Collision risk - operation and maintenance
  1. As for displacement, breeding season collision estimates attributed to the Fowlsheugh SPA kittiwake population were extracted from the existing assessments for offshore wind farms that are in planning, consented, under construction or in operation (annex E of Offshore EIA Report, volume 3, appendix 11.6). Kittiwake collision estimates for the non-breeding periods were derived from the information collated in the East Anglia TWO and East Anglia ONE North submissions (MacArthur Green and Royal HaskoningDHV 2021), with the collision numbers for some projects updated using more recent design information where required (annex D of Offshore EIA Report, volume 3, appendix 11.6). The non-breeding season collision estimates were apportioned to the Fowlsheugh SPA population according to the BDMPS approach (Furness 2015).
  2. Collision estimates based on consented and ‘as-built’11 designs were also considered but for the current SPA population this did not affect the collision estimates for the other Forth and Tay wind farms and had minimal effects on those for the other UK North Sea wind farms (with the respective totals differing by 3.6 adults, representing less than 4% of the estimates for the consented designs). Therefore, only the estimates for the consented designs are considered in this case.
  3. In contrast to the displacement estimates derived for the other projects, existing collision estimates for these projects were not adjusted to align with the Scoping Approach of using the maximum (rather than the mean) monthly estimate of the density of birds in flight (with all of the other projects likely to have followed the ‘standard’ approach of using the mean density). Such an adjustment would require the re-calculation of the CRMs for each project, which would not be feasible in many cases because of the difficulty in accessing the appropriate baseline data.
  4. As for displacement, the potential mortality estimates derived for the other projects were combined with those for the Proposed Development to give estimates for (i) the Proposed Development in-combination with the other Forth and Tay wind farms and (ii) the Proposed Development in-combination with the other UK North Sea wind farms according to both the Scoping Approach and Developer Approach (noting that for the Scoping Approach it is only the estimates for the Proposed Development that are calculated according to this approach) (Table 5.87).
Table 5.87:
Predicted Collision Effects on the Fowlsheugh SPA Kittiwake Population due to the Proposed Development In-Combination with other Projects in the Forth and Tay and in UK North Sea Waters. Estimates are Presented for both the Scoping Approach and Developer Approach.

Table 5.87: Predicted Collision Effects on the Fowlsheugh SPA Kittiwake Population due to the Proposed Development In-Combination with other Projects in the Forth and Tay and in UK North Sea Waters. Estimates are Presented for both the Scoping Approach and Developer Approach.

 

  1. The potential mortality resulting from the predicted collision effects associated with other plans and projects increases that predicted for the Proposed Development alone by approximately 41 – 59% for the other Forth and Tay wind farms in-combination scenario and by approximately 90 – 129% for the other UK North Sea wind farms in-combination scenario (with the greater increases associated with the Developer Approach in each case - Tables 5.84 and 5.87). The vast majority of the collision mortality predicted on the SPA population (i.e. approximately 70 – 90%) is again attributable to the breeding season effects (Table 5.87), with the breeding season effects essentially limited to the Proposed Development and the other Forth and Tay wind farms (see annex D of Offshore EIA Report, volume 3, appendix 11.6).
  2. For the Proposed Development in-combination with the other Forth and Tay wind farms, the additional annual mortality of adult kittiwakes from the Fowlsheugh SPA population predicted due to collisions represents 0.40% of the current adult breeding population at this colony (i.e. 26,542 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and 0.51% of this population as determined by the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.145 – see Table 2.13 in volume 3, appendix 11.6of the Offshore EIA Report), the estimates of adult collision mortality equate to an increase of 2.8% for the Developer Approach and of 3.6% for the Scoping Approach.
  3. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult kittiwakes from the Fowlsheugh SPA population predicted due to collisions represents 0.54% of the current adult breeding population at this colony (i.e. 26,542 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and 0.66% of this population as determined by the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.145 – see Table 2.13 in volume 3, appendix 11.6 of the Offshore EIA Report), the estimates of adult collision mortality equate to an increase of 3.7% for the Developer Approach and of 4.5% for the Scoping Approach.
  4. The potential levels of impact on the Fowlsheugh SPA kittiwake population resulting from the mortality predicted from collisions associated with the Proposed Development in-combination with other wind farms in the Forth and Tay or in-combination with other wind farms in the UK North Sea during the operation and maintenance phase are considered in more detail below in the Effects In-Combination: Population-Level Impacts section. This presents the outputs from PVAs of the combined effects of predicted displacement and collision mortality on the SPA population.
In-combination: population-level impacts
  1. As for the Proposed Development alone, PVA was undertaken on the mortality to the adult and immature age classes predicted due to the combined displacement and collision effects associated with the Proposed Development in-combination with the other Forth and Tay wind farms and the Proposed Development in-combination with the other UK North Sea wind farms. This was on the basis of the potential mortality as determined by both the Scoping and Developer Approaches (see Tables 5.86 and 5.87 above).
  2. The approach to the PVA and the metrics used to summarise the PVA outputs are as described for the Proposed Development alone (see Project Alone: Population-Level Impacts section above).

 

Table 5.88:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Kittiwake Population Under Different Impact Scenarios for the Proposed Development In-Combination with the other Forth and Tay Wind Farms

Table 5.88: Projected 35 Year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Kittiwake Population Under Different Impact Scenarios for the Proposed Development In-Combination with the other Forth and Tay Wind Farms

 

Table 5.89:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Kittiwake Population Under Different Impact Scenarios for the Proposed Development in-Combination with the other UK North Sea Wind Farms.

Table 5.89: Projected 35 Year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Kittiwake Population Under Different Impact Scenarios for the Proposed Development in-Combination with the other UK North Sea Wind Farms.

 

  1. Given that the in-combination effects are inevitably greater than those for the Proposed Development alone, the PVA metrics for the Proposed Development in-combination with either the other Forth and Tay wind farms or the other UK North Sea wind farms suggest greater population-level impacts than as predicted for the Proposed Development alone (compare Table 5.88 and 5.89 with Table 5.85). Focussing on the outputs for the Proposed Development in-combination with the other UK North Sea wind farms, the CPS value for the Developer Approach indicates that the SPA population size would be reduced by almost 20% relative to the predicted population size under baseline conditions after 35 years, whilst the equivalent reduction for the Scoping Approach is 20 – 24% (Table 5.89). Reductions in the annual population growth rate (relative to that predicted under baseline conditions) are estimated to be 0.6% for the Developer Approach and 0.6 – 0.8% for the Scoping Approach. The values for the centile metric are estimated as 31.3 after 35 years for the Developer Approach and as 25.5 – 29.6 for the Scoping Approach, suggesting low to moderate levels of overlap in the distribution of the predicted impacted and un-impacted population sizes and, hence, a reasonable likelihood of the impacted population being smaller than the un-impacted population after 35 years. The PVA metrics for the Proposed Development in-combination with the other Forth and Tay wind farms indicate levels of impact which are midway between those for the Proposed Development alone and those for the UK North Sea in-combination scenario.
  2. The context within which the PVA metrics from these in-combination scenarios should be considered is outlined above in the Project Alone: Population-Level Impacts section for this SPA population.
In-combination: conclusion
  1. For both the Scoping and Developer Approaches, the predicted levels of impact associated with the two in-combination scenarios represent a marked increase compared to those associated with the Proposed Development alone. These levels of impact suggest the potential for the in-combination effects to lead to a marked reduction in the size of the Fowlsheugh SPA population after 35 years relative to that which would occur in the absence of these effects. The predicted levels of impact are such that for the Developer Approach (which predicts lower levels of impact than the Scoping Approach), this potential reduction in population size is 14% for the Proposed Development in-combination with the other Forth and Tay wind farms and almost 20% for the Proposed Development in-combination with the other UK North Sea wind farms.
  2. For the Proposed Development in-combination with the other Forth and Tay wind farms but not in-combination with the other UK North Sea wind farms), the centile values indicate a reasonable likelihood of the impacted population being similar in size to the un-impacted population after 35 years whilst the context that has been outlined above (in relation to (i) the high levels of precaution incorporated in the assessment and (ii) the likelihood that the effects from wind farm developments will be of minor importance relative to other management and environmental factors in determining the future status of the SPA kittiwake population) remains highly relevant. However, despite this, it is considered that the scale of the potential reduction in the size of the SPA population associated with the in-combination effects means that the possibility of an adverse effect on the SPA population cannot be excluded.
  3. Consequently, it is concluded that there is the potential for an adverse effect on the Fowlsheugh kittiwake population as a result of the predicted effects from (i) the Proposed Development in-combination with the other Forth and Tay wind farms and (ii) the Proposed Development in-combination with the other UK North Sea wind farms. This conclusion applies to the assessments undertaken according to both the Developer Approach and the Scoping Approach.

Assessment for the herring gull population

  1. The Fowlsheugh SPA herring gull population is currently estimated to number 707 breeding pairs, which is substantially below the citation population of 3,190 pairs (Offshore EIA Report, volume 3, appendix 11.5). As for the Fowlsheugh SPA kittiwakes, earlier estimates of the size of the SPA herring gull population are not readily available from Seabird Monitoring Database (SMP 2022) because the data from one of the four seabird count sectors which comprise the SPA are not fully aligned with the SPA boundary. Based upon the available data it seems clear that the SPA population size has been below the citation level since designation in 1992, and numbers were probably higher in the 1980s and early 1990s than currently (based upon counts from the ‘Tremuda/Old Hall Bay’ count sector of approximately 1000 AONs in 1986 and 1992 compared to 451 AONs in 2018). The more frequent count data from the Fowlsheugh RSPB reserve count sector also indicate an overall decline since the late 1980s, although numbers are lower and show some fluctuation.
  2. The Fowlsheugh SPA herring gull is considered to be in ‘unfavourable declining’ condition.
The potential for impacts on the herring gull population
  1. The Proposed Development and two kilometre buffer around the Proposed Development array area7 do not overlap with the Fowlsheugh SPA, so that potential impacts on its herring gull population will only occur as a result of individuals from the colony occurring in the area (or vicinity) of the Proposed Development. Consequently, the main focus of the assessment for this SPA is concerned with the Conservation Objective to maintain, in the long term, the population of the species as a viable component of the site because the other conservation objectives either apply to the site itself, and not to areas beyond the boundary, or are encompassed by the assessment of this first Conservation Objective (as for the maintain in the long term no significant disturbance of the species, because disturbance would only be considered significant if it caused an adverse effect on the population viability of the qualifying features).
  2. From published information on herring gull foraging ranges (Woodward et al. 2019), it is likely that during the breeding period herring gulls from the Fowlsheugh SPA occur within the area of the Proposed Development and of the two km buffer around the Proposed Development array. This is supported by the findings of the apportioning exercise, which estimates that 3.5% of the herring gulls occurring on the Proposed Development array area during the breeding season derive from this SPA colony (Offshore EIA Report, volume 3, appendix 11.5). The breeding period for herring gull is defined as April to August, following NatureScot (2020).
  3. In the non-breeding season, herring gulls in Great Britain are largely sedentary with relatively short local movements only (Wernham et al. 2002). However, there is an influx of breeding birds of Scandinavian breeding subspecies, L. argentatus argentatus (Coulson et al., 1984). On this basis,and following the scoping advice from NatureScot (volume 3, appendix 6.2 of the Offshore EIA Report), it is assumed that during the non-breeding period herring gulls remain largely within the waters in the region of the breeding colony, as defined by the mean maximum foraging range plus 1 SD (Woodward et al. 2019, Offshore EIA Report, volume 3, appendix 11.5). To account for the influx of birds from other regions to this regional population during the non-breeding period, the regional non-breeding population is assumed to increase (relative to the size of the breeding population) in accordance with the proportion of continental and western UK birds estimated to be present in the UK North Sea and Channel BDMPS (Furness 2015, Offshore EIA Report, volume 3, appendix 11.5).
  4. Given the above, there is potential for the Proposed Development to have effects on the Fowlsheugh SPA herring gull population during both the breeding and non-breeding periods.
Project alone: construction and decommissioning
Changes to prey availability
  1. Herring gulls have a highly opportunistic diet (del Hoyo et al., 1996), utilising terrestrial, intertidal and marine habitats to forage for a wide variety of prey species including invertebrates, small fish and carrion (including fishery discards). Indirect effects on herring gulls may arise as a result of changes in the availability, distribution, or abundance of these species during the construction and decommissioning phases of the Proposed Development. Reduction or disruption to prey availability may cause displacement from foraging grounds or reduced energy intake, affecting survival rates or productivity in the Fowlsheugh SPA herring gull population in the short-term.
  2. During construction there are a number of ways in which effects on herring gull prey species could occur, which are as outlined in the section on Project Alone: Construction and Decommissioning – Changes to prey availability for the St Abb’s Head to Fast Castle SPA kittiwake population. The Proposed Development array area encompasses 1,010 km2, whilst the Proposed Development export cable corridor encompasses 168 km2. Together these areas represent c. 10% of the total breeding season foraging area that is potentially available to the SPA herring gull population, as defined by the species’ mean-maximum breeding season foraging range plus 1 SD (i.e. 58.8±26.8 km; Woodward et al., 2019) and assuming that this range is represented by a semicircle to the seaward side of the colony. Furthermore, given their flexible foraging habits and the distance between the Proposed Development and the SPA, it is likely that the area of marine habitat encompassed by the Proposed Development is not of key importance for herring gulls breeding at the Fowlsheugh SPA. Non-breeding season effects are expected to similar since herring gulls in Great Britain do not disperse widely during winter (Wernham et al. 2002).
  3. During decommissioning, the effects from changes in prey availability are considered to be the same (or less) as for construction. It is currently unclear as to how the presence, and subsequent removal of, subsea structures may affect herring gull prey species (Birchenough and Degrae 2020; Scott, 2022). It is possible that prey abundance could decline from the levels present during the operation and maintenance period. This could occur if the sub-surface structures associated with the Proposed Development in the marine environment lead to an increase in key prey abundance within the Proposed Development array area and export cable corridor via the provision of artificial reef habitats. However, some infrastructure (such as scour and cable protection) is assumed to be left in situ with the impact of colonisation of infrastructure continuing in perpetuity following decommissioning. Thus, any reduction in prey abundance through removal of foundations is likely to be very small relative to the area over which breeding and non-breeding herring gulls forage.
  4. Given their wide-ranging foraging behaviour and plasticity in foraging habitat and diet (del Hoyo et al., 1996), together with any effects being intermittent, spatially-restricted and temporary in nature, it is considered that there is no potential for construction or decommissioning related changes in prey availability to lead to an adverse effect on the Fowlsheugh SPA herring population. This conclusion is consistent with the outcome of the EIA which concluded that effects from changes in prey availability on herring gulls during construction and decommissioning were not significant in EIA terms (volume 2, chapter 11 of the Offshore EIA Report).
Project alone: operation and maintenance
Collision risk
  1. Predictions of the number of herring gulls at risk from collisions due to the Proposed Development were calculated using the deterministic version of the SOSS offshore collision risk model (Band 2012, Offshore EIA Report, volume 3, appendix 11.3). Following the Scoping Opinion (volume 3, appendix 6.2 of the Offshore EIA Report), the assessment is based on the outputs from both options 2 and 3 of the CRM, which use the generic flight height data and for which option 2 assumes a uniform distribution of flight heights across the rotor swept zone and option 3 assumes the modelled flight height distribution (Band 2012, Johnston et al. 2014a,b). In accordance with the recommendations of the SNCBs (2014), and as advised by the Scoping Opinion, avoidance rates of 99.5% and 99.0% were applied to the outputs from option 2 and option 3, respectively.
  2. As outlined for the St Abb’s Head to Fast Castle SPA kittiwake population above, guidance on the use of the CRM suggests that model predictions should be based upon the mean monthly densities of flying birds estimated within the array area (Band 2012)8 and, to the best of the Applicant’s knowledge, this approach has been applied in all recent UK offshore wind farm assessments. Despite this, the Scoping Opinion advised that the CRMs for the Proposed Development should use the maximum monthly densities of flying birds within the array area. Further details on this are provided above in the Project Alone: Operation and Maintenance - Collision Risk section for the St Abb’s Head to Fast Castle SPA kittiwakes population and in Offshore EIA Report, volume 3, appendix 11.3 but, as a result of this overly precautionary approach (which does not follow previous precedent), the CRMs for herring gull were undertaken following:
  • The Scoping Approach of using the maximum monthly densities, and
  • The Developer Approach of using the mean monthly densities.
    1. In addition to the above, collision estimates for herring gulls were also calculated using options 2 and 3 of the stochastic version of the CRM (McGregor et al. 2018) with avoidance rates as derived from the bird collision-avoidance study undertaken at the Thanet offshore wind farm (Bowgen and Cook 2018). These additional collision estimates are not used as the basis of the assessments on the SPA herring gull populations but, instead, are used solely to illustrate the consequences of applying these alternative avoidance rates which have been derived from studies at an actual offshore wind farm. Details of these additional CRMs are provided in annex C of the Offshore EIA Report, volume 3, appendix 11.3.
    2. Herring gull collision estimates are calculated for the breeding and non-breeding periods, with estimates apportioned to the Fowlsheugh SPA population according to the NatureScot (2018) approach but with allowance made for the influx of birds from other regions during the non-breeding period (Offshore EIA Report, volume 3, appendix 11.5). The resulting estimates were apportioned to age classes according to the plumage characteristics of herring gulls recorded during the baseline surveys (Offshore EIA Report, volume 3, appendix 11.1), whilst on the basis of advice provided by NatureScot and Marine Scotland Science following Roadmap Meeting 4 (G. Holland, email 26/01/2022), it was also assumed that 35% of the breeding adults in the SPA population miss breeding in any given year (i.e. sabbatical birds) so that the number of adult collisions estimated during the breeding season was adjusted accordingly.
    3. Based upon option 2 of the deterministic CRM with a 99.5% avoidance rate applied, and in conjunction with the estimates and assumptions detailed above, the annual collision mortality of herring gulls from the Fowlsheugh SPA is predicted to be no more than a single adult bird (plus a small fraction of an immature bird) as determined by either the Scoping Approach or Developer Approach (Table 5.90). The vast majority of this mortality (i.e. over 80%) is predicted to occur during the breeding season. The collision estimates for option 3 of the deterministic CRM with a 99.0% avoidance rate applied (which was also recommended by the Scoping Opinion as a basis for the assessment) are not presented in Table 5.90 but give outputs that are approximately 40% lower than the option 2 estimates for both the Scoping and Developer Approaches (Offshore EIA Report, volume 3, appendix 11.3). In addition, the collision estimates produced using options 2 and 3 of the stochastic CRM with the Bowgen and Cook (2018) avoidance rates applied were similar to those obtained from option 3 of the deterministic CRM with the SNCB recommended 99.0% avoidance rate, and hence also substantially lower than those presented in Table 5.90 below (see annex C of the Offshore EIA Report, volume 3, appendix 11.3).

 

Table 5.90:
Predicted Collision Effects from the Proposed Development on the Fowlsheugh SPA Herring Gull Population, as Determined by the Scoping Approach and Developer Approach. Estimates are for the Maximum Design Scenario and are Based on Option 2 of the Deterministic CRM Using a 99.5% Avoidance Rate (see text)

Table 5.90: Predicted Collision Effects from the Proposed Development on the Fowlsheugh SPA Herring Gull Population, as Determined by the Scoping Approach and Developer Approach. Estimates are for the Maximum Design Scenario and are Based on Option 2 of the Deterministic CRM Using a 99.5% Avoidance Rate (see text)

 

  1. Based upon the estimates from option 2 of the CRM, the additional annual mortality of adult herring gulls from the Fowlsheugh SPA population predicted due to collisions with wind turbines in the Proposed Development array represents approximately 0.04% of the number of adults currently estimated to breed at this colony (i.e. 1,414 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach and approximately 0.07% as determined by the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.122 – see Table 2.11 in volume 3, appendix 11.6 of the Offshore EIA Report), the predicted adult collision mortality equates to increases of 0.3% and 0.6% for the Developer and Scoping Approaches, respectively.
  2. The potential levels of impact on the Fowlsheugh SPA herring gull population resulting from the predicted collision mortalities in Table 5.90 are considered in more detail below in the Project Alone: Population-Level Impacts section. This presents the outputs from PVAs of the potential effects of predicted collision mortality on the SPA population.
Changes to prey availability
  1. Potential impacts on key prey species for herring gulls breeding at the Fowlsheugh SPA during the operation and maintenance phase have been assessed in volume 2, chapter 9 of the Offshore EIA Report using the appropriate maximum design scenarios for these receptors. Reduction or disruption to prey availability through temporary and long-term subtidal habitat loss/disturbance, increased SSC and deposition, EMF from subsea electrical cabling, and colonisation of subsea structures could affect herring gull survival and productivity in the Fowlsheugh SPA population.
  2. Artificial structures introduced to the marine environment provide hard substrate for settlement of various organisms, which can increase local food availability for higher trophic levels. Whilst there is mounting evidence of potential benefits of artificial structures in marine environment (Birchenough and Degrae 2020), the statistical significance of such benefits and details about trophic interactions remain largely unknown (Scott, 2022).
  3. Given their wide-ranging foraging behaviour and plasticity in foraging habitat and diet (del Hoyo et al., 1996), together with any effects on prey during operation and maintenance being largely intermittent across a relatively small spatial extent, it is considered that there is no potential for operational or maintenance related changes in prey availability to lead to an adverse effect on the Fowlsheugh SPA herring gull population. This conclusion is consistent with the outcome of the EIA which concluded that effects from changes in prey availability on herring gulls during operation and maintenance were not significant in EIA terms (volume 2, chapter 11 of the Offshore EIA Report).
Project alone: population-level impacts
  1. As determined above, the effects from the Proposed Development alone which could lead to an adverse effect on the Fowlsheugh SPA herring gull population are limited to collision mortality during the operation and maintenance phase. For other effect pathways, there is considered to be no potential for an adverse effect on this population as a result of the Proposed Development alone, with any such effects likely to be small and of little, or no, consequence in terms of impacts at the population level.
  2. Given this, PVA was undertaken on the mortality to the adult and immature age classes predicted due to the collisions associated with the Proposed Development, as determined by both the Scoping and Developer Approaches (see Table 5.90 above). This was undertaken using the outputs from option 2 of the deterministic CRM with a 99.5% avoidance rate applied, as presented in Table 5.90 (noting that these are the more precautionary of the outputs from the different CRM approaches recommended by the Scoping Opinion). The population model for the SPA population was a stochastic, density independent, matrix model, based upon the demographic parameters specified in Table 2.11 of volume 3, appendix 11.6 of the Offshore EIA Report. The starting population size was the 2018 count for the SPA, with the projected population trends considered over a 35 year timescale (volume 3, appendix 11.5). The approach and methods to undertaking the PVA are as described in the section on Project Alone: Population-Level Impacts for the St Abb’s Head to Fast Castle kittiwake above (with further details provided in the Offshore EIA Report, volume 3, appendix 11.6).
  3. Outputs from the PVA are summarised according to the median predicted population-sizes at the end of the projection period, and the three metrics which the Scoping Opinion (volume 3, appendix 6.2 of the Offshore EIA Report) advised should be used for the interpretation of outputs and which have been shown to have relatively low sensitivity to factors such as varying population status and the mis-specification of the demographic rates underpinning the population model (Cook and Robinson 2015, Jitlal et al., 2017). These metrics are:
  • The CPS – the median of the ratio of the end-point size of the impacted to un-impacted (or baseline) population, expressed as a proportion;
  • The CPGR - the median of the ratio of the annual growth rate of the impacted to un-impacted population, expressed as a proportion; and
  • The centile of the un-impacted population that matches the median (i.e. 50th centile) of the impacted population (based upon the distribution of the end-point population-sizes generated by the multiple replications of the model runs, the value should always be less than 50 because the median for the impacted population is not expected to exceed that for the un-impacted population).

 

Table 5.91:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Herring Gull Population Under Different Impact Scenarios for the Proposed Development Alone

Table 5.91: Projected 35 Year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Herring Gull Population Under Different Impact Scenarios for the Proposed Development Alone

 

  1. The PVA predicted that the Fowlsheugh SPA herring gull population would increase strongly over the 35 year projection period irrespective of the effects from the Proposed Development. Thus, the population is predicted to be more than 10 times larger than the current estimate of 1,414 adult birds under all scenarios, including the baseline which assumes no wind farm effects (Table 5.91). Although the predicted increases in population size are inevitably greatest for the baseline scenario (because the PVAs are based on density independent models, which assume all mortality from the wind farm effects is additive and that there are no compensatory mechanisms operating within the population), the differences with the two impact scenarios are small. The predicted levels of increase are unlikely to occur in reality (and are, in part, a consequence of the absence of any compensatory density dependence within the models – as discussed in the section on Project Alone: Population-level impacts for the St Abb’s Head to Fast Castle SPA kittiwake population), whilst it is also notable that the predicted increase does not concur with the long-term documented status of this population (which remains well below the citation level and has likely been declining since the late 1980s – see above).
  2. The predicted population-level impacts are small, irrespective of whether these are determined using the Developer or Scoping Approaches. Thus, the CPS values indicate that the collision mortality associated with the Proposed Development alone would result in a reduction of less than 2% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects (Table 5.91). The associated reductions in annual population growth rate (relative to that predicted under baseline conditions) are not detectable (at least when the CPGR value is expressed to three decimal places) and the centile values are above 47.0, indicating considerable overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a high likelihood of the impacted population being of a similar size to the un-impacted population after 35 years. Furthermore, it should be noted that these predicted levels of impact are derived from the more precautionary of the two CRM approaches recommended by the Scoping Opinion, with the alternative approach giving collision estimates that are 40% lower than those used for the PVA.
Project alone: conclusion
  1. For both the Developer and Scoping Approaches, the potential effects from the Proposed Development alone on the Fowlsheugh SPA herring gull population are predicted to be small, with the resultant population-level impacts also predicted to be small. In addition, the PVA metrics indicate a high chance of the population being of a similar size to that which would occur in the absence of the Proposed Development after 35 years. Given this, it is concluded that the effects from the Proposed Development alone would not result in an adverse effect on this population
Effects in-combination
Effects of relevance to the in-combination assessment
  1. As detailed above, any effects from the Proposed Development alone on the Fowlsheugh SPA herring gull population during construction and decommissioning and resulting from changes to prey availability during operation and maintenance will be small and highly localised. As such, there is considered to be no potential for these effect pathways to add to impacts at the population-level that might result from other effects pathways associated with the Proposed Development or from the effects due to other plans and projects.
  2. Therefore, the potential for effects of the Proposed Development to act on the Fowlsheugh SPA herring gull population in-combination with other plans and projects is limited to the collision risk effect pathway during operation and maintenance. Following advice from NatureScot provided through the Ornithology Roadmap process (at meeting 3, 8th December 2021), the following sections consider these potential effects for (i) the Proposed Development in-combination with the other Forth and Tay wind farms and (ii) the Proposed Development in-combination with the other UK North Sea wind farms (noting that scenario (ii) includes those plans and projects which comprise scenario (i)).
Collision risk - operation and maintenance
  1. Breeding and non-breeding season collision estimates attributed to the Fowlsheugh SPA herring gull population were extracted from the existing assessments for offshore wind farms that are in planning, consented, under construction or in operation (annex E of Offshore EIA Report, volume 3, appendix 11.6). As for the Proposed Development, the non-breeding season collision estimates for the other plans and projects were adjusted to account for the influx of birds from other regions to this regional population during the non-breeding period, in accordance with the estimates used for the UK North Sea and Channel BDMPS (see above, Offshore EIA Report, volume 3, appendix 11.5, Furness 2015).
  2. The collision estimates derived for the other plans and projects were combined with those for the Proposed Development to give in-combination estimates for both the Forth and Tay wind farms and the UK North Sea wind farms according to both the Scoping Approach and Developer Approach. The two in-combination scenarios differed due to the inclusion of collision estimates from the Aberdeen and Kincardine wind farms within the UK North Sea (but not the Forth and Tay) scenario. Options based on consented and ‘as-built’12 designs did not affect the collision estimates from the other plans and projects, so that estimates are reported for the consented designs only. The collision estimates used for the Proposed Development are those presented in Table 5.90, which derived from the more precautionary of the two different CRM approaches recommended by the Scoping Opinion (see above).
  3. The existing collision estimates for the other plans and projects were not adjusted to align with the Scoping Approach of using the maximum (rather than the mean) monthly estimate of the density of birds in flight (with all of the other projects included with the in-combination scenario having followed the ‘standard’ approach of using the mean density). As explained for St Abb’s Head to Fast Castle SPA kittiwake above, such an adjustment would require the re-calculation of the CRMs for each project, which would not be feasible in many cases because of the difficulty in accessing the appropriate baseline data. Thus, it is only the estimates for the Proposed Development which differentiate the Developer and Scoping Approaches for the in-combination scenarios that are presented below.

 

Table 5.92:
Predicted Collision Effects on the Fowlsheugh SPA Herring Gull Population Due to the Proposed Development In-Combination with Other Projects in the Forth and Tay and in UK North Sea Waters. Estimates are Presented for both the Scoping Approach and Developer Approach

Table 5.92: Predicted Collision Effects on the Fowlsheugh SPA Herring Gull Population Due to the Proposed Development In-Combination with Other Projects in the Forth and Tay and in UK North Sea Waters. Estimates are Presented for both the Scoping Approach and Developer Approach

 

  1. Incorporating the potential mortality resulting from the predicted collision effects associated with other Forth and Tay wind farms increases the predicted annual collision mortality of adult birds by approximately one and half times compared to the Proposed Development alone for both the Developer and Scoping Approaches (with the increase slightly greater for the Developer Approach - Tables 5.90 and 5.92). Incorporating the predicted collision effects from the other UK North Sea wind farms results in an approximate fivefold and threefold increase compared to the Proposed Development alone for the Developer and Scoping Approaches, respectively. The increase in the predicted collision mortality amongst the immature age class when compared to the Proposed Development alone is of a similar extent, with the level of mortality predicted amongst this age class continuing to be smaller than that predicted amongst adult birds.
  2. For the Proposed Development in-combination with the other Forth and Tay wind farms, the additional annual mortality of adult herring gull from the Fowlsheugh SPA population predicted due to collisions represents 0.07% of the current adult breeding population at this colony (i.e. 1,414 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and 0.11% of this population as determined by the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.122 – see Table 2.11 in volume 3, appendix 11.6 of the Offshore EIA Report), the estimates of adult collision mortality equate to an increase of 0.6% for the Developer Approach and of 0.9% for the Scoping Approach.
  3. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult herring gull from the Fowlsheugh SPA population predicted due to collisions represents 0.21% of the current adult breeding population at this colony (i.e. 1,414 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and 0.23% of this population as determined by the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (which is based on applying a mortality rate of 0.122 – see Table 2.11 in volume 3, appendix 11.6 of the Offshore EIA Report), the estimates of adult collision mortality equate to an increase of 1.7% for the Developer Approach and of 1.9% for the Scoping Approach.
  4. The potential levels of impact on the Fowlsheugh SPA herring gull population resulting from the predicted collision mortalities in Table 5.92 are considered in more detail below in the In-Combination: Population-Level Impacts section. This presents the outputs from PVAs of the potential effects of predicted collision mortality on the SPA population.
In-combination: population-level impacts
  1. As for the Proposed Development alone, PVA was undertaken on the mortality to the adult and immature age classes predicted due to the collision effects associated with the Proposed Development in-combination with the other Forth and Tay wind farms and the Proposed Development in-combination with the other UK North Sea wind farms. This was on the basis of the potential mortality as determined by both the Scoping and Developer Approaches (see Table 5.92 above).
  2. The approach to the PVA and the metrics used to summarise the PVA outputs are as described for the Proposed Development alone (see Project Alone: Population-Level Impacts section above).

 

Table 5.93:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Herring Gull Population Under Different Impact Scenarios for the Proposed Development In-Combination with the other Forth and Tay Wind Farms

Table 5.93: Projected 35 Year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Herring Gull Population Under Different Impact Scenarios for the Proposed Development In-Combination with the other Forth and Tay Wind Farms

 

Table 5.94:
Projected 35 Year Population Sizes And Associated PVA Metrics for the Fowlsheugh SPA Herring Gull Population Under Different Impact Scenarios for the Proposed Development In-Combination with the other UK North Sea Wind Farms

Table 5.94: Projected 35 Year Population Sizes And Associated PVA Metrics for the Fowlsheugh SPA Herring Gull Population Under Different Impact Scenarios for the Proposed Development In-Combination with the other UK North Sea Wind Farms

 

  1. Given that the in-combination effects are inevitably greater than those for the Proposed Development alone, the PVA metrics for the Proposed Development in-combination with either the other Forth and Tay wind farms or the other UK North Sea wind farms suggest greater population-level impacts than as predicted for the Proposed Development alone (compare Table 5.93 and 5.94 with Table 5.91). However, whilst the levels of impact are clearly greater than for the Proposed Development alone, they remain relatively small. Focussing on the outputs for the Proposed Development in-combination with the other UK North Sea wind farms, the CPS values indicate that the SPA population size would be reduced by approximately 5% relative to the predicted population size under baseline conditions after 35 years, as determined by both the Scoping and Developer Approaches (Table 5.94). Reductions in the annual population growth rate (relative to that predicted under baseline conditions) are estimated to be 0.2% or less, whilst the centile values remain above 40, suggesting considerable levels of overlap in the distribution of the predicted impacted and un-impacted population sizes and, hence, a high likelihood of the impacted population being similar in size to the un-impacted population after 35 years. The PVA metrics for the Proposed Development in-combination with the other Forth and Tay wind farms indicate lower levels of impact, being intermediate between those for the Proposed Development alone and the Proposed Development in-combination with the other UK North Sea wind farms.
  2. It is also the case that these predicted levels of impact are derived using the more precautionary of the two CRM approaches recommended by the Scoping Opinion for the Proposed Development. Reliance on the alternative approach would result in a noticeable reduction in the predicted levels of impact, particularly for the Scoping Approach (for which the contribution of the Proposed Development to the in-combination effects is greatest).
In-combination: conclusion
  1. On the basis of the above considerations, it is concluded that the population-level impacts resulting from the Proposed Development in-combination with either the other Forth and Tay wind farms or the other UK North Sea wind farms would not produce an adverse effect on the Fowlsheugh SPA herring gull population. This conclusion applies irrespective of whether effects are determined according to the Scoping Approach or the Developer Approach.

Assessment for the guillemot population

  1. The Fowlsheugh SPA guillemot population is currently estimated to number 91,358 breeding individuals, which is substantially above the citation population size of 56,450 individuals (Offshore EIA Report, volume 3, appendix 11.5). As for the Fowlsheugh SPA kittiwakes, earlier estimates of the size of the SPA guillemot population are not readily available from Seabird Monitoring Database (Seabird Monitoring Programme | JNCC (bto.org)) because the data from one of the four seabird count sectors which comprise the SPA are not fully aligned with the SPA boundary. However, it is apparent from the available data that the Fowlsheugh RSPB reserve has held at least 90% of the SPA population in all three years for which data are available from all four of the SPA count sectors (i.e. 1986, 1999 and 2018).
  2. Based on the counts from the Fowlsheugh RSPB reserve, it is apparent that the SPA guillemot population has shown relative stability since the SPA was designated in 1992, with the counts from the Fowlsheugh RSPB reserve (which likely comprises approximately 90%, or slightly more, of the SPA population) being above the citation level in all years for which data are available (Figure 5.25).

Figure 525:
Guillemot Population Trend at the Fowlsheugh RSPB Reserve Between 1986 and 2018 (Noting that this Site Likely Accounts For Approximately 90% Of The SPA Population – see text). The Red Line Shows the Citation Population Size for the SPA (56,450 Individuals13). Data are from the Seabird Monitoring Programme Database (Seabird Monitoring Programme | JNCC (bto.org))

Figure 525: Guillemot Population Trend at the Fowlsheugh RSPB Reserve Between 1986 and 2018 (Noting that this Site Likely Accounts For Approximately 90% Of The SPA Population – see text). The Red Line Shows the Citation Population Size for the SPA (56,450 Individuals13). Data are from the Seabird Monitoring Programme Database (Seabird Monitoring Programme | JNCC (bto.org))

 

The potential for impacts on the guillemot population
  1. The Proposed Development and two kilometre buffer around the Proposed Development array area7 do not overlap with the Fowlsheugh SPA, so that potential impacts on its guillemot population will only occur as a result of individuals from the colony occurring in the area (or vicinity) of the Proposed Development. Consequently, the main focus of the assessment for this SPA population is concerned with the Conservation Objective to maintain, in the long term, the population of the species as a viable component of the site because the other conservation objectives either apply to the site itself, and not to areas beyond the boundary, or are encompassed by the assessment of this first Conservation Objective (as for the maintain in the long term no significant disturbance of the species, because disturbance would only be considered significant if it caused an adverse effect on the population viability of the qualifying features.
  2. From published information on guillemot foraging ranges generally (Woodward et al. 2019) and tracking from the SPA specifically (Wakefield et al. 2017), it is highly likely that during the breeding period guillemot from the Fowlsheugh SPA occur within the area of the Proposed Development and of the two km buffer around the Proposed Development array area. This is supported by the findings of the apportioning exercise, which estimates that approximately 36% of the guillemot occurring on the Proposed Development array area during the breeding season derive from this SPA colony (Offshore EIA Report, volume 3, appendix 11.5). The breeding period for guillemot is defined as April to mid-August, following the NatureScot (2020) guidance.
  3. Based on the NatureScot scoping advice (volume 3, appendix 6.2 of the Offshore EIA Report), during the non-breeding period guillemots are assumed to remain largely within the waters in the region of the breeding colony, as defined by the mean maximum foraging range plus 1 SD (Woodward et al. 2019, Buckingham et al. 2022, Offshore EIA Report, volume 3, appendix 11.5). Therefore, on this basis, the Proposed Development has a similar potential to have effects on the Fowlsheugh SPA guillemot population during the non-breeding period as during the breeding season, with 22% of the guillemots occurring on the Proposed Development array area during the non-breeding period estimated to derive from this SPA colony (Offshore EIA Report, volume 3, appendix 11.5).
Project alone: construction and decommissioning
Disturbance
  1. Direct disturbance to guillemots during the construction phase may arise within the Proposed Development array area (and its immediate vicinity) as a result of increased vessel movements and helicopter activity, as well as from other activities directly associated with the installation of the wind turbine foundations and other infrastructure, whilst there will also be increased vessel activity along the Proposed Development export cable corridor due to the cable laying activities. The levels of such activities that could arise are outlined in Table 4.1, with these activities occurring during construction campaigns within a construction period of at most eight years duration.
  2. A total of up to 11,482 vessel round trips may occur over the construction phase, whilst it is estimated that a maximum of 134 vessels could occur within the area of the Proposed Development at any one time (Table 4.1). However, this is within the context of high baseline levels of vessel traffic within this area (e.g. surveys recorded an average of 14 vessels per day within a 10 nm buffer around the Proposed Development over a 14-day period in August 2022, whilst also showing an average of three to four vessels intersecting the Proposed Development array area per day over summer - Offshore EIA Report, volume 2, chapter 13).
  3. When using the marine environment (and not at the breeding colony), guillemots are considered to have a moderate sensitivity to such sources of direct disturbance. Thus, reviews of the sensitivity of different seabird species to disturbance from vessels and helicopter traffic assign guillemot as ‘3’ on a five-scale ranking system, where 1 indicates hardly any or limited escape/avoidance behaviour and very short flight distance when approached and 5 indicates strong escape/avoidance behaviour and a large response distance (Garthe and Hüppop 2004, Furness et al. 2013).
  4. The total area to be affected by such disturbance over the full eight years of the construction phase also represents a small proportion of the total area of marine habitat available to guillemots from the Fowlsheugh SPA. Thus, the Proposed Development array area encompasses 1,010 km2, whilst the Proposed Development export cable corridor encompasses 168 km2. Together these areas represent approximately 3% of the total breeding season foraging area that is potentially available to the SPA guillemot population, as defined by the generic measure of the species’ mean maximum breeding season foraging range plus 1 SD (i.e. 73.2±80.5 km - Woodward et al. 2019) and assuming that this range is represented by a semicircle to the seaward side of the colony. Similarly, the Proposed Development array and export cable corridor represent approximately 14% of the breeding season foraging area if considering the mean maximum foraging range only. Additionally, modelling of guillemot foraging distributions, as derived from tracking data from the chick-rearing period, indicates that the Proposed Development array area and Proposed Development export cable corridor have minimal overlap with waters that are predicted to be used by birds from the Fowlsheugh SPA and exclude those areas of predicted greatest usage (Cleasby et al. 2018).
  5. During the non-breeding period, guillemot distribution is less constrained by the location of the breeding colonies but (as detailed above), for the purposes of the current assessment, it is assumed that the area occupied by the SPA population is defined by the mean maximum breeding season foraging range plus 1SD. Thus, the potential for effects of construction-related disturbance is assumed to be similar to that during the breeding season.
  6. In addition to the above, it is important to consider that the construction activities will not occur simultaneously across the entirety of the Proposed Development array area or the Proposed Development export cable corridor but, rather, will be carried out in different areas at different times. Thus, the activities will be concentrated within discrete (often small) parts of these wider areas, and within such areas they will not extend over the full duration of the construction phase, so further reducing the potential to which birds may be subject to disturbance effects. For example, cable laying for the Proposed Development export cable will occur over a total of two years, whilst within the Proposed Development array area it is likely that construction activities would be confined largely to discrete areas at any one time.
  7. The potential for disturbance effects during decommissioning is assumed to be the same (or less) as for construction, noting that the duration of the decommissioning phase will not exceed that of construction, and may be shorter.
  8. Given the moderate sensitivity of guillemot to disturbance effects, the relatively small areas that will be subject to activities with the potential to result in disturbance at any given time during the construction period and the fact that these potential effects will be temporary, it is considered that there is no potential for construction or decommissioning related disturbance to lead to an adverse effect on the Fowlsheugh SPA guillemot population.
Displacement
  1. As detailed above, guillemot is considered to have a moderate sensitivity to disturbance, whilst potential effects of disturbance during the construction and decommissioning phases will (at most) only extend across a small part of the wider foraging areas used by the Fowlsheugh SPA guillemot population and be limited to (at most) an eight year period during construction (and a likely similar or shorter period during decommissioning). Furthermore, as detailed above, potential effects of disturbance will not occur simultaneously across the entirety of the Proposed Development array area or Proposed Development export cable corridor but, rather, will be carried out in different areas at different times. Thus, at any given time the potential for disturbance effects that could lead to displacement of guillemots from this SPA will be limited to relatively small areas, with the potential effects also being of a temporary nature.
  2. Based upon the above, it is considered that there is relatively little potential for the Fowlsheugh SPA guillemot population to be affected by displacement during the construction or decommissioning phases, with any such effects only extending across relatively small areas and tending to be temporary in nature. Consequently, it is considered that there is no potential for construction or decommissioning related displacement to lead to an adverse effect on the Fowlsheugh SPA guillemot population.
Changes to prey availability
  1. Sandeels are key prey for guillemots, with a range of other species taken including clupeids (sprat and juvenile herring; del Hoyo et al., 1996). Indirect effects on guillemots may arise as a result of changes in the availability, distribution, or abundance of these species during the construction and decommissioning phases of the Proposed Development. Reduction or disruption to prey availability may cause displacement from foraging grounds or reduced energy intake, affecting survival rates or productivity in the Fowlsheugh SPA guillemot population in the short-term.
  2. During construction and decommissioning there are a number of ways in which effects on key prey species of seabirds may occur, which are outlined in the section on Project Alone: Construction and Decommissioning – Changes to Prey Availability for the St Abb’s Head to Fast Castle SPA kittiwake population. The evidence base and context for assessing the potential for such effects to have impacts on the Fowlsheugh SPA guillemot population are as for the St Abb’s Head to Fast Castle SPA guillemot population (and are detailed above in the equivalent section for that SPA population).
  3. Given this, it is considered that there is relatively little potential for the Fowlsheugh SPA guillemot population to be affected by changes to prey availability during the construction and decommissioning phases, with any such effects being largely intermittent across a relatively small spatial extent, with most effects temporary in nature. Consequently, it is considered that there is no potential for construction or decommissioning related changes in prey availability to lead to an adverse effect on the Fowlsheugh SPA guillemot population.
Project alone: operation and maintenance
Disturbance
  1. Vessel use and associated activities within the Proposed Development array area and export cable corridor during the operation and maintenance phase may lead to direct disturbance of guillemots from Fowlsheugh SPA. As described in the section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population, guillemots are considered to have a moderate sensitivity to such sources of direct disturbance at sea (Garthe and Hüppop 2004, Furness et al., 2013).
  2. The maximum design scenario is for up to 3,393 vessel round trips per year over the operational lifetime of the project. Vessel types which will be required during the operation and maintenance phase include those used during routine inspections, repairs and replacement of equipment, major component replacement, painting or other coatings, removal of marine growth, replacement of access ladders, and geophysical surveys (Table 4.1).
  3. Based on information presented in the section on Project Alone: Operation and Maintenance – Disturbance for the St Abb’s Head to Fast Castle SPA kittiwake population and in the Offshore EIA Report, volume 2, chapter 13, baseline levels of vessel traffic in the Offshore Ornithology study area are relatively high. In the context of the baseline levels of vessel traffic across the Offshore Ornithology study area, the increase during the operation and maintenance phase is considered to be relatively small. Vessel movements will be within the Proposed Development array area and export cable corridor and will follow existing shipping routes to/from ports. In addition, Project Codes of Conduct included as a part of the NSVMP (volume 4, appendix 25 of the Offshore EIA Report) will be issued to all project vessel operators to avoid sudden changes in course or speed which will minimise the potential for disturbance. Within the Proposed Development array area, movements and associated maintenance activities will be restricted to individual wind turbines over a period of days to weeks.
  4. The size and noise outputs from vessels during the operation and maintenance phase will be similar to those used in the construction phase. However, the number of vessel return trips per year and their frequency will be much lower for the operation and maintenance phase compared to the construction phase. In addition, activities during the operation and maintenance phase will not occur simultaneously across the entirety of the Proposed Development array area and export cable corridor but intermittently within discrete (often very small) parts of these wider areas.
  5. Given the discrete areas relative to the species’ foraging range that will be subject intermittently to potential disturbance from vessel use and maintenance activities (Woodward et al., 2019), and the fact that these potential effects will be reduced compared to the construction and decommissioning phases, it is considered that there is no potential for disturbance during operation and maintenance to lead to an adverse effect on the Fowlsheugh SPA guillemot population.