Identifying a Range of Options to Prevent or Reduce Avian Collision with Offshore Wind Farms using a UK-Based Case Study

Report

Title: Identifying a Range of Options to Prevent or Reduce Avian Collision with Offshore Wind Farms using a UK-Based Case Study

Author:

Cook, A.; Ross-Smith, V.; Roos, S.; Burton, N.; Beale, N.; Coleman, C.; Daniel, H.; Fitzpatrick, S.; Rankin, E.; Norman, K.; Martin, G.

Publication Date:

May 1, 2011

Document Number:

580

Pages:

199

Publisher:

British Trust for Ornithology

Affiliation

British Trust for Ornithology (BTO), University of Birmingham

Sponsoring Organization:

UK Department for Environment Food and Rural Affairs (DEFRA)

Technology:

Wind Energy, Fixed Offshore Wind

Receptor:

Birds

Document Access

Website:

External Link

Attachment:

Access File
Notice: This material may be protected by Copyright Law.

Citation

Cook, A.; Ross-Smith, V.; Roos, S.; Burton, N.; Beale, N.; Coleman, C.; Daniel, H.; Fitzpatrick, S.; Rankin, E.; Norman, K.; Martin, G. (2011). Identifying a Range of Options to Prevent or Reduce Avian Collision with Offshore Wind Farms using a UK-Based Case Study (Report No. 580). Report by British Trust for Ornithology (BTO). Report for UK Department for Environment Food and Rural Affairs (DEFRA).

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Abstract

This project aims to review and evaluate potential mitigation options for preventing or reducing avian collisions with offshore wind farms. Offshore wind farms may potentially affect bird populations through the displacement of birds due to the disturbance associated with developments, the barrier they present for migrating birds and birds commuting between breeding sites and feeding areas, habitat change or loss and through collision mortality.
The work has four main objectives: i. To review current avian collision mitigation options, both national and international; ii. To identify existing and novel mitigation methods that could be used to minimise avian collision; iii. To identify which bird species, native and migratory (including breeding units and breeding / overwintering populations), are considered most at risk in UK waters, with the view to identifying key species for cumulative assessment; iv. To model the cumulative risk of avian collision in wind farms and, where sufficient information exists to parameterise the models, model this risk against a range of mitigation options to determine which is most successful, using the Greater Wash as a UK case study.
A range of technologies and techniques have been proposed to reduce bird collisions within different sectors. Few have been tested extensively on either onshore or offshore wind farms. In the UK, the majority of measures implemented to reduce collision rates relate to the siting, orientation and spacing of turbines. Ten novel measures were selected for further analysis. These were evaluated in the context of their technical feasibility, implementation and operational costs and effectiveness in reducing the risk of bird collision rates. This evaluation is summarised below.
The risk or vulnerability of species to the effects of developments, such as offshore wind farms, reflects the combination of both species’ sensitivities and exposure to these effects. In this review, we thus first consider which UK species are likely to be most sensitive to the effect of collision mortality with offshore wind farms in UK waters, before then considering which species might be exposed to this effect as a result of Round 1 and 2 developments, potential Round 1 and 2 extensions, Round 3 sites, and sites planned for Scottish Territorial Waters.
Three previous studies have appraised the sensitivities of bird species to the effects associated with offshore wind farms. Garthe and Hüppop (2004), and King et al. (2009) which follows that study, determined a Species Sensitivity Index (SSI) considering aspects relating to all the potential effects posed by offshore wind farms. Langston (2010) used a three-level categorical system to define species’ sensitivities to ‘Collision risk’, ‘Displacement’, ‘Barrier’, and ‘Habitat/Prey’ effects, and a score for species’ conservation status, and from these scores derived a species-specific value for ‘Overall Risk’.
Comparison of the scores related to collision risk from these studies reveals a good level of accord. Given this close correlation, we defined the species that are sensitive to the effect of collision mortality with offshore wind farms in UK waters as those having High or Moderate Collision Risk scores according to Langston (2010). This provided a total of 31 species or species’ populations (17 seabird species, 13 wildfowl species or species’ populations and one terrestrial species).
For the 17 seabird species sensitive to the effect of collision mortality with offshore wind farms in UK waters, we produced maps showing the species’ foraging ranges from SPAs and their at-sea-distributions (from European Seabirds at Sea data) showing their exposure to offshore wind farms (Figures 3.3.3 to 3.3.34).
Whether due to their foraging ranges from SPAs, or due to their presence in wind farm development zones at times of year that these species are not associated with SPAs, or due to their migration routes, all 31 sensitive species are potentially exposed and thus should be considered vulnerable to the risk of collision with Round 1 and 2 developments, potential Round 1 and 2 extensions, Round 3 sites, or sites planned for Scottish Territorial Waters. However, six species – the Greylag Geese and Corncrake which breed in northwest Scotland, and Pomarine Skua, Long-tailed Skua, Iceland Gull and Glaucous Gull which are only present in UK waters in small numbers – probably face limited exposure to offshore wind farm development zones and should thus be considered to be less vulnerable to collision mortality. Effects on other species, such as the waders and wildfowl considered by King et al. (2009) should also not be discounted.
Following the results of the review, we investigated how the cumulative risk of avian collision within wind farms might be affected by the shortlisted mitigation options, using the Greater Wash as a case study. Seven options were considered – minimal use of lighting and auditory deterrents not being taken forward due to their respective low feasibility and effectiveness. Remote population monitoring is an approach that would be used in conjunction with other options, such as temporary shutdown, to maximise their effectiveness and thus was not considered directly in this chapter.
Mitigation options may operate in a number of different ways, though in the majority of cases by increasing the level of avoidance of wind turbines. As the literature review summarised, relatively little is known as to how effective different measures may be in increasing avoidance and thus it is unlikely to be possible to compare with precision the different short-listed options. Further, there is still a large degree of uncertainty about the level of avoidance of wind turbines that birds demonstrate. The effects of temporary shutdown and changes to turbine design, in contrast, can be more easily quantified. Thus the modelling exercise undertaken here aimed to identify the most promising mitigation measures, along with those that require further work to confirm their value.
The model of Band et al. (2007) was used to quantify the cumulative collision-related mortality of seabirds resulting from offshore wind farms in the vicinity of the Greater Wash, using data collected during Environmental Impact Assessments of the area. In order to demonstrate the efficacy of any mitigation measures, a range of avoidance rates were considered. Population Viability Analysis (PVA) was also used to model the impact of increased mortality on the populations of seven species of seabird – Northern Gannet, Common Tern, Sandwich Tern, Lesser Black-backed Gull, Black-legged Kittiwake, Common Guillemot and Razorbill – which breed in the area.
In terms of overall mortality rates, the greatest cumulative impacts were estimated for Northern Gannet and Lesser Black-backed Gull with an additional 220 and 238 mortalities respectively, assuming a 99% avoidance rate. Results from PVA suggest that, assuming a 99% avoidance rate, populations of Northern Gannet and Common Tern were most likely to be affected by the increased mortality associated with collisions with wind turbines.
The potential effect of the short-listed mitigation options on avian mortality rates was then considered in light of these results. Based on the available evidence from the literature, changes to lighting would be among the most effective of mitigation options, though legislation limits what might be achievable. The use of lasers is most likely to be effective at night, whilst ultra-violet paint is most likely to be effective during the day. The use of decoy towers has shown promise, but would only be effective for certain species, such as seaduck, divers and auks which are themselves less prone to collisions. A temporary shut down of turbines is likely to be highly effective, but financial constraints are likely to highly restrict the length of shut down periods. Targeted shut downs for restricted key periods, perhaps further restricted to times of day when key species are most active, represent a possible option given these constraints and would be worth exploring on a site by species basis. No single measure is likely to be effective at reducing collisions for all species at all times, consequently combinations specifically targeted to the species recorded within each wind farm are likely to prove the most effective mitigation strategy.