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 Forth Islands 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, Bogdanova et al. 2022), it is highly likely that during the breeding period guillemots from the Forth Islands 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 11% 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 guillemots 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 Forth Islands SPA guillemot population during the non-breeding period as during the breeding season, with 16% 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 - volume 2, chapter 13 of the Offshore EIA Report).
  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 Forth Islands 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 main 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.
  5. Tracking data (and associated modelling of foraging distributions) for guillemot suggest that the Proposed Development array area and Proposed Development export cable corridor have little overlap with waters that are heavily used by birds from the Forth Islands SPA during the breeding season (Cleasby et al. 2018, Bogdanova et al. 2022). For example, based on the data from 23 birds tracked from this SPA population during the 2021 breeding season, there is no overlap between the wider foraging and ‘resting at sea’ areas used by these birds (as defined by the respective 90% utilisation distributions) and either the Proposed Development array area or the Proposed Development export cable corridor, whilst none of the 278 individual flight tracks that were recorded from these birds passed through the Proposed Development array area (Bogdanova et al. 2022). Evidence from other tracking data collected during earlier studies also indicates minimal overlap between the areas of sea that are used by this SPA population and the Proposed Development (Cleasby et al. 2018).
  6. 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.
  7. 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.
  8. 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.
  9. 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 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 (Offshore EIA Report, volume 4, appendix 25) 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 Forth Islands SPA guillemot population.
Displacement/barrier effects
  1. As outlined above, displacement effects on the Forth Islands 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 Forth Islands 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 5.65). 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 Forth Islands 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 5.65:
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 Forth Islands SPA Population in Each Period. The Proportion of Adults Assumed to be Sabbaticals During the breeding Season is also Presented

Table 5.65: 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 Forth Islands 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 91 adult and 91 immature birds based on the lower mortality rates for the Scoping Approach (i.e. Scoping Approach A) and as 181 adult and 178 immature birds based upon the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B) (Table 5.66). The breeding season effects make the greatest contribution to these potential mortalities (comprising 77% and 65% of the total annual mortality for the lower and upper ranges, respectively) due to the larger mean peak population size and higher assumed mortality rates during this period (although the proportion of birds assumed to derive from the SPA population is greater during the non-breeding period) (Table 5.66).
  2. The annual mortality from displacement as determined using the Developer Approach is predicted to be 37 adult and 36 immature birds, equating to approximately 52% and 31% of the mortality predicted for the lower and upper range of the Scoping Approach, respectively (Table 5.66). In contrast to the Scoping Approach, the levels of predicted mortality are broadly similar for the breeding and non-breeding periods, with the difference between the Developer and Scoping Approaches in this respect being due to the fact that the Developer Approach assumes the same mortality rates in each seasonal period.

 

Table 5.66:
Estimated Potential Annual Mortality of Forth Islands 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 5.66: Estimated Potential Annual Mortality of Forth Islands 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 Forth Islands SPA population predicted due to displacement from the Proposed Development array represents 0.11% of the current adult breeding population at this colony (i.e. 34,580 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and between approximately 0.26 – 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 volume 3, appendix 11.6 of the Offshore EIA Report,), the estimates of adult mortality equate to an increase of 1.5% for the Developer Approach and of 3.6 – 7.2% for the lower and upper estimates from the Scoping Approach.
  2. The potential levels of impact on the Forth Islands 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 Forth Islands 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 Forth Islands SPA population.
  2. The same evidence basis and context in relation to this effect pathway for the operation and maintenance phase applies to the Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Tables 5.66 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 – 2021 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 5.67:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Forth Islands SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development Alone

Table 5.67: Projected 35 Year Population Sizes and Associated PVA Metrics for the Forth Islands SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development Alone

 

  1. The PVA predicted that the Forth Islands 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 almost three times larger than the current estimate of 34,580 adult birds under baseline conditions (i.e. no wind farm effects) and approximately twice its current size under the scenario of greatest annual mortality (i.e. Scoping Approach B) (Table 5.67). 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 trend does not reflect the documented long-term for this SPA population (Figure 5.21)
  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 5.67). 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 43.3 indicates a considerable overlap in the distributions of the predicted impacted and un-impacted population sizes and, hence, a reasonably 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 5.67). 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 Forth Islands 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 Forth Islands 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 Forth Islands SPA, as outlined above (Cleasby et al. 2018, Bogdanova et al. 2022).
Project alone: conclusion
  1. Based on the Developer Approach, the potential effects from the Proposed Development alone on the Forth Islands 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 reasonably 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. Although the SPA population has shown an overall decline in size since the early 2000’s there are suggestions from the recent count data of a reversal in this trend, and the population 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Offshore EIA Report, volume 3, appendix 11.6, estimates of displacement mortality during both the breeding and non-breeding periods which had been attributed to the Forth Islands 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 5.68).

 

Table 5.68:
Estimated Annual Mortality of Forth Islands 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 5.68: Estimated Annual Mortality of Forth Islands 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 approximate doubling in the predicted displacement mortality of adult birds compared to the Proposed Development alone for each of the Developer and Scoping Approaches (Tables 5.66 and 5.68). As for the Proposed Development alone, the breeding season effects make the greatest contribution to the potential mortality as determined by the Scoping Approach (comprising 77% and 65% of the total annual mortality for the lower and upper ranges, respectively), whilst for the Developer Approach the levels of predicted mortality are similar for each seasonal period.
  2. For the Proposed Development in-combination with the other UK North Sea wind farms, the additional annual mortality of adult guillemots from the Forth Islands SPA population predicted due to displacement represents between 0.24% of the current adult breeding population at this colony (i.e. 34,580 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and between 0.58 – 1.15% 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 3.3% for the Developer Approach and of 8.0 – 15.8% for the lower and upper estimates from the Scoping Approach.
  3. The potential levels of impact on the Forth Islands 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 5.68). 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 5.69:
Projected 35 Year Population Sizes and Associated PVA Metrics for the Forth Islands SPA Guillemot Population Under Different Impact Scenarios for the Proposed Development in-Combination with the Other UK North Sea Wind Farms

Table 5.69: Projected 35 Year Population Sizes and Associated PVA Metrics for the Forth Islands 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 5.67 with Table 5.69).
  2. For the Developer Approach, the CPS value indicates that the SPA population size would be reduced by approximately 9% after 35 years, relative to that in the absence of any wind farm effects (Table 5.69). The reduction in annual population growth rate (relative to that predicted under baseline conditions) remains small, whilst the centile value of 35.6 indicates moderate 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. 22 – 38%) 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 5.69).
  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 Forth Islands 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 Forth Islands 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 predicted levels of impact encompassed by the Scoping Approach would have the potential to result in an adverse effect on the Forth Islands 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 Forth Islands SPA razorbill population occurs on several islands in the Firth of Forth. The largest colony occurs on the Isle of May, with smaller colonies on Craigleith, Bass Rock, Fidra and The Lamb. The Isle of May colony represents approximately 90% of the total SPA population. The razorbill population size in the SPA has increased since 1985, and despite a period of decline in the mid 2000’s there has been sustained increases since 2013, with the population size being considerably higher than the citation level (Figure 5.22).

Figure 522:
Razorbill Population Trend at the Forth Islands SPA Between 1986 and 2019 (Noting that the Latest SPA Count is Shown for 2019 because it Spans the Period 2017 – 2021). The Red Line Shows the Citation Population Size for the SPA (2,800 Individuals)13. Data are from the Seabird Monitoring Programme Database (Seabird Monitoring Programme | JNCC (bto.org))

Figure 522: Razorbill Population Trend at the Forth Islands SPA Between 1986 and 2019 (Noting that the Latest SPA Count is Shown for 2019 because it Spans the Period 2017 – 2021). The Red Line Shows the Citation Population Size for the SPA (2,800 Individuals)13. 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 Forth Islands 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, Bogdanova et al. 2022), it is highly likely that during the breeding period razorbill from the Forth Islands 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 27% of the razorbill 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 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 Forth Islands 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, Offshore EIA Report, volume 3, appendix 11.5). Given this, the Proposed Development may have potential effects on the Forth Islands 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 Forth Islands 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 main seaward side of the colony. Similarly, the Proposed Development array and export cable corridor represent approximately 10% of the breeding season foraging area if considering the mean maximum foraging range only.
  5. Tracking data (and associated modelling of foraging distributions) for razorbill suggest that the Proposed Development array area and Proposed Development export cable corridor have little overlap with waters that are heavily used by birds from the Forth Islands SPA during the breeding season (Cleasby et al. 2018, Bogdanova et al. 2022). For example, based on the data from 11 birds tracked from this SPA population during the 2021 breeding season, the Proposed Development array area does not overlap with the core foraging or ‘resting at sea’ areas of the tracked birds (as defined by the respective 50% utilisation distribution), whilst overlaps with the wider foraging and ‘resting at sea’ areas (as defined by the respective 90% utilisation distributions of these tracked birds) represent 2% or less of these areas (Bogdanova et al. 2022). None of the 272 individual flight tracks that were recorded from these 11 tracked birds passed through the Proposed Development array area. Evidence from other tracking data collected during earlier studies also indicates minimal overlap between the areas of sea that are used by this SPA population and the Proposed Development (Cleasby et al. 2018).
  6. 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.
  7. 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.
  8. 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.
  9. 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 Forth Islands 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 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 (Offshore EIA Report, volume 4, appendix 25) 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 Forth Islands SPA razorbill population.
Displacement/barrier effects
  1. As outlined above, displacement effects on the Forth Islands 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 Forth Islands 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 (Offshore EIA Report, volume 3, appendix 11.5, Table 5.70). 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 Forth Islands SPA razorbill 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 5.70:
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 Forth Islands SPA Population in Each Period. The proportion of Adults Assumed to be Sabbaticals During the Breeding Season is also Presented

Table 5.70: 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 Forth Islands 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 11 adult and 10 immature birds based on the lower mortality rates for the Scoping Approach (i.e. Scoping Approach A) and as 19 adult and 17 immature birds based upon the higher mortality rates for the Scoping Approach (i.e. Scoping Approach B) (Table 5.71). The breeding season effects make the greatest contribution to these potential mortalities (comprising 92% and 87% 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 5.71).
  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 5.71). As for the Scoping Approach, effects during the breeding season make the greatest contribution (82%) 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 5.71:
Estimated Potential Annual Mortality of Forth Islands 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 5.71: Estimated Potential Annual Mortality of Forth Islands 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 Forth Islands SPA population predicted due to displacement from the Proposed Development array represents 0.04% of the current adult breeding population at this colony (i.e. 7,878 individuals – Table 3.3 in volume 3, appendix 11.5 of the Offshore EIA Report) as determined by the Developer Approach, and between approximately 0.14 – 0.24% 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), the estimates of adult mortality equate to an increase of 0.5% for the Developer Approach and of 1.5 – 2.7% for the lower and upper estimates from the Scoping Approach.
  2. The potential levels of impact on the Forth Islands 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.