Displacement/barrier effects
  1. As outlined above, displacement effects on the Fowlsheugh SPA guillemot population are estimated using the SNCB matrix approach, as applied to the Proposed Development array and two kilometre buffer (SNCBs 2022, Offshore EIA Report, volume 3, appendix 11.4). Thus, throughout this section, mortality from displacement is assumed to refer to that which results from both displacement and barrier effects. The approach used to derive predicted levels of mortality is as described in the section on Project Alone: Operation and Maintenance – Displacement/Barrier Effects for the St Abb’s Head to Fast Castle SPA kittiwake population above (and in the Offshore EIA Report, volume 3, appendix 11.4).
  2. On the basis of the advice provided in the Scoping Opinion (volume 3, appendix 6.2 of the Offshore EIA Report), displacement effects on guillemot are estimated for the breeding and non-breeding periods. The displacement and associated mortality rates advised in the Scoping Opinion (subsequently termed the Scoping Approach) for guillemot are:
  • Breeding period: 60% displacement with lower and upper mortality rates of 3% and 5%.
  • Non-breeding period: 60% displacement with lower and upper mortality rates of 1% and 3%.
    1. As with other species for which displacement effects are assessed (see above), the approach to estimating guillemot displacement effects advocated by the Scoping Opinion was considered overly precautionary in relation to both the displacement and mortality rates that were proposed, with these rates being higher than is considered to be justified on the basis of the available evidence (even when allowing for the incorporation of precaution in the assessment - volume 3, appendix 11.4, annex G of the Offshore EIA Report). Furthermore, the mortality rates advocated by the Scoping Opinion represented a marked change from the assumptions applied in assessments for other recent Scottish offshore wind farms (Marine Scotland 2017a,b,c) with no clear evidence apparently being available to justify such a change.
    2. Based upon a consideration of the available evidence for guillemot displacement, the potential consequent mortality, previous precedent and a need to incorporate precaution within the assessment, an alternative Developer Approach to estimating displacement effects was determined (volume 3, appendix 11.4, annex G of the Offshore EIA Report). The rates adopted by the Developer Approach are:
  • Breeding period: 50% displacement with a mortality rate of 1%.
  • Non-breeding period: 50% displacement with a mortality rate of 1%.
    1. Estimates of guillemot mortality were produced using the SNCB matrix on the basis of both the Scoping Approach and the Developer Approach (Offshore EIA Report, volume 3, appendix 11.4), with these estimates then apportioned to the Fowlsheugh SPA guillemot population during the breeding and non-breeding periods according to the MS Apportioning Tool (Butler et al. 2020) and the NatureScot (2018) approach, respectively (Offshore EIA Report, volume 3, appendix 11.5, Table 5.95). The resulting mortality estimates for the breeding and non-breeding periods were apportioned to age classes on the basis of the asymptotic age distribution of the population model used for the Fowlsheugh SPA guillemot PVAs in this assessment (Offshore EIA Report, volume 3, appendix 11.6). Based on advice provided by NatureScot and Marine Scotland Science following Roadmap Meeting 4 (G. Holland, email 26/01/2022), it was also assumed that 7% of the breeding adults in the SPA population miss breeding in any given year (i.e. sabbatical birds) so that the number of estimated adult deaths during the breeding season was adjusted accordingly.
Table 5.95:
The Mean Peak Abundance Estimates of Guillemot in the Proposed Development Array Area and 2 km Buffer for Each Seasonal Period, together with the Proportion of Birds Estimated to Belong to the Breeding Adult Age Class and to be from the Fowlsheugh SPA Population in Each Period. The proportion of Adults Assumed to be Sabbaticals During the Breeding Season is also Presented

Table 5.95: The Mean Peak Abundance Estimates of Guillemot in the Proposed Development Array Area and 2 km Buffer for Each Seasonal Period, together with the Proportion of Birds Estimated to Belong to the Breeding Adult Age Class and to be from the Fowlsheugh SPA Population in Each Period. The proportion of Adults Assumed to be Sabbaticals During the Breeding Season is also Presented

 

  1. Based upon the estimates and assumptions detailed above, the potential annual mortality amongst the SPA guillemot population as a result of displacement is estimated as 260 adult and 261 immature birds based on the lower mortality rates for the Scoping Approach (i.e. Scoping Approach A) and as 473 adult and 473 immature birds based upon the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B) (Table 5.96). The breeding season effects make the greatest contribution to these potential mortalities (comprising 89% and 81% of the total annual mortality for the lower and upper ranges, respectively) due to the larger mean peak population size, higher assumed mortality rates and higher proportion of birds assumed to derive from the SPA population during the breeding period (Table 5.96).
  2. The annual mortality from displacement as determined using the Developer Approach is predicted to be 89 adult and 88 immature birds, equating to approximately 34% and 19% of the mortality predicted for the lower and upper range of the Scoping Approach, respectively (Table 5.96). The breeding season effects comprise 72% of the total annual mortality, as determined by the Developer Approach.

 

Table 5.96:
Estimated Potential Annual Mortality of Fowlsheugh SPA Guillemots as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach

Table 5.96: Estimated Potential Annual Mortality of Fowlsheugh SPA Guillemots as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach

 

  1. The additional annual mortality of adult guillemot from the Fowlsheugh SPA population predicted due to displacement from the Proposed Development array represents 0.10% of the current adult breeding population at this colony (i.e. 91,358 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and between approximately 0.28 - 0.52% of this population as determined by the lower and upper estimates from 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 0.073 – see Table 2.9 in the Offshore EIA Report, volume 3, appendix 11.6), the estimates of adult mortality equate to an increase of 1.3% for the Developer Approach and of 3.9 – 7.1% for the lower and upper estimates from the Scoping Approach.
  2. The potential levels of impact on the Fowlsheugh SPA guillemot population resulting from the mortality predicted from displacement and barrier effects associated with the Proposed Development array during the operation and maintenance phase 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 displacement mortality on the SPA population.
Changes to prey availability
  1. Potential impacts on key prey species for guillemots 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, reductions in water clarity, EMF from subsea electrical cabling, and colonisation of subsea structures, could affect guillemot survival and productivity in the Fowlsheugh SPA population.
  2. The same evidence basis and context in relation to this effect pathway for the operation and maintenance phase applies to the Fowlsheugh SPA guillemot population as to the St Abb’s Head to Fast Castle SPA guillemot population. This is detailed in the section on Project Alone: Operation and Maintenance – Changes to Prey Availability for the St Abb’s Head to Fast Castle 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 operation and maintenance phase, with any such effects being largely intermittent across a relatively small spatial extent. Consequently, 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 guillemot population.
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 guillemot population are limited to displacement (inclusive of barrier effects) 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 displacement effects associated with the Proposed Development, as determined by both the Scoping and Developer Approaches (see Table 5.96 above). The population model for the SPA population was a stochastic, density independent, matrix model, based upon the demographic parameters specified in Table 2.9 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 (Offshore EIA Report 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 to Fast Castle SPA kittiwake population 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 5.97:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development Alone

Table 5.97: Projected 35 Year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development Alone

 

  1. The PVA predicted that the Fowlsheugh SPA guillemot population would increase over the 35 year projection period irrespective of the effects from the Proposed Development. Thus, the population is predicted to be three times larger than the current estimate of 91,358 adult birds under baseline conditions (i.e. no wind farm effects) and more than twice its current size under the scenario of greatest annual mortality (i.e. Scoping Approach B) (Table 5.97). Given that 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 predicted increases are inevitably greatest for the baseline scenario and least for the scenario involving highest annual mortality (i.e. Scoping Approach B). 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 differs from the documented long-term trend of relative stability for this SPA population (as indexed by the trend for the Fowlsheugh RSPB reserve - Figure 5.25).
  2. The PVA metrics suggest relatively marked differences in the predicted population-level impacts according to the Developer and Scoping Approaches. Thus, for the Developer Approach, the CPS value indicates that the displacement effects from the Proposed Development alone would result in a reduction of 4% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects (Table 5.97). The associated reduction in annual population growth rate (relative to that predicted under baseline conditions) is estimated to be 0.1%, whilst the centile value of 44.3 indicates a 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.
  3. For the Scoping Approach, the CPS values indicate a reduction of 11 – 20% in population size after 35 years, relative to that in the absence of any wind farm effects (Table 5.97). The reduction in annual population growth rate (relative to that predicted under baseline conditions) is estimated to be 0.3 – 0.6%. The centile metric indicates low to moderate overlap in the distribution of the predicted impacted and un-impacted population sizes, suggesting a reasonably high likelihood of the impacted population being smaller than the un-impacted population after 35 years.
  4. For the same reasons as described in the section on Project-Alone: Population-Level Impacts for the St Abb’s Head to Fast Castle SPA guillemot population, the assessment of the Fowlsheugh SPA guillemot population incorporates high levels of precaution, which extend beyond the differences between the Developer and Scoping Approaches that are outlined above (and detailed in the Offshore EIA Report, volume 3, appendix 11.4). Notably, the concerns over the extent to which the seasonal mean peak abundances (which provide the basis for the displacement mortality estimates) are likely to be representative of the overall usage of the Proposed Development array and two kilometre buffer by guillemot are equally relevant to the Fowlsheugh SPA population as to the St Abb’s Head to Fast Castle SPA population. As for the St Abb’s Head to Fast Castle SPA population, the evidence available from tracking data suggests low levels of usage of the Proposed Development array area and two kilometre buffer during the breeding season by guillemots from the Fowlsheugh SPA, as outlined above (Cleasby et al. 2018).
Project alone: conclusion
  1. Based on the Developer Approach, the potential effects from the Proposed Development alone on the Fowlsheugh SPA guillemot population are predicted to be relatively 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. The size of the SPA population has been relatively stable over the long-term, remains above the citation level and is considered to be in ‘favourable maintained’ condition. Given this, it is concluded that the effects from the Proposed Development alone would not result in an adverse effect on this population.
  2. The Scoping Approach predicts greater effects from the Proposed Development alone, with the potential resultant population-level impacts being relatively large when considering the upper range of the effects. These potential impacts are of a scale which would be considered likely to result in an adverse effect on the SPA population. However, as has been detailed above (and in Offshore EIA Report, volume 3, appendix 11.4), it is considered that the level of effects on guillemots assumed by the Scoping Approach are overly precautionary and without any reasonable basis or support from the available evidence. The potential for gross overestimation of the population-level impacts is further exacerbated by other precautionary elements of the assessment, which have been incorporated irrespective of the Developer or Scoping Approaches. Given this, it is considered that greater weight should be given to the conclusions as determined by the Developer Approach, which concluded no adverse effect on the Fowlsheugh SPA guillemot population as a result of the Proposed Development alone.
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 guillemot population during construction and decommissioning and resulting from disturbance and 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 guillemot population in-combination with other plans and projects is limited to the displacement (inclusive of barrier effects) 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)).
Displacement/barrier effects – operation and maintenance
  1. As described in annex E of the Offshore EIA Report, volume 3, appendix 11.4, estimates of displacement mortality during both the breeding and non-breeding periods which had been attributed to the Fowlsheugh SPA guillemot population were extracted from the existing assessments for offshore wind farms that are in planning, consented, under construction or in operation. As for the potential displacement mortality estimated for the Proposed Development, the mortality attributed to the SPA population from other offshore wind farms was estimated using the SNCB matrix approach, with details on the displacement and mortality rates that had been applied being available in each case. Thus, it was possible to adjust the estimated mortalities from each of the other projects to align with the displacement and mortality rates on which the Scoping and Developer Approaches are based.
  2. The potential mortality estimates derived for the other 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. However, the potential effects on the SPA population were limited to the other Forth and Tay wind farms, noting that apportioning of the non-breeding season effects for guillemot did not rely on the BDMPS approach (as stated above, see also volume 3, appendix 11.5 of the Offshore EIA Report). Given that these two different in-combination scenarios are equivalent, the predicted effects are reported solely for the UK North Sea wind farms in the tables below (Table 5.98).

 

Table 5.98:
Estimated Annual Mortality of Fowlsheugh SPA Guillemots as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach, In-Combination with the other UK North Sea Wind Farms

Table 5.98: Estimated Annual Mortality of Fowlsheugh SPA Guillemots as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach, In-Combination with the other UK North Sea Wind Farms

1The Forth and Tay and UK North Sea in-combination effects for the SPA population are equivalent (so that they are reported for the latter scenario only).

 

  1. Incorporating the potential mortality predicted from the displacement effects associated with the other UK North Sea wind farms leads to an increase of approximately 65 – 70% in the predicted displacement mortality of adult birds compared to the Proposed Development alone for each of the Developer and Scoping Approaches (Tables 5.96 and 5.98). As for the Proposed Development alone, the breeding season effects make the greatest contribution to the potential mortality as determined by the Scoping and Developer Approaches (comprising 66 - 85% of the total annual mortality), with this seasonal difference in the scale of the effects again greatest for the Scoping Approach.
  2. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult guillemots from the Fowlsheugh SPA population predicted due to displacement represents between 0.17% of the current adult breeding population at this colony (i.e. 91,358 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and between 0.47 – 0.88% as determined by the lower and upper estimates from the Scoping Approach. In terms of percentage increases in the baseline annual adult mortality of the population (based on applying a mortality rate of 0.073 – see Table 2.9 in volume 3, appendix 11.6 of the Offshore EIA Report), the estimates of adult displacement mortality equate to an increase of 2.3% for the Developer Approach and of 6.5 – 12.0% for the lower and upper estimates from the Scoping Approach.
  3. The potential levels of impact on the Fowlsheugh SPA guillemot population resulting from the predicted mortality from displacement and barrier effects associated with the Proposed Development 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 potential effects of predicted displacement mortality on the SPA population.
In-combination: population-level impacts
  1. PVA was undertaken on the mortality to the adult and immature age classes predicted due to the displacement effects associated with the Proposed Development in-combination with the other UK North Sea wind farms, as determined by both the Scoping and Developer Approaches (Table 5.98). 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 5.99:
Projected 35 year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development In-Combination with the other UK North Sea Wind Farms

Table 5.99: Projected 35 year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Guillemot 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 the other UK North Sea wind farms suggest greater population-level impacts than as predicted for the Proposed Development alone (compare Table 5.99 with Table 5.97).
  2. For the Developer Approach, the CPS value indicates that the SPA population size would be reduced by approximately 7% after 35 years, relative to that in the absence of any wind farm effects (Table 5.99). The reduction in annual population growth rate (relative to that predicted under baseline conditions) remains small, whilst the centile value of 39.8 indicates considerable overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a reasonable likelihood of the impacted population being of a similar size to the un-impacted population after 35 years.
  3. The metrics associated with the Scoping Approach indicate markedly greater levels of impact, with sizeable reductions (i.e. 18 – 31%) in the predicted population size after 35 years relative to that predicted to occur in the absence of wind farm effects, and with the values of the centile metric indicating a high likelihood of the impacted population size being smaller than the un-impacted population size after 35 years (Table 5.99).
  4. As explained above, the assessment for the Proposed Development in-combination with the other Forth and Tay wind farms is equivalent to that for the Proposed Development in-combination with the other UK North Sea wind farms in the case of this SPA population.
In-combination: conclusion
  1. On the basis of the Developer Approach, the potential effects from the Proposed Development in-combination with the other UK North Sea wind farms on the Fowlsheugh SPA guillemot population are predicted to be relatively small, with the resultant population-level impacts also predicted to be small. In addition, the PVA metrics indicate a reasonable likelihood of the population being of a similar size to that which would occur in the absence of the Proposed Development after 35 years. Considering this within the context of the ‘favourable maintained’ condition of the SPA population, it is concluded that the potential effects from the Proposed Development in-combination with the other UK North Sea wind farms would not result in an adverse effect on the Fowlsheugh SPA guillemot population.
  2. For the Scoping Approach, the potential effects resulting from the Proposed Development in-combination with the other UK North Sea wind farms are markedly greater than as predicted by the Developer Approach. It is considered that the potential levels of impact encompassed by the Scoping Approach would have the potential to result in an adverse effect on the Fowlsheugh SPA guillemot population. As for the Proposed Development alone, this conclusion should be considered within the context of the high levels of precaution incorporated in the assessment, particularly as determined by the Scoping Approach. As such, it is considered that greater weight should be given to the conclusions as determined by the Developer Approach.

Assessment for the razorbill population

  1. The Fowlsheugh SPA razorbill population is currently estimated to number 17,817 breeding individuals, which is substantially above the citation population size of 5,800 individuals (volume 3, appendix 11.5 of the Offshore EIA Report). As for the Fowlsheugh SPA kittiwakes, earlier estimates of the size of the SPA razorbill 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, whilst there are few years with counts undertaken across the entire SPA. However, it is apparent from the available data that the Fowlsheugh RSPB reserve holds the vast majority of the SPA population, with an estimated 88% of the current population estimated to be within this site (based upon the 2018 count data). The SPA population estimate used for the current assessment derives from 2018 and is corrected to align with the SPA boundaries.
  2. Based on the counts from the Fowlsheugh RSPB reserve, the SPA razorbill population size appears to have been relatively stable since the mid 1980s but with a marked increase in recent years. The counts from the Fowlsheugh RSPB reserve are above, or close to, the citation level in all years for which data are available (Figure 5.26).

Figure 526:
Razorbill Population Trend at the Fowlsheugh RSPB Reserve Between 1986 and 2018 (Noting that this Site Accounts for a High Proportion of the SPA Population – see text). The Red Line Shows the Citation Population Size for the SPA (5,800 INDIVIDUALS13). Data are from the Seabird Monitoring Programme Database (Seabird Monitoring Programme | JNCC (bto.org))

Figure 526: Razorbill Population Trend at the Fowlsheugh RSPB Reserve Between 1986 and 2018 (Noting that this Site Accounts for a High Proportion of the SPA Population – see text). The Red Line Shows the Citation Population Size for the SPA (5,800 INDIVIDUALS13). Data are from the Seabird Monitoring Programme Database (Seabird Monitoring Programme | JNCC (bto.org))

 

The potential for impacts on the razorbill 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 razorbill 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 razorbill 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 razorbill 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 29% of the razorbill occurring on the Proposed Development array area during the breeding season derive from this SPA colony (volume 3, appendix 11.5 of the Offshore EIA Report). The breeding period for razorbill 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), which draws upon the findings from Buckingham et al. (2022), razorbills are assumed to disperse more widely than guillemots during the non-breeding period, with their distribution concentrated in central areas of the North Sea during the mid-winter period. Consequently, it is assumed (for the purposes of the assessment) that during the non-breeding period birds from the Fowlsheugh SPA population have the potential to occur within offshore wind farms throughout the UK North Sea waters during the autumn and spring passage periods and in mid-winter (defined as mid-August to October, January to March and November to December, respectively, on the basis of applying the BDMPS defined periods within the context of the overall non-breeding period defined by NatureScot – Furness 2015, NatureScot 2020, volume 3, appendix 11.5 of the Offshore EIA Report). Given this, the Proposed Development may have potential effects on the Fowlsheugh SPA razorbill population during breeding and non-breeding periods.
Project alone: construction and decommissioning
Disturbance
  1. Direct disturbance to razorbills 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), razorbills 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 razorbill 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 razorbills 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 razorbill population, as defined by the generic measure of the species’ mean maximum breeding season foraging range plus 1 SD (i.e. 88.7±75.9 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 area and export cable corridor represent approximately 10% of the breeding season foraging area if considering the mean maximum foraging range only. Modelling of razorbill foraging distributions, as derived from tracking data from the chick-rearing period, indicates that the Proposed Development has minimal overlap with waters that are predicted to be used by birds from the Fowlsheugh SPA and is beyond those areas of most concentrated usage (Cleasby et al. 2018).
  5. During the non-breeding periods, razorbill distribution is not constrained by the location of the breeding colonies and birds from the SPA population are likely to occur across large parts of the North Sea (Furness 2015, Buckingham et al. 2022) so that the potential for effects of construction-related disturbance is lower than 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 razorbill 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 razorbill population.
Displacement
  1. As detailed above, razorbill is considered to have a moderate sensitivity to disturbance, whilst potential effects of disturbance during the construction and decommissioning phases will only extend across a small part of the wider foraging areas used by the Fowlsheugh SPA razorbill 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 razorbills 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 razorbill 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 razorbill population.
Changes to prey availability
  1. Sandeels are key prey for razorbills, with a range of other species taken including sprat and juvenile herring (del Hoyo et al., 1996). Indirect effects on razorbills 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 razorbill 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 razorbill population are as for the St Abb’s Head to Fast Castle SPA razorbill 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 razorbill 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 razorbill 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 razorbills from Fowlsheugh SPA. As described in the section on Project Alone: Construction and Decommissioning – Disturbance for the SPA population, razorbills 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 volume 2, chapter 13 of the Offshore EIA Report, 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 offshore 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 razorbill population.
Displacement/barrier effects
  1. As outlined above, displacement effects on the Fowlsheugh SPA razorbill population are estimated using the SNCB matrix approach, as applied to the Proposed Development array and two kilometre buffer (SNCBs 2022, Offshore EIA Report, volume 3, appendix 11.4). Thus, throughout this section, mortality from displacement is assumed to refer to that which results from both displacement and barrier effects. The approach used to derive predicted levels of mortality is as described in the section on Project Alone: Operation and Maintenance – Displacement/Barrier Effects for the St Abb’s Head to Fast Castle SPA kittiwake population above (and in the Offshore EIA Report, volume 3, appendix 11.4).
  2. On the basis of the advice provided in the Scoping Opinion (volume 3, appendix 6.2 of the Offshore EIA Report), displacement effects on razorbill are estimated for the breeding and non-breeding periods. The displacement and associated mortality rates advised in the Scoping Opinion (subsequently termed the Scoping Approach) for razorbill are:
  • Breeding period: 60% displacement with lower and upper mortality rates of 3% and 5%.
  • Non-breeding period: 60% displacement with lower and upper mortality rates of 1% and 3%.
    1. As with other species for which displacement effects are assessed (see above), the approach to estimating razorbill displacement effects advocated by the Scoping Opinion was considered overly precautionary in relation to both the displacement and mortality rates that were proposed, with these rates being higher than is considered to be justified on the basis of the available evidence (even when allowing for the incorporation of precaution in the assessment - volume 3, appendix 11.4, annex G of the Offshore EIA Report). Furthermore, the mortality rates advocated by the Scoping Opinion represented a marked change from the assumptions applied in assessments for other recent Scottish offshore wind farms (Marine Scotland 2017a,b,c) with no clear evidence apparently being available to justify such a change.
    2. Based upon a consideration of the available evidence for razorbill displacement, the potential consequent mortality, previous precedent and a need to incorporate precaution within the assessment, an alternative Developer Approach to estimating displacement effects was determined (volume 3, appendix 11.4, annex G of the Offshore EIA Report). The rates adopted by the Developer Approach are:
  • Breeding period: 50% displacement with a mortality rate of 1%.
  • Non-breeding period: 50% displacement with a mortality rate of 1%.
    1. Estimates of razorbill mortality were produced using the SNCB matrix on the basis of both the Scoping Approach and the Developer Approach (Offshore EIA Report, volume 3, appendix 11.4), with these estimates then apportioned to the Fowlsheugh SPA razorbill population during the breeding and non-breeding periods according to the MS Apportioning Tool (Butler et al. 2020) and the BDMPS approach (Furness 2015), respectively (volume 3, Offshore EIA Report, volume 3, appendix 11.5; Table 5.100). The resulting mortality estimates for the breeding period were apportioned to age classes on the basis of the asymptotic age distribution of the population model used for the Fowlsheugh SPA razorbill PVAs in this assessment (volume 3, appendix 11.6 of the Offshore EIA Report). Based on advice provided by NatureScot and Marine Scotland Science following Roadmap Meeting 4 (G. Holland, email 26/01/2022), it was also assumed that 7% of the breeding adults in the SPA population miss breeding in any given year (i.e. sabbatical birds) so that the number of estimated adult deaths during the breeding season was adjusted accordingly.

 

Table 5.100:
The Mean Peak Abundance Estimates of Razorbill in the Proposed Development Array Area and 2 km Buffer for each Seasonal Period, Together with the Proportion of Birds Estimated to Belong to the Breeding Adult Age Class and to be from the Fowlsheugh SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals During the Breeding Season is also Presented

Table 5.100: The Mean Peak Abundance Estimates of Razorbill in the Proposed Development Array Area and 2 km Buffer for each Seasonal Period, Together with the Proportion of Birds Estimated to Belong to the Breeding Adult Age Class and to be from the Fowlsheugh SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals During the Breeding Season is also Presented

 

  1. Based upon the estimates and assumptions detailed above, the potential annual mortality amongst the SPA razorbill population as a result of displacement is estimated as 13 adult and 10 immature birds based on the lower mortality rates for the Scoping Approach (i.e. Scoping Approach A) and as 23 adult and 18 immature birds based upon the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B) (Table 5.101). The breeding season effects make the greatest contribution to these potential mortalities (comprising 93% and 84% of the total annual mortality for the lower and upper mortality rates, respectively) due to the higher assumed mortality rates and higher proportion of birds assumed to derive from the SPA population during this period (Table 5.101).
  2. The annual mortality from displacement as determined using the Developer Approach is predicted to be 4 adult and 3 immature birds, equating to approximately 33% and 18% of the mortality predicted for the lower and upper range of the Scoping Approach, respectively (Table 5.101). As for the Scoping Approach, effects during the breeding season make the greatest contribution (79%) to the predicted annual mortality, with this being slightly less marked because the mortality rates for each seasonal period are assumed to be same under the Developer Approach.

 

Table 5.101:
Estimated Potential Annual Mortality of Fowlsheugh SPA Razorbills as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach

Table 5.101: Estimated Potential Annual Mortality of Fowlsheugh SPA Razorbills as a Result of Displacement from the Proposed Development Array Area and 2 km Buffer as Determined by the Scoping Approach and Developer Approach

 

  1. The additional annual mortality of adult razorbill from the Fowlsheugh SPA population predicted due to displacement from the Proposed Development array represents 0.02% of the current adult breeding population at this colony (i.e. 17,817 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and between approximately 0.07 – 0.13% of this population as determined by the lower and upper estimates from 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 0.090 – see Table 2.19 in volume 3, appendix 11.6 of the Offshore EIA Report), the estimates of adult mortality equate to an increase of 0.3% for the Developer Approach and of 0.8 – 1.4% for the lower and upper estimates from the Scoping Approach.
  2. The potential levels of impact on the Fowlsheugh SPA razorbill population resulting from the mortality predicted from displacement and barrier effects associated with the Proposed Development array during the operation and maintenance phase 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 displacement mortality on the SPA population.
Changes to prey availability
  1. Potential impacts on key prey species for razorbills breeding at 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, reductions in water clarity, EMF from subsea electrical cabling, and colonisation of subsea structures, could affect razorbill survival and productivity in the Fowlsheugh SPA population.
  2. The same evidence basis and context in relation to this effect pathway for the operation and maintenance phase applies to the Fowlsheugh SPA razorbill population as to the St Abb’s Head to Fast Castle SPA razorbill population. This is detailed in the section on Project Alone: Operation and Maintenance – Changes to Prey Availability for the St Abb’s Head to Fast Castle SPA population.
  3. Given this, it is considered that there is relatively little potential for the Fowlsheugh SPA razorbill population to be affected by changes to prey availability during the operation and maintenance phase, with any such effects being largely intermittent across a relatively small spatial extent. Consequently, 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 razorbill population.
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 razorbill population are limited to displacement (inclusive of barrier effects) 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 displacement effects associated with the Proposed Development, as determined by both the Scoping and Developer Approaches (see Table 5.101 above). The population model for the SPA population was a stochastic, density independent, matrix model, based upon the demographic parameters specified in Table 2.19 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 (Offshore EIA Report, 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 to Fast Castle SPA kittiwake population 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 5.102:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Razorbill Population Under Different Impact Scenarios for the Proposed Development Alone.

Table 5.102: Projected 35 Year Population Sizes and Associated PVA Metrics for the Fowlsheugh SPA Razorbill Population Under Different Impact Scenarios for the Proposed Development Alone.

 

  1. The PVA predicted that the Fowlsheugh SPA razorbill population would increase over the 35 year projection period irrespective of the effects from the Proposed Development. Thus, the population is predicted to increase by 68% from the current estimate of 17,817 adult birds under baseline conditions (i.e. no wind farm effects) and by 59% under the scenario of greatest annual mortality (i.e. Scoping Approach B), respectively (Table 5.102). Given that 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 predicted increases are inevitably greatest for the baseline scenario and least for the scenario involving highest annual mortality (i.e. Scoping Approach B). The prediction of an increasing population trend has some, broad level, consistency with the documented long-term trend for this SPA population (as indexed by the trend for the Fowlsheugh RSPB reserve) of relative stability with a recent marked increase (Figure 5.26).
  2. The PVA metrics suggest relatively small effects overall. Thus, the CPS value for the Developer Approach indicates that the displacement effects from the Proposed Development alone would result in a reduction of 1% in the size of the SPA population after 35 years, relative to that in the absence of any wind farm effects, whilst for the Scoping Approach the CPS values indicate reductions of 3 – 5% after 35 years, relative to that in the absence of any wind farm effects (Table 5.102). The associated reduction in annual population growth rate (relative to that predicted under baseline conditions) is not detectable for the Developer Approach (at least when the CPGR value is expressed to three decimal places) and is only 0.1% for the Scoping Approach. The centile values are all above 45, 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 (Table 5.102).
  3. For the same reasons as described in the section on Project-Alone: Population-Level Impacts for the St Abb’s Head to Fast Castle SPA razorbill population, the assessment of the Fowlsheugh SPA razorbill population incorporates high levels of precaution, which extend beyond the differences between the Developer and Scoping Approaches that are outlined above (and detailed in the Offshore EIA Report, volume 3, appendix 11.4). Notably, the concerns over the extent to which the seasonal mean peak abundances (which provide the basis for the displacement mortality estimates) are likely to be representative of the overall usage of the Proposed Development array and two kilometre buffer by razorbill are equally relevant to the Fowlsheugh SPA population as to the St Abb’s Head to Fast Castle SPA population. As for the St Abb’s Head to Fast Castle SPA population, the evidence available from tracking data suggests low levels of usage of the Proposed Development array area and two kilometre buffer during the breeding season by razorbills from the Fowlsheugh SPA, as outlined above (Cleasby et al. 2018).
Project alone: conclusion
  1. It is considered that the predicted levels of impact from the Proposed Development alone on the Fowlsheugh SPA razorbill population are of a relatively small scale, as determined by both the Developer and Scoping Approaches. For both the Developer and Scoping Approaches it is also the case that the centile metric indicates a high likelihood of the impacted population being of similar size to the un-impacted population after 35 years. These levels of impact are within the context of an assessment which incorporates high levels of precaution (particularly as determined by the Scoping Approach) and a population for which the documented, long-term, trend is relative stability with a recent marked increase, and which is considered to be in ‘favourable maintained’ condition. Given this, it is concluded that the effects from the Proposed Development alone (as determined by either the Developer or Scoping Approaches) would not result in an adverse effect on this SPA 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 razorbill population during construction and decommissioning and resulting from disturbance and 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 razorbill population in-combination with other plans and projects is limited to the displacement (inclusive of barrier effects) 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)).