Publication - Publication

Offshore wind energy - draft sectoral marine plan: habitat regulations appraisal

Published: 18 Dec 2019
Directorate:
Marine Scotland Directorate
Part of:
Energy, Marine and fisheries
ISBN:
9781839603754

The habitats regulations appraisal is completed in accordance with the Habitats Regulations that implement the EC Habitats and Birds Directives in UK waters and has been completed for the sectoral marine plan for offshore wind.

Contents
Offshore wind energy - draft sectoral marine plan: habitat regulations appraisal
6 Potential for Adverse Effects on Bird Features

6 Potential for Adverse Effects on Bird Features

6.1 Introduction

6.1.1 Following the screening process, a total of 468 European/Ramsar sites was identified for which there is a LSE (or the potential for a LSE cannot be excluded).  Of these sites, a large number of European/Ramsar sites were identified at which it was not possible to conclude that there would be no LSE from the Draft Plan for some, or all, of the qualifying bird interest features. In total there were 135 SPAs, 15 pSPAs and a further 51 Ramsar Sites with qualifying bird or habitat interest features that were screened in.

6.1.2 Given the broad area covered by the Draft Plan and the large number of sites screened into these assessments, the method adopted aligns with that carried out in previous HRAs (e.g. [36] [37][38]). Essentially an individual review of the full list of screened in sites and the qualifying bird interest features that they support, has not been done. However, acknowledging recent consultation responses to project level HRAs for offshore wind development in Moray, Forth and Tay regions issued in 2018, consideration at a regional level has been given to the potential for cumulative effects on identified seabird species of concern (see Section 11).

6.1.3 The individual sites that were screened in for each of the 17 DPOs are shown in the screening tables (schedules) and maps (Tables D1-D17; Figures E1-E17). The locations of the SPA and Ramsar sites which were screened in are also provided in Figure 4 and Figure 5.

6.1.4 The SPA and Ramsar sites also contained other interest features for which it could not be concluded that there was no LSE (e.g. eelgrass) and/or the habitats within them are an important component of the functionality of the European/Ramsar sites (e.g. because they provide foraging ground for bird species) and therefore have assigned conservation objectives.  The effects on these other features are reviewed separately under the relevant assessment section(s) of this report that deal with these other habitat/species groups.

6.1.5 In summary, the screening phase concluded that there is a possibility of a LSE (or that it was not possible to conclude no LSE) to qualifying bird interest features.  To assess whether there is any adverse effect on the integrity of relevant European/Ramsar sites, the following sections review the sensitivities of the associated bird features, identify the conservation objectives and assess, in tabular format, the effects arising in the context of the proposed plan-level mitigation measures.

6.2 Sensitivities of Bird Interest Features to the Sectoral Offshore Wind Plan Activities

6.2.1 This section reviews the sensitivities that are relevant for the qualifying bird interest features.  A generic review of the sensitivities of relevant bird features is presented under the impact pathways identified during the screening phase (see Table 2):

  • Physical Loss/Gain of Habitat (Foraging and Onshore Habitat Loss);
  • Physical Loss/Gain of Habitat (Fish Aggregation or Artificial Reef);
  • Physical Damage to Habitat (Reduction in Habitat Quality);
  • Physical Damage to Species (Collision Risk);
  • Non-Physical Disturbance (Noise/Visual Disturbance Causing Exclusion Effects);
  • Toxic Contamination (Contamination and Spillages); and
  • Non-Toxic Contamination (Increased Turbidity).

6.2.2 Following this review, the general characteristics and sensitivities of relevant bird interest features are presented and reviewed against the Draft Plan activities that could cause a LSE.

6.2.3 It should be noted throughout this section that different species will have different sensitivities to effects according to several factors including:

  • Whether they forage by diving or at the surface;
  • Whether they forage nocturnally/crepuscularly or diurnally; and
  • Whether they are ground/burrow/crevice-nesting species or cliff-nesters.

6.2.4 A categorisation of species, taken from Garthe, S. & Hüppop, O.[39]  is summarised in Table 8. Recent discussion in Furness et al[40], has recognised that in some cases there may be a lack of evidence regarding nocturnal activities, therefore any future project level HRAs should consider individual species behaviour and current research.

Table 8: Breeding/foraging parameters of breeding seabirds which influence sensitivities

Breeding Receptors Foraging Mode Nocturnal Flight/Diving Activity Nesting Location
Red-throated Diver Pursuit-diver No Ground
N. Fulmar Surface feeder Yes Cliff
Manx Shearwater Surface/Pursuit-diver Yes Burrow/crevice
Storm Petrel Surface feeder Yes Burrow/crevice
Leach’s Petrel Surface feeder Yes Burrow/crevice
Gannet Plunge/Pursuit-diver No Ground/cliff
Cormorant Pursuit-diver No Cliff/above ground
Shag Pursuit-diver No Cliff
Common Scoter Diver/Pursuit-diver No Ground
Arctic Skua Surface feeder No Ground
Great Skua Surface feeder No Ground
Herring Gull Surface feeder Yes Ground
Great B-b Gull Surface feeder Yes Ground
B. L. Kittiwake Surface feeder Yes Cliff
Arctic Tern Surface feeder No Ground
Guillemot Pursuit-diver Crepuscular Cliff
Razorbill Pursuit-diver Crepuscular Cliff
A. Puffin Pursuit-diver Crepuscular Burrow/crevice

(Sources: Gaston and Jones[41]; Garthe and Hüppop[42])

6.3 Physical Loss/Gain of Habitat (Foraging and Onshore Habitat Loss; Impact Pathway 2)

6.3.1 Seabed habitat important for foraging seabirds and their prey may be lost as a result of the installation of cables and devices.  Similar temporary losses of habitat will also occur during decommissioning.  The risk and magnitude of such direct effects on the seabed habitats will be dependent on a range of factors such as the habitat type, the extent of habitat affected, the location and the nature of activities and whether they are temporary or permanent.

6.3.2 Although the direct loss of terrestrial habitats as a result of cable installation or any landside infrastructure works also poses a risk, the potential effects from terrestrial development are outside the scope of the plan level HRA.  Loss of breeding habitat within any European/Ramsar site would result in a significant effect likely to be more detrimental than any loss of foraging habitat.  Wintering waterbird species (such as Bar-tailed Godwit, Purple Sandpiper, Turnstone, Ringed Plover and Sanderling) may also be affected by any loss of intertidal habitat due to onshore activities, such as cable routeing, associated with the scheme.

6.3.3 The direct loss of seabed habitat may affect all seabird species considered in this assessment due to effects on the availability of their prey; seabirds will be affected most during construction and operation phases.  In advance of any details about exposure levels, birds are considered to have a high sensitivity during these phases.

6.3.4 However, while all species are considered to be of high sensitivity to this risk, sites would only occupy a small proportion of foraging ranges and avoid key feeding areas, therefore the residual significance of such effects would likely be at most medium.

6.4 Physical Loss/Gain of Habitat (Fish Aggregation or Artificial Reef; Impact Pathway 3)

6.4.1 The installation of devices on the seabed, could generate localised new habitat for fish and benthic communities i.e. Fish Aggregation Devices (FADs) or artificial reefs.  This in turn could affect the prey availability in the immediate vicinity of the devices and create new foraging opportunities for diving species.  The extent of this effect is unknown, though it is likely to be small for all species and if it attracts seabirds there may be an increased risk of collision (see Section 6.5). Structures may provide habitat for seabirds, such as gulls and terns, to perch or rest on, or even potential breeding locations.  Species are considered to have a low sensitivity to the creation of new habitat in this manner.

6.5 Physical Damage to Habitat (Reduction in Habitat Quality; Impact Pathway 6)

6.5.1 The potential exists for damage to occur on intertidal and offshore habitats with implications for breeding sites, overwintering areas or foraging habitats.  In advance of any details about the exposure levels the sensitivities of seabirds are considered to be medium to such effects especially during the construction and decommissioning phases when activities on site will be greatest.

6.6 Physical Damage to Species (Collision Risk; Impact Pathway 8)

6.6.1 Seabirds could potentially collide with structures both above and below the sea-surface during surveying, construction, operation and decommissioning of wind turbines.  Collision risk and mortality will depend on a range of factors related to bird species, abundance, foraging modes (e.g. locations and methods), foraging timings (e.g. day or night), topography, weather conditions the value of the area as a feeding ground, the consistency with which it is used for foraging and the nature (especially the underwater mobility) of the structures themselves including the use of lighting for above-surface components[43].  The following sections consider collision risk during the surveying, construction and decommissioning phases and then the operational phase.

6.6.2 Collisions underwater could occur during baseline surveys involving the physical retrieval of samples or bed materials, including borehole surveying or ecological trawl sampling.  There is also a risk of birds colliding above the water with machinery and vessels during the construction phase of all energy sectors, and whilst birds are generally manoeuvrable, they are nonetheless at risk, especially during the night.  Although many breeding birds remain at their nest sites on land at night, some may roost at sea [44].  However, the collision risk with vessels is thought to be minimal, and operational construction vessels pose less threat than commercial shipping due to slow travelling speeds.  The sensitivity of seabirds to collision risk during the surveying, construction and decommissioning is considered to be low.

6.6.3 A number of studies have investigated the collision risks to birds from offshore wind turbines [45] [46] [47] [48] [49] [50] [51]. Many of these studies agree that collision risk is influenced by various factors but is largely driven by the proportion of birds flying at collision risk height [52].

6.6.4 Some bird species are considered to be at a lower risk of collision as they typically fly at low altitudes (above the sea surface and below the swept area of the turbines)[53]. However, other bird species (such as large gulls and Gannets) have a higher potential collision risk, as they typically fly at higher altitudes and travel large distances between breeding and wintering grounds. For example, 35% of Herring Gull flights have been recorded at blade height[54].

6.6.5 Cook et al.[55] found the following species to be particularly prone to collisions with turbines: Northern Gannet, Black-legged Kittiwake, Lesser Black-backed Gull, Herring Gull and Great Black-backed Gull.  The Offshore Renewables Joint Industry Programme (ORJIP) study recorded up to six bird species that collided with turbines: Black-legged Kittiwake, Lesser/Great Black-backed Gull, unidentified large gull and other unidentified gulls[56]. Furness et al.[57], considering both collision and displacement risk, suggested that the key seabird species most affected by offshore windfarm developments included Red-throated Diver, Northern Gannet, Manx Shearwater, Arctic Skua, Great Skua, Lesser-black Backed Gull, Herring Gull, Great Black-backed Gull, Black-legged Kittiwake, Sandwich Tern, Common Tern, Common Guillemot, Razorbill, Atlantic Puffin.

6.6.6 Studies often disagree about the proportions of each species time spent at the ‘collision risk height’. These discrepancies reflect the varying sampling methods used (such as LiDAR and bird tagging) and the factors impacting flight height. Flight height is influenced by various criteria, such as wind speed, wind direction, precipitation, time of the day, season, distance to coast, foraging, habitat type and spatial arrangement, migration, offshore wind farms. Flight height also varies between species and is dependent on a bird’s activity and life-history stage[58].

6.6.7 The other factors that are considered to be important in predicting collision rates include manoeuvrability, bird density, flight speed and flight height distribution [59]. McGregor et al. [60] accounted for dynamic bird speeds (affected by avoidance behaviour) and turbine speeds to enable improved stochastic collision risk models.

6.6.8 Models (in particular the Band model) [61] have been used to estimate collision risk, however, as more empirical datasets have become available, both assumptions and these parameters have been tested. The recent ORJIP study[62], was set up to collect data on seabird collision and avoidance rates at an operational wind farm. The study concluded that collision risk is likely to be lower than some previous studies and models have estimated.

6.6.9 Other research concurs with the ORJIP study, suggesting that birds adapt their flight paths to avoid collision with turbines[63] with generally very high avoidance of turbines exhibited by seabirds [64]. WWT [65] have shown that most seabirds are not expected to be at risk because of these avoidance rates. While work by Cook et al.[66] suggested that birds rarely pass close to the rotor blades.

6.6.10 However, changing behaviour presents other challenges and risks to birds, in the following ways: firstly, by avoidance (of the area covered by windfarms, turbines or blades) birds are displaced from their normal habitat (habitat loss), and secondly, by barrier effects, where they adapt their behaviour, thus increasing flight times and losing energy[67]. The potential effects from these non-physical impacts are considered below.

6.6.11 At this time the sensitivity of seabirds to collision risk during the operational phase is considered to be medium; however, it is acknowledged that this is a developing area of research with several recent studies indicating a much greater avoidance behaviour than has previously been assumed and/or modelled. In addition, further details on exposure levels will be needed to fully understand site-specific risk levels.  Sensitivities at a population-level are also likely to be inherently lower than for individuals.

Species sensitivities to collision risk

6.6.12 All species scoped into this assessment are at some risk of collision during the survey, construction, operation, and decommissioning phases but this will vary according to the nature of the environment, and species foraging modes.

6.6.13 Those species which forage during dusk/dawn or at night are possibly at a greater risk from collision with wind turbines than those who forage during daylight hours, albeit that the impact of foraging period on sensitivity is less than the impact of flight height (Table 8). Shag, for example, forage only during daylight, whereas a proportion of foraging activity of Guillemots and Razorbills occurs around dawn and dusk [68] [69] [70] [71].  Manx Shearwaters and both UK petrel species arrive at breeding burrows overnight, thus travelling at sea overnight, and potentially increasing collision risk.  This may be further exacerbated by their low flight height.

6.6.14 Overall, it is generally agreed that the large gulls such as Great Black-Backed Gull, Herring Gull and Lesser Black-Backed Gull as well as Northern Gannet and Black-legged Kittiwake are the most sensitive to the risk of collision mortality [72] [73].  These species all tending to spend a comparatively higher proportion of their flying time at an altitude that overlaps with blade height [74].

6.6.15 Collision rates are variable and while an accurate quantitative understanding about the impacts is not possible, Collision Risk Modelling (CRM) tools (e.g. Band model) have been extensively used for both onshore and offshore sites globally, including a range of UK offshore developments e.g. DECC[75]. These models can provide useful numerical predictions but as they are dependent on the parameters and avoidance rate for individual species, they need to be specific to developments. The models are also highly sensitive to assumptions on avoidance rates which, as some recent studies suggest, may be higher than previously thought [76] [77].

6.6.16 Avoidance can occur at various stages of the flightpath, including macro, meso or micro scales: Macro-scale responses are behavioural responses to the presence of the windfarm, occurring at distances greater than 500 m from the base of the outermost turbines. Meso-scale responses are responses to individual turbines occurring between the base of each turbine and the windfarm perimeter (defined as 500 m from the base of the outermost turbines). Micro-scale avoidance is the ‘last-second’ action taken to avoid collision, which is considered to occur within 10 m of the turbine rotor blades[78].

6.6.17 Bird avoidance is mainly thought to occur at the meso-scale[79] [80]. In contrast, very few birds are thought to fly close enough to turbines to require micro-avoidance behaviour [81] [82] [83] [84].

6.6.18 Whilst Bowgen and Cook [85] have recommended updated collision factors to the Band model, they also suggest that the best model available is still the Band model. This is because the impact of windfarms varies according to such factors as the different seabird species present, their distribution, the geographical area and the time of year, in addition to many other variables.

6.6.19 Bowgen and Cook [86] emphasise the importance of site-specific data (e.g. distribution of key species) and behaviours exhibited during the breeding season in determining the true risk to bird species. It has been suggested that bird avoidance rates may be lower during the breeding season[87].

6.6.20 The distribution of seabird species is determined by density‐dependent competition, habitat accessibility and coastal geometry, and habitat availability. For example, Kittiwakes are generally found in offshore waters, tending to forage over long distances (tens to hundreds of kilometres from their colonies) [88].

6.6.21 Vanermen et al.[89] showed how seabirds react differently to windfarms: BACI studies in a Belgian offshore windfarm suggest that Northern Gannet, Common Guillemot and Razorbill avoid the windfarm area whereas, Lesser Black-backed Gull and Herring Gull were attracted to the windfarm and their abundance increased. Similarly, the Common Gull, Black-legged Kittiwake and Great Black-backed Gull also frequented the wind farm.

6.6.22 The migratory and foraging behaviour of many bird species makes assessment of collision risk difficult. Identifying distinct flyway paths is complex both because of the nature and limitations of available information and because movements are likely to occur across broad fronts rather than along clearly definable routes.  Variables involved in flight direction include:

  • Spatial variation in food abundance (including anthropogenic factors such as fishing vessels);
  • The risk of predation/kleptoparasitism by other bird species;
  • The importance of nest attending to incubate eggs and protect the nest from predators; and
  • Weather and climatological factors.

6.6.23 The RSPB is currently progressing research to map the variation in seabird collision risk around the UK for at least one priority seabird species (Kittiwake). The project will take account of how behaviour affects collision risk and combine this with population modelling to estimate which seabird colonies within SPAs are most at risk from existing developments. Also, those areas where new development would have the greatest (and lowest) impacts on the species in question will be identified. Although the RSPB project is not due for completion until autumn 2019, the RSPB will seek to provide relevant outputs from their study to assist with the plan-level HRA as it progresses through the Iterative Plan Review process (see Section 11).

6.6.24 A literature review encompassing inter alia foraging behaviour, was carried out (Appendix G). The results of the FAME (The Future of the Atlantic Marine Environment) study programme indicate the variability of foraging routes and feeding sites.  For example, Northern Gannets have been observed repeatedly foraging over a narrow range of bearings in the North Sea.  Conversely, in the Celtic Sea birds from a smaller site did not exhibit this behaviour.  It was concluded that differences in the consistency of foraging locations were mainly related to differences in the spatial and temporal predictability of prey resources in the two study areas [90].

6.6.25 As highlighted by Bowgen and Cook[91], a fuller understanding of bird collision risk requires site-specific data to inform models and the assessment. Although generic data on bird sensitivities provides a starting point, the potential collision risk to seabirds cannot be fully realised without additional baseline data specific to the proposed location.

Lighting

6.6.26 Lighting has the potential to influence the risk of seabird collision with devices.  In particular, this issue has been given a lot of consideration as part of investigations into the collision risk posed by tall wind turbines (>200m) where the above-water collision risk is clearly much greater. Early work carried out by [92] found that lights on tall communication towers attracted migratory birds which often resulted in collision.  A more recent study also found strong positive link between lighting and collision rate [93].  Therefore, it has been concluded that offshore wind turbines, when lit at night, could pose a risk that is similar to communication towers [94].

6.6.27 Navigational lighting has also been identified as having the potential to increase collision risk. Studies of different species have indicated that altering the type of lighting (e.g. flashing/strobing) and/or the light’s colour spectrum can reduce the risk of attracting birds and therefore reduce such collision risks.

6.7 Non-Physical Disturbance (Noise/Visual Disturbance Causing Exclusion Effects; Pathways 9, 10,11 and 13)

6.7.1 Wind turbines could create a barrier effect to birds, resulting in deviations in their flight route to avoid the structures [95].  Griffin et al. [96] observed birds apparently exhibiting avoidance behaviour near operational wind farms at Robin Rigg and Barrow by increasing flight height.

6.7.2 At Nysted offshore wind farm in the western Baltic, radar studies have indicated a high degree of avoidance by Eider and other large waterbirds during migration[97].

6.7.3 An output from this work is shown below (Image 1), the black lines indicate migrating waterbird flocks and the red dots indicate the wind turbines. There was a significant reduction in migration tracking densities within the wind farm area post-construction [98].  During this study avoidance response differences were also observed during daylight and at night.  Nocturnally migrating waterfowl over Denmark and the Netherlands have also been observed to detect and avoid turbines, with avoidance distances greater during darker nights [99] [100].

Image 1: Westerly oriented flight trajectories during the initial operation of the wind turbines at Nysted Offshore Wind Farm (scale bar indicates a distance of 1km). Source: Desholm and Kahlert[101]

Image 1: Westerly oriented flight trajectories during the initial operation of the wind turbines at Nysted Offshore Wind Farm (scale bar indicates a distance of 1km). Source: Desholm and Kahlert

6.7.4 Following construction of an offshore wind farm site at Tunø Knob in the Danish Kattegat, the number of Common Scoters and Eiders decreased in the two years following construction. However, Eider numbers subsequently increased, possibly due to birds habituating to the wind farm or as a result of the increased abundance of mussels [102]. Later work found that Eider reacted strongly to the presence of wind turbines, interpreted to be a consequence of this species’ high-flying speed and low manoeuvrability [103].

6.7.5 Following construction of Horns Rev Offshore Wind Farm aerial surveys found that divers, Guillemots, Gannets, Razorbills and Common Scoters all occurred in lower numbers than expected in the wind farm area following construction. Conversely, gulls and terns showed a preference for the wind farm area following construction [104]. Again, it is recognised that these changes may reflect habituation to wind turbine presence or may be as a result of changes in food availability rather than displacement by disturbance [105].

6.7.6 Little is known about the sensitivity of bird species to barrier effects and their ability to alter flight heights.  However, avoidance behaviour may lead to the possibility of increased energy expenditure when birds fly further or higher to avoid large turbines. This may potentially disrupt linkages between distant feeding, breeding, moulting and roosting areas which otherwise would be unaffected.

6.7.7 Noise disturbance may occur during the pre-construction survey work (seismic exploration, geophysical surveys), construction/decommissioning (installation/removal of cables and turbines, vessel movements) and turbine operation.  The extent to which birds are affected by sources of noise and visual disturbance has been the subject of a lot of previous research and monitoring work;

6.7.8 Studies generally show that birds are disturbed by a sudden large noise but have the ability to habituate (become accustomed) to regular noises.  For instance, with respect to piling specifically, it has been concluded that although piling is often the noisiest construction activity, it often consists of rhythmic “bangs”, which, after a short period, birds can become accustomed to [106].  Other research has also indicated that in general, birds appear to habituate to continual noises as long as there is no large amplitude ‘startling’ component [107].

6.7.9 The ABP Teignmouth Quay Development estimated an approximate zone within which birds may be affected by disturbance from construction works (piling and dredging) to be typically about 200m [108].  The startling effects of sudden noise were quantified, based on published research, by the Environment Agency for the Humber Estuary Tidal Defences scheme.  It was concluded that a sudden noise in the region of 80dB appears to elicit a flight response in waders up to 250m from the source, with levels below this of approximately 70dB causing flight or anxiety behaviour in some species.

6.7.10 Drilling/piling activity during preliminary surveys and construction could disrupt seabird foraging and directly affect the senses of species diving underwater for prey.  Seabirds hunt visually underwater, but evidence from on land suggests they may also have acute hearing, and thus marine noise could potentially disorientate and upset foraging rhythms and even damage hearing.

6.7.11 Little is known concerning the sensitivity of species to marine noise and thus it is not fully possible to assess the likelihood or magnitude of noise effects at any phase of the scheme.  However, diving species are probably at greater risk and hence provisionally considered to be of medium sensitivity as compared to a lower sensitivity for surface-feeders.

6.7.12 As a result of disturbance, birds may avoid habitat during the pre-construction survey, construction, operation and decommissioning phases of a wind farm development.  Exclusion from habitats essentially prevents access to prey sources.  Such exclusion could reduce other effects, notably collision mortality.  However, reductions in the availability of habitat and access to prey could lead to many changes in the way individuals forage, including increased individual stress levels and alterations to individual time budgets owing to further foraging distances [109].

6.7.13 Although alternative foraging areas may exist, the quality of the foraging habitat that species are forced to use may be lower, as well as more distant, thus increasing foraging time required to meet energetic needs.  Species may have little flexibility to alter their time budgets to encompass extra foraging/travel to destinations.  Species may also be reliant on a particular prey source at a location and may have less ability to switch to a different prey source.  Effects at the colony and nest sites would be experienced through a reduced attendance time (due to lower feeding rates of chicks and longer foraging trips), possibly with increased neglect of chicks increasing predation risk or attacks from conspecifics.  Furthermore, reduction in available habitat can generate increased competition to find food with knock-on implications for neighbouring areas (i.e. not included in the assessment).  These disturbances may, therefore, cause a reduction in foraging success, decreases in breeding success, and effects on individual fitness.

6.7.14 All seabird species screened into the assessments are at some risk of disturbance from the indirect loss of foraging habitat although it is clearly the case that this is dependent upon foraging locations used by different species (i.e. whether they feed on intertidal or offshore locations) and the area of development activity.  In general, the effects will be temporary during initial survey phases, causing minimal disruption.  However, more significant effects may occur in the construction, operation and decommissioning phases.

6.7.15 The effect that these changes have on birds will depend on how flexible the species are at coping with changes, those species that tend to feed on very specific habitat features will be the most sensitive.  For instance, Garthe and Hüppop [110], and more recently Marine Scotland [111], evaluated the sensitivity of species to offshore wind farms, and their score for flexibility in habitat use provides a useful measure to the sensitivity of species to this effect.  As suggested by evidence from offshore wind farms, Red-throated Divers and Common Scoters (both diving species) may be particularly sensitive to disturbance and thus the effects of indirect habitat loss.

6.7.16 The breeding success of some surface-feeding species, such as Terns and Kittiwakes, is negatively affected by changes in food availability due to reliance of prey brought to the sea surface [112]. This indirect effect has been presented in Perrow et al. [113], which suggests that Little Tern breeding success at a colony in Norfolk may have been reduced by a shortage of young herring around Scroby Sands offshore wind farm; considered a result of monopile installation affecting local fish reproduction.

6.7.17 Those species with higher energy cost burdens of flight and foraging (such as auks) may find it harder to increase foraging ranges to more distant prey resources, as compared to species such as Gannets that are generally less sensitive to natural changes in the availability of food and can forage over a much wider area.  Diving species with high wing loading have high energetic costs during flight, thought to be linked with adaptation of wings for underwater locomotion [114] [115].  Thus, while they have the potential to forage far from colonies, their typical ranges may be smaller than those of other species, i.e. 20-40 km [116] [117], and may be less flexible in making changes in the event of reduced prey availability [118].  In summary, seabirds are considered to have a medium sensitivity to the effects of exclusion from feeding areas.

6.7.18 The effect of disturbance and habitat exclusion during construction will depend on the extent of construction, as well as the time of year; a potential mitigation measure is to avoid construction at key times of year (i.e. immediately before and during the breeding season) when prey is needed by adult birds and their young.

6.7.19 In general, disturbance to birds can affect feeding and roosting behaviour, with possible long-term effects of repeated disturbance including loss of weight, condition and a reduction in reproductive success.  The effect of such disturbance is linked to the number of disturbance occurrences and the status of the conditions that are prevalent.

6.8 Toxic Contamination (Contamination and Spillages; Pathways 14 and 15)

6.8.1 Spillage of oils and fluids from construction vessels and machinery into the marine environment could adversely affect sediment or water quality during all phases of wind farm development.  Marine birds are particularly sensitive to contamination by oil [119], as the oil can cause considerable damage to water-proofing and affect flight [120], as well as additional physiological damage if ingested.

6.8.2 The sensitivity of species to oil contamination is considered to be medium during construction, operation, and decommissioning, but a lower risk during pre-construction surveys, and is dependent on the general behaviour and distribution of species (e.g. the proportion of time spent on the sea surface relative to flying or feeding locations).  Auks, in particular, may spend a considerable amount of time on the sea surface or foraging [121], and thus have a higher risk of being adversely affected by ‘at sea’ spillages of contamination events [122].  By contrast waders would only be affected by contamination events that affect their intertidal foraging zones.

6.8.3 Ingestion of contaminated sediments either through direct poisoning or bio-magnification of pollutants as a result of ingestion of contaminated prey would increase the probability of mortality of all species being considered.  The precise risk would again depend on the use of the area by foraging seabirds.  All species are potentially sensitive to this effect, but it is considered most relevant to diving birds. The overall sensitivity to toxic contamination is low during the construction and decommissioning phases.

6.9 Non-toxic Contamination (Increased Turbidity; Impact Pathway 16)

6.9.1 Activities involved during the construction and decommissioning of wind devices and associated cabling (e.g. use of jack-up legs, piling activities and cable installation) may result in an increase in suspended sediments and turbidity, potentially leading to effects on (diving) seabird foraging success and predator-prey interactions.  The extent of any effect will be determined by the environment itself, i.e. by the strength of currents dispersing the sediment and background suspended sediment levels.  The nature, scale and location of the structures will be the key determinants of the risk and magnitude of the effect.

6.9.2 In addition to changes in turbidity, there will also be a change in hydrodynamic regime around any device that may affect diving seabirds.  Fish are attracted to areas of high flow gradients and fronts.  Thus, a change in local turbidity and flow of currents during all phases of construction may influence the distribution of prey resources for all diving seabird species resulting in change of use of an area.

6.9.3 Species diving underwater are at greatest risk of having foraging activity disrupted by sediment mobilisation and suspension, and this is most likely to occur during the construction and decommissioning phases.  Diving species such as Auks, Shags and Cormorants use much of the water column and thus are considered to have a medium sensitivity to this effect, whereas surface-feeding seabirds are considered to have a low sensitivity.  All species, however, are at risk of disruption due to likely prey avoidance of areas that have been disturbed.  All species are also at medium risk from changes to prey distribution areas associated with changes in hydrodynamics.  Nevertheless, given the dispersive nature of the marine environment in areas where offshore wind development will occur, the sensitivities of species to this effect are considered to be low.

6.10 Bird Sensitivity Review

6.10.1 Table 9 shows the sensitivities of qualifying bird interest features species to the activities associated with the draft Plan.  Some of the highest risks are associated with habitat loss, reduced foraging area and disturbance.  The levels of risk will be different depending upon the life history and foraging behaviour of the species in questions.  This level of risk for different species is indicated within Table 9.

6.10.2 To provide an indication of which bird species are at risk from different project components, the screening schedules for each of the 17 DPOs (Tables D1-D17) include a reference to the general location of key species (i.e. whether they are landward, intertidal or offshore).

Table 9. Potential sensitivities of bird interest features to the draft Plan

Sensitivity Category Sensitivities Pathway Ref. No. Leasing Activity as Identified in Sectoral Offshore Wind Plan HRA (Summary Impact Pathway Description) Survey Construction Operation Decommission
PLG Physical Loss/Gain of habitat  2 Loss of foraging areas from reduction in coastal and offshore habitat due to installation of devices and cable armouring both at the development footprint and outside these areas from associated scour and indirectly from changes to the hydrodynamic regime as well as from chains anchoring devices disturbing seabed habitat during operation. [Applies to all seabirds] No impact  No impact  LMS No impact 
PLG Physical Loss/Gain of habitat 3 Presence of structures on seabed for the duration of the project resulting in changes to prey and species behaviour (e.g. acting as FAD (Fish Aggregating Device), artificial reef or bird roost). [Diving birds and surface feeding birds are most sensitive] No impact  No impact  LS No impact 
PD Physical damage to habitat 6 Reduction in quality of foraging areas as result of damage to coastal and offshore habitat from baseline surveys (e.g. boreholes and trawls); from equipment use causing abrasion, damage or smothering during installation; from maintenance and removal of cables/devices or from scour, sediment transport and hydrodynamic change during operation. [Applies to all seabirds] LS MS LS MS
PD Physical damage to species 8 Collision risk and possible mortality of seabird species due to the presence of devices or from vessels travelling to and from the site ((including above and below water collision risk and the influence of lighting) [Nocturnal seabird species especially sensitive] LS LS MS LS
NPD Non-physical disturbance 9 Presence of structures or disturbance (noise or visual) resulting in a barrier to movement, migratory pathways and/or access to feeding grounds depending on array design [Applies to all seabirds] No impact  No impact  LMS No impact 
NPD Non-physical disturbance 10 Visual disturbance and exclusion from areas as a result of surveying, cable and device installation/operation and decommissioning activities and movements of vessels. [Applies to all seabirds although surface feeding and diving birds most sensitive to at-sea activities] LS MS LMS LMS
NPD Non-physical disturbance 11 Noise/vibration disturbance and exclusion from areas as a result of vessels and other activities during survey work (e.g. seismic exploration and geophysical surveys), construction (e.g. piling, drilling, cable laying), operation (e.g. device noise), maintenance or decommissioning.[Applies to all seabirds] LS LMS LMS LMS
NPD Non-physical disturbance 13 Presence of structures resulting in an exclusion/displacement of a species from the area. [Applies to all seabirds]  No impact LS MS LS
TC Toxic Contamination (Reduction in water quality) 14 Spillage of fluids, fuels and/or construction materials during installation or removal of structures (devices and cables) or during survey/maintenance. [Highest sensitivities for diving seabirds] LS MS LMS LMS
TC Toxic Contamination (Reduction in water quality) 15 Release of contaminants associated with the dispersion of suspended sediments during installation or removal of structures (devices and cables). [Highest sensitivities for diving seabirds] No impact  LS No impact  LS
NTC Non-toxic Contamination (Elevated turbidity) 16 Increase in turbidity associated with the release of suspended sediments during installation or removal of structures (devices and cables). [Highest sensitivities for diving seabirds] No impact    No impact   
In this table, only the estimated sensitivity levels are shown. The level of risk will be dependent upon exposure.  For instance, there would be a high degree of exposure for seabirds were a development to occur within or near to a European/Ramsar site.  However, at the present time, there is uncertainty regarding the degree of exposure and a worst-case assumption has been made.
LS: Low Sensitivity
LMS: Low to Medium Sensitivity
MS: Medium Sensitivity
HS: High Sensitivity

6.11 Potential Effects on European/Ramsar Sites from the Sectoral Offshore Wind Plan

6.11.1 On the basis of the sensitivities of the relevant interest features the following sections review the typical conservation objectives for these features and the potential effects arising for each of the European/Ramsar sites. Although conservation objectives for yet to be designated pSPAs have still to be agreed, the draft objectives available indicate that the generic objectives outlined below would encompass these sites. It is, however, recognised in the case of Seas off Foula pSPA and Seas off St Kilda pSPA that the function of the pSPAs as foraging areas means that consideration of foraging distances from the sites is not required (i.e. foraging distances are only required when considering sites designated for bird colonies).

6.11.2 The conservation objectives for the qualifying bird interest features seek to avoid deterioration of the habitats of the qualifying species or significant disturbance to the qualifying species, thus ensuring the integrity of the site.  The conservation objectives are to ensure for the qualifying habitats that the following are maintained in the long term:

  • Population of the species as a viable component of the site;
  • Distribution of the species within site;
  • Distribution and extent of habitats supporting the species;
  • Structure, function and supporting processes of habitats supporting the species; and
  • No significant disturbance of the species.

6.11.3 Taking account of the conservation objectives and the plan-level activities to which the key interest features (all bird qualifying features within the SPA/Ramsar sites) are sensitive, this section reviews the potential effects of the draft Plan on the integrity of the European/Ramsar sites.  The results are presented in Table 10.

Table 10: Assessment of the potential effects of the Sectoral Offshore Wind Plan on the bird features of relevant European/Ramsar sites

Screened-in sites with these qualifying features are provided in Table C1 (Appendix C) Is There an Adverse Effect on Integrity of any European/ Ramsar sites
Is There an Adverse Effect on Integrity
Following Application of Mitigation Measures?
Qualifying and Supporting Feature Summary Impact Pathway  Pathway Ref. No. Sensitivity Level(s) Commentary, and Relevant Conservation Objective
  • All seabird species
Physical loss/gain of habitat Loss of foraging areas from reduction in coastal and offshore habitat due to installation of devices and cable armouring both at the development footprint and outside these areas from associated scour and indirectly from changes to the hydrodynamic regime as well as from chains anchoring devices disturbing seabed habitat during operation. 2 Sensitivity Level(s) maximum considered to be low to medium (see Table 9 for detail and colour code)   Possibility of an adverse effect on integrity Further work would be required at project-level to ascertain LSE. However, in advance of considering mitigation measures, it cannot be concluded that there will be no AEOI on any European/Ramsar sites. This is because of the inherent uncertainties such as:
  • the detail of the Plan implementation process;
  • future generation capacities;
  • the location, scale and densities of development;
  • the proposed technologies to be used and future advances in these technologies;
  • the scale of the effects arising via some of the defined impact pathways; and
  • the efficacy of some project-level mitigation options.
No adverse effect on integrity With the application of appropriate and meaningful mitigation measures to accompany the Plan (see Section 11), there will be no AEOI.
Commentary/ Review All seabird species are considered sensitive to this effect over the operational phase of the wind farm.  However, the effect will depend on the quality and location of habitat that might be affected e.g. loss of sandy sediments found within the DPOs may have the greatest effect on seabirds due to their importance for sandeels, and loss of intertidal habitat due to cable installation works could potentially affect foraging areas for over-wintering birds. 
Relevant Conservation Objectives (see Section 6.11 All of the 5 objectives are pertinent of which the following are considered to be most relevant:
  • Distribution and extent of habitats supporting the species; and
  • Structure, function and supporting processes of habitats supporting the species.
All seabird species Physical Loss/Gain of habitat Presence of structures on seabed for the duration of the project resulting in changes to prey and species behaviour (e.g. acting as FAD (Fish Aggregating Device), artificial reef or bird roost). 3 Sensitivity Level(s) considered to be low (see Table 9 for detail and colour code) As above As above
Commentary/Risk Review Underwater structures may provide new foraging opportunities for diving species. Construction of wind farm arrays and structures above water that have a stable platform may serve as additional resting and/or breeding habitat especially for gulls and terns. The extent of this (positive) effect and the degree to which it then has consequences for increased risk through collision etc is unknown, though sensitivity likely to be low.
Relevant Conservation Objectives (see Section 6.11 All of the 5 objectives are pertinent of which the following are considered to be most relevant:
  • Distribution and extent of habitats supporting the species; and
  • Structure, function and supporting processes of habitats supporting the species
  • All seabird species
Physical damage to habitat Reduction in quality of foraging areas as result of damage to coastal and offshore habitat from baseline surveys (e.g. boreholes and trawls); from equipment use causing abrasion, damage or smothering during installation; from maintenance and removal of cables/ devices or from scour, sediment transport and hydrodynamic change during operation. 6 Sensitivity Level(s) considered to be low or medium (see see Table 9for detail and colour code) As above As above
Commentary/ Review All species are considered to be of low or medium sensitivity with the higher sensitivities occurring during the construction and decommissioning phases.  However, the effect will depend on the quality and location of habitat that might be affected e.g. loss of sandy sediments found within the DPOs may have the greatest effect on seabirds due to their importance for sandeels, and loss of onshore habitat due to cable installation works could potentially affect breeding and/or wintering birds.
Relevant Conservation Objectives (see Section 6.11 All of the 5 objectives are pertinent of which the following are considered to be most relevant:
  • Distribution and extent of habitats supporting the species; and
  • Structure, function and supporting processes of habitats supporting the species
  • All seabird species
Physical damage to species Collision risk and possible mortality of species due to the presence of devices or from vessels travelling to and from the site ((including above and below water collision risk and the influence of lighting) 8 Sensitivity Level(s) considered to be medium (see Table 9for detail and colour code) As above As above
Commentary/ Review Wind turbines can create a barrier effect with birds potentially deviating their flight route to avoid the structures. Evidence of birds exhibiting avoidance behaviour by increasing flight height has been obtained near operational wind farms at Robin Rigg and Barrow.  Those seabirds that fly and forage during the night are considered to have a medium sensitivity to collision risk.  Diurnally foraging species can be considered to have a low sensitivity to the risk of collision mortality
Relevant Conservation Objectives (see Section 6.11 For the purposes of this assessment, the overarching conservation objective for all the SPAs and Ramsar sites reviewed and all the impact pathways/activities assessed is to “maintain specific reference populations for feature species, as provided in the relevant citations”.  This has been applied because it covers impacts to both the species and the habitats that support them, and it encompasses all of the five 5 conservation objectives that are common to all SPAs.
  • All seabird species
Non-physical disturbance Presence of structures and disturbance (noise or visual) associated with devices presenting a barrier to movement and block migratory pathways or access to feeding grounds depending on array design 9 Sensitivity Level(s) considered to be low to medium (see see Table 9 for detail and colour code) As above As above
Commentary/Risk Review Little is known about the sensitivity of bird species to barrier effects and their ability to alter flight heights.  However, avoidance behaviour may lead to increased energy expenditure when birds fly further or higher to avoid turbines, which may potentially lead to the disruption of linkages between distant feeding, breeding, moulting and roosting areas which otherwise would be unaffected.
Relevant Conservation Objectives (see Section 6.11 All of the 5 objectives are pertinent to the potential effects; however, the following are considered to be most relevant:
  • Distribution of the species within site;
  • Distribution and extent of habitats supporting the species; and
  • Structure, function and supporting processes of habitats supporting the species.
  • All seabird species
Non-physical disturbance Visual disturbance and exclusion from areas as a result of surveying, cable and device installation/operation and decommissioning activities and movements of vessels. 10 Sensitivity Level(s) considered to be low to medium (see see Table 9 for detail and colour code) As above As above
Commentary/Risk Review There are potential effects during surveying and cable and device installation, lesser effects are likely during operation and decommissioning. The greatest disturbance is likely to be caused by human presence.  These disturbance effects can lead to displacement of seabirds.
Relevant Conservation Objectives (see Section 6.11 All of the 5 objectives are pertinent to the potential effects; however, the following are considered to be most relevant:
  • Distribution of the species within site; and
  • No significant disturbance of the species;
  • All seabird species
Non-physical disturbance Noise/vibration disturbance and exclusion from areas as a result of vessels and other activities during survey work (e.g. seismic exploration and geophysical surveys), construction (e.g. piling, drilling, cable laying), operation (e.g. device noise), maintenance or decommissioning 11 Sensitivity Level(s) considered to be low to low/medium (see see Table 9 for detail and colour code) As above As above
Commentary/Risk Review There are potential effects during cable and device installation, operation and decommissioning with lesser effects during the pre-construction survey phase. The sensitivity of birds to airborne noise during construction is considered to be low/medium given their ability to habituate to continual noises (e.g. piling). The sensitivity of species to underwater marine noise is unknown, but likely to be greater for diving species and sea surface foragers. There is potential for displacement of sea birds as a result of noise/vibration disturbance.
Relevant Conservation Objectives (see Section 6.11 All of the 5 objectives are pertinent to the potential effects; however, the following are considered to be most relevant:
  • Population of the species as a viable component of the site;
  • Distribution of the species within site;
  • No significant disturbance of the species; and
  • Structure, function and supporting processes of habitats supporting the species.
  • All seabird species
Non-physical disturbance Presence of structures resulting in an exclusion/displacement of a species from the area. 13 Sensitivity Level(s) considered to be medium (see see Table 9 for detail and colour code) As above As above
Commentary/Risk Review Exclusion/displacement from foraging areas may result in increased energy burdens on seabirds. It is considered that surface feeding species will have a low sensitivity as compared to a medium sensitivity for diving birds.

Relevant Conservation Objectives (see Section 6.11 All of the 5 objectives are pertinent to the potential effects; however, the following are considered to be most relevant:

  • Distribution of the species within site;
  • Distribution and extent of habitats supporting the species; and
  • Structure, function and supporting processes of habitats supporting the species.
  • All seabird species
Toxic Contamination (Reduction in water quality) Spillage of fluids, fuels and/or construction materials during installation or removal of structures (devices and cables) or during survey/maintenance. 14 Sensitivity Level(s) considered to be low to medium (see see Table 9 for detail and colour code) As above As above
Commentary/ Review For all stages of the work from the construction to decommissioning and including operational/maintenance works, there is the potential for accidental discharges/spillages from machinery and vessels. All species, including those using intertidal habitats have a medium sensitivity to the effects from this impact pathway. However, adoption of standard safety measures would be employed throughout all phases of the project to reduce likelihood of this occurring.
Relevant Conservation Objectives (see Section 6.11 All of the 5 objectives are pertinent to the potential effects; however, the following are considered to be most relevant:
  • Distribution of the species within site;
  • No significant disturbance of the species; and
  • Structure, function and supporting processes of habitats supporting the species.
  • Diving Species
Toxic Contamination (Reduction in water quality) Release of contaminants associated with the dispersion of suspended sediments during installation or removal of structures (devices and cables) . 15 Sensitivity Level(s) considered to be low (see see Table 9 for detail and colour code) As above As above
Commentary/Risk Review Where cable routeing passes through areas of contaminated sediment, remobilisation of contaminants may occur. This impact pathway is considered a low risk to seabirds with the potential to occur during the construction and decommissioning phases.
Relevant Conservation Objectives (see Section 6.11 All of the 5 objectives are pertinent to the potential effects; however, the following are considered to be most relevant:
  • Distribution of the species within site;
  • No significant disturbance of the species. and
  • Structure, function and supporting processes of habitats supporting the species.
  • All seabird species
Non-toxic Contamination (Elevated turbidity) Increase in turbidity associated with the release of suspended sediments during installation or removal of structures (devices and cables). 16 Sensitivity Level(s) The risks are considered to be low (see see Table 9 for detail and colour code) As above As above
Commentary/ Review Increases in suspended sediment during the construction and decommissioning phases may disrupt foraging and predator-prey interactions.
Relevant Conservation Objectives (see Section 6.11 All of the 5 objectives are pertinent to the potential effects; however, the following are considered to be most relevant:
  • Distribution of the species within site;
  • No significant disturbance of the species; and
  • Structure, function and supporting processes of habitats supporting the species.

Contact

Email: drew.milne@gov.scot