality of 31 breeding adult gannets for the Developer Approach and Scoping Approach A would increase the baseline mortality rate by 0.21% ( Table 11.23   Open ▸ ).
  4. Applying Scoping Approach B mortality rates of 3%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 100 gannets (99 adults and one immature bird) in the breeding season. Accounting for 10% of adult gannets being “sabbatical” birds, this total is revised to 89 breeding adult gannets.
  5. The additional predicted mortality of 89 breeding adult gannets for Scoping Approach B would increase the baseline mortality rate by 0.60% ( Table 11.24   Open ▸ ).
Non-breeding Season – Autumn Migration Period
  1. For the autumn migration period of the non-breeding season, the mean peak abundance for gannet was 1,500 individuals within the Proposed Development array area and 2 km buffer. When considering the Developer Approach and Scoping Approach displacement rate of 70% in the Proposed Development array area and 2 km buffer, this would affect an estimated 1,050 birds ( Table 11.23   Open ▸ and Table 11.24   Open ▸ ).
  2. Based on information presented in Furness (2015), in the non-breeding season 45% of the population present in the autumn migration period are immature birds and 55% of birds are adults. This would mean that an estimated 473 gannets displaced from the Proposed Development array area and 2 km buffer during the autumn migration period would be immature, with 577 adult birds also displaced.
  3. Applying the Developer Approach and Scoping Approach A mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 11 gannets (six adults and five immature birds) in the autumn migration period. Based on Furness (2015), the total gannet BDMPS regional baseline population for the autumn migration period is estimated to be 456,298 individuals ( Table 11.9   Open ▸ ). Using the average baseline mortality rate of 0.151 ( Table 11.21   Open ▸ ), the estimated regional baseline mortality of gannets is 68,901 birds in the autumn migration period. The additional predicted mortality of 11 gannets for the Developer Approach and Scoping Approach A would increase the baseline mortality rate by 0.016% ( Table 11.23   Open ▸ ).
  4. Applying the Scoping Approach B mortality rate 3%, it was calculated that 32 gannets (18 adults and 14 immature birds) displaced from the Proposed Development array area and 2 km buffer in the autumn migration period would suffer mortality as a result. The additional predicted mortality of 32 gannets for Scoping Approach B would increase the baseline mortality rate by 0.046% ( Table 11.24   Open ▸ ).
Non-breeding Season – Spring Migration Period
  1. For the spring migration period of the non-breeding season, the mean peak abundance for gannet was 269 individuals within the Proposed Development array area and 2 km buffer. When considering the Developer Approach and Scoping Approach displacement rate of 70% in the Proposed Development array area and 2 km buffer, this would affect an estimated 188 birds ( Table 11.23   Open ▸ and Table 11.24   Open ▸ ).
  2. Based on information presented in Furness (2015), in the non-breeding season 45% of the population present in the spring migration period are immature birds and 55% of birds are adults. This would mean that an estimated 85 gannets displaced from the Proposed Development array area and 2 km buffer during the spring migration period would be immature, with 103 adult birds also displaced.
  3. Applying the Developer Approach and Scoping Approach A mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was two gannets (one adult and one immature bird) in the spring migration period. Based on Furness (2015), the total gannet BDMPS regional baseline population for the spring migration period is estimated to be 248,385 individuals ( Table 11.9   Open ▸ ). Using the average baseline mortality rate of 0.151 ( Table 11.21   Open ▸ ), the estimated regional baseline mortality of gannets is 37,506 birds in the spring migration period. The additional predicted mortality of two gannets for the Developer Approach and Scoping Approach A would increase the baseline mortality rate by 0.005% ( Table 11.23   Open ▸ ).
  4. Applying the Scoping Approach B mortality rate 3%, it was calculated that the predicted theoretical additional mortality due to displacement effects was six gannets (three adults and three immature birds) in the spring migration period. The additional predicted mortality of six gannets for Scoping Approach B would increase the baseline mortality rate by 0.016% ( Table 11.24   Open ▸ ).
Assessment of Displacement Mortality throughout the Year
  1. Predicted gannet mortality as a result of displacement in the Proposed Development array area and 2 km buffer for all seasons as calculated above, was summed for the whole year.
  2. Based on an assumed displacement rate of 70% and the Developer Approach and Scoping Approach A mortality rate of 1%, the predicted theoretical annual additional mortality due to displacement effects was an estimated 44 gannets. This corresponds to an increase in the baseline mortality rate of 0.23% ( Table 11.23   Open ▸ ).
  3. Applying the Scoping Approach B displacement rate of 70% and mortality rate 3%, the predicted theoretical additional annual mortality due to displacement effects was an estimated 127 gannets. This corresponds to an increase in the baseline mortality rate of 0.66% ( Table 11.24   Open ▸ ).

Based on the results of the displacement assessment for the Developer Approach and Scoping Approaches A and B, the magnitude of impact from displacement on the regional gannet population was considered to be negligible, as the estimated increases in the annual baseline mortality rate were below 1%.

Summary of PVA Assessment
  1. Although these displacement mortality estimates did not suggest a potentially significant increase in the baseline mortality rate for gannet for either the Developer Approach or Scoping Approaches A or B, PVA analysis was conducted on the gannet regional SPA population. The PVA analysis was carried out considering a range of displacement and mortality rates as well as a range of collision scenarios. The PVA assessment for gannet is presented following the collision impact section of this chapter (see paragraph 456).
Sensitivity of the Receptor
  1. 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 gannet was one of the species which strongly or nearly completely avoided offshore wind farms (Dierschke et al., 2016). However, other factors such as flexibility of habitat use and extensive foraging range also should be considered. A review of vulnerability of Scottish seabirds to offshore wind turbines in the context of disturbance and displacement ranked gannet with a score of two, where five was the most vulnerable score and one was the least vulnerable (Furness and Wade, 2012), while a subsequent review ranked gannet with a score of three (Furness et al., 2013). Bradbury et al., (2014), classified the gannet population vulnerability to displacement from offshore wind farms as very low.
  2. However, it should be noted that the inclusion of gannets within the 2km buffer to determine the total number of birds subject to displacement is precautionary, since in reality the avoidance rate is likely to fall with increasing distance from the site, as demonstrated in a study of gannet distribution in relation to the Greater Gabbard wind farm (APEM, 2014).
  3. Based on analysis of breeding adult gannet tracking data from the Bass Rock presented in volume 3, appendix 11.4, annex E, it is considered that the majority of adult gannets passing through Proposed Development are in transit rather than actively foraging. In addition, this analysis demonstrates the large size of the home range in relation to the Proposed Development, together with the known wide range of prey species available to gannets foraging in the area. This, together with the evidence from reviews presented above and from post-construction studies summarised in volume 3, appendix 4, indicates that gannet sensitivity to displacement from operational offshore wind farms is likely to be medium ( Table 11.16   Open ▸ ).
  4. Estimated numbers of gannets recorded within the Proposed Development array area would qualify as nationally important in the breeding season (volume 3, appendix 11.1), with individuals potentially originating from a number of SPAs in the region. On this basis the conservation importance for gannet was considered to be medium.
Significance of the Effect
  1. For displacement effects on gannet from the Project alone, 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
  1. 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.

Kittiwake

  1. For the Developer Approach displacement assessment, a displacement rate of 30% and a mortality rate of 2% was applied for the breeding season based on an evaluation of the published literature and in line with values used previously for other Forth and Tay offshore wind farm displacement assessments. In addition, it was considered that no displacement mortality is likely to occur during the non-breeding season, therefore no displacement assessment was undertaken for the non-breeding season.
  2. There were two parts to the Scoping Approach displacement assessment and these are outlined below. For Scoping Approach A, a displacement rate of 30% and a mortality rate of 1% were applied for the breeding and non-breeding seasons. For Scoping Approach B, a displacement rate of 30% and a mortality rate of 3% were applied for the breeding and non-breeding seasons.
  3. 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
  1. Kittiwakes were most abundant in the Proposed Development array area and 2 km buffer in the breeding season, with peak estimates of 24,949 birds in April 2019 and 17,333 birds in August 2020, which gave a MSP of 21,141 birds in the breeding season. In the autumn migration period of the non-breeding season, peak estimates were 2,997 birds in September 2019 and 19,383 birds in September 2020, which gave a MSP of 11,190 birds over the period. In the spring migration period of the non-breeding season, peak estimates were 17,174 birds in March 2019 and 10,358 birds in April 2021, which gave a MSP of 13,766 birds over the period (see volume 3, appendix 11.4).
  2. 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.
  3. For the Developer Approach, annual estimated kittiwake mortality from displacement in the Proposed Development and a 2 km buffer is presented in Table 11.26   Open ▸ .
  4. For Scoping Approaches A and B, annual estimated kittiwake mortality from displacement in the Proposed Development and a 2 km buffer is presented in Table 11.27   Open ▸ and Table 11.28   Open ▸ . For both Developer and Scoping 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.
  5. 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 kittiwake, the adult baseline survival rate is estimated to be 0.855, therefore the corresponding rate for adult mortality is 0.145. 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 11.26:
Displacement Mortality Estimates for Kittiwake for the Proposed Development array area plus 2 km buffer in the breeding season for the Developer Approach

Table 11.26: Displacement Mortality Estimates for Kittiwake 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 2% in breeding season.

 

Table 11.27:
Displacement Mortality Estimates for Kittiwake for the Proposed Development array area plus 2 km buffer by bio-season for Scoping Approach A

Table 11.27: Displacement Mortality Estimates for Kittiwake 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 1% in breeding and non-breeding seasons.

 

Table 11.28:
Displacement Mortality Estimates for Kittiwake for the Proposed Development array area plus 2 km buffer by bio-season for Scoping Approach B

Table 11.28: Displacement Mortality Estimates for Kittiwake 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 3% in breeding and non-breeding seasons.

 

Breeding Season
  1. During the breeding season, the mean peak abundance for kittiwake is 21,141 individuals within the Proposed Development array area and 2 km buffer. When considering the Developer Approach and Scoping Approach displacement rate of 30% in the Proposed Development array area and 2 km buffer, this would affect an estimated 6,343 birds. However, this estimate includes non-breeding adults and immature birds, as well as breeding adults.
  2. 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 recorded on digital aerial baseline surveys in the Offshore Ornithology study area ( Table 11.29   Open ▸ ) (volume 3, appendix 11.1).

 

Table 11.29:
Proportions of Juvenile, Immature and Adult Kittiwakes Recorded on Digital Aerial Surveys

Table 11.29: Proportions of Juvenile, Immature and Adult Kittiwakes Recorded on Digital Aerial Surveys

 

  1. Based on the proportion of immature kittiwakes recorded on digital aerial baseline surveys in the breeding season, 3% of the population present are immature birds ( Table 11.29   Open ▸ ), Although this is likely to be an underestimate, since it is not possible to age all birds recorded on surveys, this would mean that an estimated 190 kittiwakes displaced from the Proposed Development array area and 2 km buffer during the breeding season would be immature birds, with 6,153 adult birds also displaced.
  2. Applying the Developer Approach mortality rate of 2%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 127 kittiwakes (123 adults and four 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 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, 12 adult kittiwakes were considered to be not breeding and so 111 adult breeding kittiwakes were taken forward for the breeding season assessment.
  3. The total kittiwake regional baseline breeding population is estimated to be 319,126 adult birds ( Table 11.9   Open ▸ ). The adult baseline survival rate for kittiwake is estimated to be 0.855 ( Table 11.21   Open ▸ ), which means that the corresponding rate for adult mortality is 0.145. Applying this mortality rate, the estimated regional baseline mortality of kittiwakes is 46,273 adults per breeding season. The additional predicted mortality of 111 breeding adult kittiwakes for the Developer Approach would increase the baseline mortality rate by 0.24% ( Table 11.26   Open ▸ ).
  4. Applying the Scoping Approach A mortality rate of 1%3%, the predicted theoretical additional mortality due to displacement effects was 64 (62 adults and two immature birds) kittiwakes in the breeding season. Accounting for 10% of adult kittiwakes being “sabbatical” birds, this total is revised to 56 breeding adult kittiwakes.
  5. The additional predicted mortality of 56 breeding adult kittiwakes would increase the baseline mortality rate by 0.12% ( Table 11.27   Open ▸ ).
  6. Applying the Scoping Approach B mortality rate of 3%, the predicted theoretical additional mortality due to displacement effects was 191 kittiwakes (185 adults and six immature birds) in the breeding season. Accounting for 10% of adult kittiwakes being “sabbatical” birds, this total is revised to 166 breeding adult kittiwakes.
  7. The additional predicted mortality of 166 breeding adult kittiwakes would increase the baseline mortality rate by 0.36% ( Table 11.28   Open ▸ ).
Non-breeding Season – Autumn Migration Period
  1. For the Developer Approach, kittiwake displacement was not considered for the autumn migration period of the non-breeding season, for the reasons outlined in Paragraph 215.
  2. For the autumn migration period of the non-breeding season, the mean peak abundance for kittiwake was 11,190 individuals within the Proposed Development array area and 2 km buffer. When considering the Scoping Approach displacement rate of 30% in the Proposed Development array area and 2 km buffer, this would affect an estimated 3,357 birds ( Table 11.27   Open ▸ ).
  3. Based on information presented in Furness (2015), in the non-breeding season 47% of the population present in the autumn migration period are immature birds and 53% of birds are adults. This would mean that an estimated 1,578 kittiwakes displaced from the Proposed Development array area and 2 km buffer during the autumn migration period would be immature birds, with 1,779 adult birds also displaced.
  4. Applying the Scoping Approach A mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 34 kittiwakes (26 adults and eight immature birds) in the autumn migration period. Based on Furness (2015), the total kittiwake BDMPS regional baseline population for the autumn migration period is estimated to be 829,937 individuals ( Table 11.9   Open ▸ ). Using the average baseline mortality rate of 0.160 ( Table 11.21   Open ▸ ), the estimated regional baseline mortality of kittiwakes is 132,790 birds in the autumn migration period of the non-breeding season. The additional predicted mortality of 34 kittiwakes for Scoping Approach A would increase the baseline mortality rate by 0.026% ( Table 11.27   Open ▸ ).
  5. Applying the Scoping Approach B mortality rate of 3%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 101 kittiwakes (77 adults and 24 immature birds) in the autumn migration period. Based on Furness (2015), the total kittiwake BDMPS regional baseline population for the autumn migration period is estimated to be 829,937 individuals ( Table 11.9   Open ▸ ). Using the average baseline mortality rate of 0.160 ( Table 11.21   Open ▸ ), the estimated regional baseline mortality of kittiwakes is 132,790 birds in the autumn migration period of the non-breeding season. The additional predicted mortality of 101 kittiwakes for Scoping Approach B would increase the baseline mortality rate by 0.076% ( Table 11.28   Open ▸ ).
Non-breeding Season – Spring Migration Period
  1. For the Developer Approach, kittiwake displacement was not considered for the spring migration period of the non-breeding season, for the reasons outlined in Paragraph 215.
  2. For the spring migration period of the non-breeding season, the mean peak abundance for kittiwake was 13,766 individuals within the Proposed Development array area and 2 km buffer. When considering the Scoping Approach displacement rate of 30% in the Proposed Development array area and 2 km buffer, this would affect an estimated 4,130 birds ( Table 11.27   Open ▸ ).
  3. Based on information presented in Furness (2015), in the non-breeding season, 47% of the population present in the spring migration period are immature birds, and 53% of birds are adults. This would mean that an estimated 1,941 kittiwakes displaced from the Proposed Development array area and 2 km buffer during the spring migration period would be immature birds, with 2,189 adult birds also displaced.
  4. Applying the Scoping Approach A mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 41 kittiwakes (34 adults and seven immature birds) in the spring migration period. Based on Furness (2015), the total kittiwake BDMPS regional baseline population for the spring migration period is estimated to be 627,816 individuals ( Table 11.9   Open ▸ ). Using the average baseline mortality rate of 0.160 ( Table 11.21   Open ▸ ), the estimated regional baseline mortality of kittiwakes is 100,451 birds in the spring migration period. The additional predicted mortality of 41 kittiwakes for Scoping Approach A would increase the baseline mortality rate by 0.041% ( Table 11.27   Open ▸ ).
  5. Applying the Scoping Approach B mortality rate of 3%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 124 kittiwakes (104 adults and 20 immature birds) in the spring migration period. Based on Furness (2015), the total kittiwake BDMPS regional baseline population for the spring migration period is estimated to be 627,816 individuals ( Table 11.9   Open ▸ ). Using the average baseline mortality rate of 0.160 ( Table 11.21   Open ▸ ), the estimated regional baseline mortality of kittiwakes is 100,451 birds in the spring migration period. The additional predicted mortality of 124 kittiwakes for Scoping Approach B would increase the baseline mortality rate by 0.123% ( Table 11.28   Open ▸ ).
Assessment of Displacement Mortality throughout the Year
  1. Predicted kittiwake mortality as a result of displacement in the Proposed Development array area and 2 km buffer for all seasons as calculated above, was summed for the whole year.
  2. Based on an assumed displacement rate of 30% and the Developer Approach mortality rate of 2%, the predicted theoretical additional mortality due to displacement effects was an estimated 111 breeding adult kittiwakes in the breeding season only. This corresponds to an increase in the baseline mortality rate of 0.24% ( Table 11.26   Open ▸ ).
  3. Applying the Scoping Approach A displacement rate of 30% and mortality rate of 1% in the breeding and non-breeding seasons, the predicted theoretical additional annual mortality due to displacement effects was an estimated 131 kittiwakes. This corresponds to an increase in the baseline mortality rate of 0.19% ( Table 11.27   Open ▸ ).
  4. Applying the Scoping Approach B displacement rate of 30% and mortality rate of 3% in the breeding and non-breeding seasons, the predicted theoretical additional annual mortality due to displacement effects was an estimated 391 kittiwakes. This corresponds to an increase in the baseline mortality rate of 0.56% ( Table 11.28   Open ▸ ).
  5. Based on the results from the displacement assessment for the Developer Approach and the Scoping Approaches A and B, the magnitude of impact from displacement on the regional kittiwake population was considered to be negligible, as the estimated increases in the annual baseline mortality rate for kittiwake were below 1%.
Summary of PVA Assessment
  1. Although these displacement mortality estimates did not suggest a potentially significant increase in the baseline mortality rate for kittiwake for either the Developer Approach or Scoping Approaches A and B, PVA analysis was conducted on the kittiwake regional SPA population. The regional PVA analysis was carried out considering a range of displacement and mortality rates as well as a range of collision scenarios. The regional PVA assessment for kittiwake is presented following the collision impact section of this chapter (see paragraph 548).
Sensitivity of the Receptor
  1. For kittiwake, there is evidence from other operating offshore wind farm projects that displacement is not likely to occur to any significant level. A review of post-construction studies of seabirds at offshore wind farms in European waters concluded that kittiwake was one of the species which were hardly affected by offshore wind farms or with attraction and avoidance approximately equal over all studies (Dierschke et al., 2016). Two reviews of vulnerability of Scottish seabirds to offshore wind turbines in the context of disturbance and displacement ranked kittiwake with a score of two, where five was the most vulnerable score and one was the least vulnerable (Furness and Wade, 2012, Furness et al., 2013). Similarly, Bradbury et al., (2014), classified the kittiwake population vulnerability to displacement as very low.
  2. On the basis of evidence from reviews presented above and from post-construction studies summarised in volume 3, appendix 4, it is considered that kittiwake has low sensitivity to (high tolerance of) offshore wind farms ( Table 11.16   Open ▸ ).
  3. Estimated numbers of kittiwakes recorded within the Proposed Development array area would qualify as nationally important in the breeding season (See volume 3, appendix 11.1, annex G), with individuals likely originating from a number of SPAs and non-SPAs in the region. On this basis the conservation importance for kittiwake was considered to be medium.
Significance of the Effect
  1. For displacement effects on kittiwake from the Project alone, for both the Developer Approach and Scoping Approaches A and B, the magnitude of the impact is deemed to be negligible, and the sensitivity of the receptor is considered to be low. 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
  1. 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.

Guillemot

  1. 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.
  2. 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.
  3. 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
  1. Guillemots were the most abundant species recorded in the Offshore Ornithology study area during the aerial survey programme, with birds recorded most frequently between April and May and August and/or September in both years, coinciding with the start of the breeding season and the post-breeding flightless moult stage respectively.
  2. Guillemots were most abundant in the Proposed Development array area and 2 km buffer in the breeding season with peak estimates of 94,806 birds in April 2019 and 53,499 birds in June 2020, which gave a MSP of 74,154 birds in the breeding season.
  3. Overall, within the Offshore Ornithology study area, the peak population estimate occurred in April 2021, with an estimated 242,168 birds (95%CI 190,509 – 305,941) recorded (See volume 3, appendix 11.1). The regional breeding population of guillemots is currently estimated to be 353,971 birds (volume 3, 11.1), therefore the estimated population in the Offshore Ornithology study area for April 2021 would be the equivalent of 68.4% of the regional breeding population, which is considered unlikely to be the case. It is likely that many of these birds are from other breeding colonies further north, for example Shetland or Norway, and that these birds are passing through the Offshore Ornithology study area on the way to these colonies.
  4. As previously noted in paragraph 48, the high estimated number of guillemots recorded in April 2021 was used to represent April 2019, as no surveys were possible in that month due to unsuitable weather conditions. This high number was therefore taken through the MSP calculations, resulting in a higher estimated number of displaced guillemots for the 2019 breeding season. This will also have inflated the predicted number of guillemot mortalities arising from displacement in the 2019 breeding season, and this should be borne in mind when looking at the assessment outputs.
  5. In the non-breeding season, peak estimates were 44,146 birds in March 2020 and 44,194 birds in September 2020, which gave a MSP of 44,171 birds over the period (see volume 3, appendix 11.4).
  6. 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.
  7. For the Developer Approach, annual estimated guillemot mortality from displacement in the Proposed Development array area and 2 km buffer is presented in Table 11.30   Open ▸ .
  8. For the Scoping Approach, annual estimated guillemot mortality from displacement in the Proposed Development array area and 2 km buffer is presented in Table 11.31   Open ▸ and Table 11.32   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.
  9. 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 guillemot, the adult baseline survival rate is estimated to be 0.927, therefore the corresponding rate for adult mortality is 0.073. 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 11.30:
Displacement Mortality Estimates for Guillemot for the Proposed Development array area plus 2 km buffer by bio-season for the Developer Approach

Table 11.30: Displacement Mortality Estimates for Guillemot 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 11.31:
Displacement Mortality Estimates for Guillemot for the Proposed Development array area plus 2 km buffer by bio-season for Scoping Approach A

Table 11.31: Displacement Mortality Estimates for Guillemot 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 11.32:
Displacement Mortality Estimates for Guillemot for the Proposed Development array area plus 2 km buffer by bio-season for Scoping Approach B

Table 11.32: Displacement Mortality Estimates for Guillemot 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
  1. During the breeding season, the mean peak abundance for guillemot is 74,154 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 37,077 birds. However, this estimate includes non-breeding adults and immature birds, as well as breeding adults.
  2. 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 11.33   Open ▸ ) (volume 3, appendix 11.6).

 

Table 11.33:
PVA Stable Age Structure for Guillemots

Table 11.33: PVA Stable Age Structure for Guillemots

 

  1. Based on the proportion of immature guillemots from the stable age structure ( Table 11.33   Open ▸ ), 48.8% of the population present are immature birds, then this would mean that an estimated 18,094 guillemots displaced from the Proposed Development array area and 2 km buffer during the breeding season would be immature birds, with 18,983 adult birds also displaced.
  2. Applying the Developer Approach mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 371 guillemots (190 adults and 181 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 guillemots 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, 13 adult guillemots were considered to be not breeding and so 177 adult breeding guillemots were taken forward for the breeding season assessment.
  3. The total guillemot regional baseline breeding population is estimated to be 353,971 individuals ( Table 11.9   Open ▸ ). The adult baseline survival rate for guillemot is estimated to be 0.927 ( Table 11.21   Open ▸ ), which means that the corresponding rate for adult mortality is 0.073. Applying this mortality rate, the estimated regional baseline mortality of guillemots is 25,840 adult breeding birds per breeding season. The additional predicted mortality of 177 adult breeding guillemots would increase the baseline mortality rate by 0.68% ( Table 11.30   Open ▸ ).
  4. When considering the Scoping Approach displacement rate of 60% in the Proposed Development array area and 2 km buffer, this would affect an estimated 44,493 birds ( Table 11.31   Open ▸ and Table 11.32   Open ▸ ). Assuming that 48.8% of the population present are immature birds ( Table 11.33   Open ▸ ), then this would mean that an estimated 21,713 guillemots displaced from the Proposed Development array area and 2 km buffer during the breeding season would be immature birds, with 22,780 adult birds also displaced.
  5. Applying the Scoping Approach A mortality rate of 3% in the breeding season, it was calculated that the predicted theoretical additional mortality due to displacement effects was 1,335 guillemots (684 adults and 651 immature birds) in the breeding season. As above, a sabbatical rate of 7% for non-breeding adult guillemots (volume 3, appendix 11.6) has been applied for this assessment. This resulted in 48 adult guillemots being considered to be not breeding and so 636 adult breeding guillemots were taken forward for the breeding season assessment.
  6. Applying a mortality rate for adult guillemots of 0.073, the estimated regional baseline mortality of guillemots is 25,840 adult breeding birds per breeding season. The additional predicted mortality of 636 breeding adult guillemots would increase the baseline mortality rate by 2.5% ( Table 11.31   Open ▸ ).
  7. Applying the Scoping Approach B mortality rate of 5% in the breeding season, it was calculated that the predicted theoretical additional mortality due to displacement effects was 2,225 guillemots (1,139 adults and 1,086 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 guillemots (volume 3, appendix 11.6), resulted in 80 adult guillemots being considered to be not breeding and so 1,059 adult breeding guillemots were taken forward for the breeding season assessment.
  8. Applying a mortality rate for adult guillemots of 0.073, the estimated regional baseline mortality of guillemots is 25,840 adult breeding birds per breeding season. The additional predicted mortality of 1,059 breeding adult guillemots would increase the baseline mortality rate by 4.1% ( Table 11.32   Open ▸ ).
Non-Breeding Season
  1. During the non-breeding season, the mean peak abundance for guillemot is 44,171 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 22,086 birds ( Table 11.30   Open ▸ ).
  2. Based on the proportion of immature guillemots from the stable age structure ( Table 11.33   Open ▸ ), 48.8% of the population present are immature birds. This would mean that an estimated 10,778 guillemots displaced from the Proposed Development array area and 2 km buffer during the non-breeding season would be immature birds, with 11,308 adult birds also displaced.
  3. Applying the Developer Approach mortality rate of 1%, it was calculated that the predicted theoretical additional mortality due to displacement effects was 221 guillemots (113 adults and 108 immature birds) in the non-breeding season. Scoping Opinion advice for guillemots was to use the regional breeding population within mean maximum foraging range +1S.D. as the reference population for the guillemot non-breeding season, on the basis that birds do not travel far from their breeding colonies in the non-breeding season (Buckingham et al. 2022). Therefore, the total guillemot regional baseline population in the non-breeding season, including breeding adults and immature birds, is estimated to be 353,971 individuals.
  4. Using the average baseline mortality rate of 0.148 ( Table 11.21   Open ▸ ), the estimated regional baseline mortality of guillemots is 52,388 birds per non-breeding season. The additional predicted mortality of 221 guillemots would increase the baseline mortality rate by 0.42% ( Table 11.30   Open ▸ ).
  5. When considering the Scoping Approach displacement rate of 60% in the Proposed Development array area and 2 km buffer, this would affect an estimated 26,503 birds ( Table 11.30   Open ▸ ). Assuming that 48.8% of the population present are immature birds ( Table 11.33   Open ▸ ), then this would mean that an estimated 12,933 guillemots displaced from the Proposed Development array area and 2 km buffer during the non-breeding season would be immature birds, with 13,570 adult birds also displaced.
  6. Applying the Scoping Approach A mortality rate of 1% for the non-breeding season, it was calculated that the predicted theoretical additional mortality due to displacement effects was 266 guillemots (136 adults and 130 immature birds) in the non-breeding season.
  7. As outlined above, Scoping Opinion advice for guillemots was to use the regional breeding population within mean maximum foraging range +1S.D. as the reference population for the guillemot non-breeding season, therefore the total guillemot regional baseline population for the non-breeding season is estimated to be 353,971 individuals. Using the average baseline mortality rate of 0.148 ( Table 11.21   Open ▸ ), the estimated regional baseline mortality of guillemots is 52,388 birds per non-breeding season. The additional predicted mortality of 266 guillemots would increase the baseline mortality rate by 0.51% ( Table 11.31   Open ▸ ).
  8. Applying the Scoping Approach B mortality rate of 3% for the non-breeding season, it was calculated that the predicted theoretical additional mortality due to displacement effects was 796 guillemots (408 adults and 388 immature birds) in the non-breeding season.
  9. As outlined above, Scoping Opinion advice for guillemots was to use the regional breeding population within mean maximum foraging range +1S.D. as the reference population for the guillemot non-breeding season, therefore the total guillemot regional baseline population for the non-breeding season is estimated to be 353,971 individuals. Using the average baseline mortality rate of 0.148 ( Table 11.21   Open ▸ ), the estimated regional baseline mortality of guillemots is 52,388 birds per non-breeding season. The additional predicted mortality of 796 guillemots would increase the baseline mortality rate by 1.52% ( Table 11.32   Open ▸ ).
Assessment of Displacement Mortality throughout the Year
  1. Predicted guillemot mortality as a result of displacement in the Proposed Development array area and 2 km buffer for all seasons as calculated above, was summed for the whole year.
  2. Based on the Developer Approach displacement rate of 50% and a mortality rate of 1% throughout the year, the predicted theoretical additional annual mortality due to displacement effects was an estimated 398 guillemots. This corresponds to an increase in the baseline mortality rate of 1.1% ( Table 11.30   Open ▸ ).
  3. 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 mortality due to displacement effects was an estimated 902 guillemots. This corresponds to an increase in the baseline mortality rate of 3.01% ( Table 11.31   Open ▸ ).
  4. 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 mortality due to displacement effects was an estimated 1,855 guillemots. This corresponds to an increase in the baseline mortality rate of 5.62% ( Table 11.32   Open ▸ ).
  5. These displacement mortality estimates suggest a potential significant increase in the baseline mortality rate for guillemot therefore PVA analysis was conducted on the guillemot regional SPA population.