Offshore wind developments - collision and displacement in petrels and shearwaters: literature review

Annex 1: Workshop Report

Workshop 1: 1300 – 1600 UTC, 10^th March 2022

Workshop 1 brought together ecological experts on the three key procellariiform species (Manx Shearwater, European Storm-petrel and Leach's Storm-petrel), as well as experts on seabird vision and the impacts of artificial light on seabirds. A draft version of the literature was circulated to attendees in advance of the workshop and a summary of the draft review was presented at the start of the workshop, along with the knowledge gaps it had identified, the priorities amongst those, and brief suggestions for filling them.

Participants

• 43 participants attended the workshop and engaged well with the information presented and questions posed. The following 27 organisations were represented:- Acadia University, Canada
• Azores University
• Bangor University
• BirdLife Greece
• Birmingham University
• BTO
• Cardiff University
• CORY'S (Spanish environmental consultant)
• Environment and Climate Change Canada
• Faroese Environment Agency
• JNCC
• LBHI (Agricultural University of Iceland)
• MacArthur Green
• Marine Scotland Science
• Memorial University of Newfoundland
• NatureScot
• RSPB
• Scottish Association for Marine Science
• South Iceland Nature Research Centre
• UKCEH
• University of the Azores
• Universidad Autónoma de Madrid
• University College Cork
• University of Gdansk
• University of Oxford
• Vilnius University

Discussion summary

Each participant was randomly allocated to one of three breakout rooms. Each breakout room included two members of the project team, one acting as a facilitator and one as a scribe. A Jamboard (online whiteboard) was set up for each breakout room in advance and a link provided for participants so that they could add ideas or comments during the session or at any time during the week following the workshop. The scribes aimed to ensure all comments were captured on the Jamboard, adding any points not written by the participants themselves.

Participants in each of the three breakout rooms discussed five key questions, during two sessions.

Session 1:

1. Have we missed anything important from the review?

2. Have we identified the knowledge gaps correctly?

3. What are the priority knowledge gaps in terms of wind farm risk assessments?

4. What risks/potential mitigation should we focus on (in the next workshop)?

Session 2:

5. Recommendations/challenges (technological, logistical, temporal, ethical, financial) for addressing knowledge gaps

Following each session, all participants returned to the main room and each of the breakout room facilitators provided a summary of the key points discussed within their group. It was generally agreed that the literature review was largely complete and that the knowledge gaps were correctly identified, but some suggestions for minor edits or additions were made. Each of the three breakout rooms came to similar conclusions regarding the priority knowledge gaps and there were lots of suggestions for addressing knowledge gaps, although it was acknowledged that many would be challenging to fill. A summary of the points raised, and the actions RSPB have taken as result, follows.

1. Have we missed anything important from the review?

Comment	RSPB Response	Notes
Did the review cover demographic consequences of displacement/collision etc? Possibly through individual based models?	No change	The review covers demographic parameters but implementing models is beyond the scope of this work.
Importance of considering dual foraging (where breeding birds alternate between long and short foraging trips) in these species.	Implemented	The review already mentions evidence for dual foraging in the Manx Shearwater and European Storm-petrel 'Foraging ecology' sections but we have now highlighted that it should be considered when using foraging range data for risk assessments.
Think about specific questions around light attraction to target future work, e.g. distance of attraction to lights - how large is the light "catch basin"?	Implemented	The review already mentions the range over which light attraction occurs as a knowledge gap, but we have added explicit mention of the 'light catch basin'.
Light attraction is important but note that there are two distinct processes: disorientation of adult petrels in foggy conditions, and response of fledglings which are orientated to move towards light to reach the sea.	No change	Already included
Important to consider lights at ports, harbours and other infrastructure developments associated with ScotWind as well as the actual wind farms and associated vessels.	No change	Already included
There is evidence in Canada of attraction to oil and gas platforms.	No change	Already included
Construction phase may be more important than operational phase as more lights/disruption.	Implemented	Added a sentence to point this out in relation to displacement and barrier effects and added 'construction activities' as part of light attraction considerations.
Many more collisions with buildings when lit (see Guilford et al. Bird Study paper).	No change	Already included
We need more information on the impact pathways; is light attraction/disorientation a separate pathway or are they part of impacts such as displacement, e.g. attraction displaces birds from where they would be otherwise. How do we incorporate that into impact assessments?	Implemented	Noted in lighting attraction introduction that light attraction may lead to displacement and added: "We do not consider light attraction to be a separate impact pathway, but it may exacerbate one or more of the recognised impact pathways (e.g. collision, displacement)."
Fledgling behaviour likely most important but has been the focus of other studies.	No change	Already included
Fledgling flight heights.	Implemented	Added to knowledge gaps: "There is a need to consider flight heights when arriving at or departing/fledging from high elevation nesting sites, as well as when birds are away from the coast."
Understanding of the first few days after fledging, when birds don't have good control of flight and are vulnerable to weather etc. Need to differentiate from light attraction.	Implemented	Added to knowledge gaps: "Fledglings may have particularly poor flight control in the first few days after fledging, making them more vulnerable, but our knowledge of fledgling behaviour is poor."
The review is bird-focused, what about structural elements of windfarm infrastructure.	No change	Beyond the scope of the review, although some discussion around mitigation options.
Maps in review don't show the Irish colonies. There will be connectivity with Scottish colonies, and non-Scottish colony birds might be using Scottish waters (e.g. Faroes).	Refer to MS	No change to maps requested, but note added to figure legends to highlight the need to consider colonies from outside of Scotland.
For apportioning, is it only the closest SPAs that are important, or all within foraging range? Is there colony segregation of foraging areas? e.g. Manx Shearwaters have a mixture of these effects depending on behaviour; on longer trips they aren't segregated to colony but they are on shorter trips.	No change	Foraging area overlap is discussed in the review. The details of the apportioning method (e.g. which colonies are included) are not part of the review.
Habitat preferences of prey/prey distributions (maybe limited data). How might prey distributions change in wind farm footprint and influence attraction?	Implemented	Added to knowledge gap around diet. Is already mentioned as a possible cause of attraction.

2. Have we identified the knowledge gaps correctly?

Comment	RSPB Response	Notes
Basic morphometric data
Physiological/morphological differences between Welsh and Scottish birds are unlikely.	Implemented	Added to knowledge gap that differences are not expected to be large.
Flight data
Need to understand how birds gain altitude when getting to burrows high up in colonies, e.g. Manx Shearwaters on Rum	Implemented	Added to knowledge gaps: "There is a need to consider flight heights when arriving at or departing/fledging from high elevation nesting sites, as well as when birds are away from the coast."
Current flight height assessment is unreliable, probably underestimates altitude. It is difficult/computationally complex to interpret altitude from biologging data.	No change	Limitations of current data are already discussed.
Flight heights in different weather conditions and day/night. If we can rule out that they fly at collision height under any circumstances, collision rate will be virtually zero.	Implemented	Added to flight heights knowledge gap.
Flight height/behaviour with wind speed/weather.	Implemented	Added to flight heights knowledge gap.
At-sea distributions/overlap with leased areas
Likely to be site specific causes in variation	No change
Diet
Link between prey and habitat	No change	Already included.
Molecular techniques are an important method to carry out diet analysis	No change	Included in suggestions for filling knowledge gaps.
Some molecular analysis of diet is being carried out for Welsh colonies.	Implemented	Have noted in evidence needs section.
Behaviour (avoidance/attraction)
Attraction/disturbance by boats	Implemented	Added to avoidance/attraction knowledge gap.
Light attraction/disorientation
Distance over which light attraction may occur.	No change	Already included
Conceptual understanding whether it is attraction or disorientation that makes birds appear round lights.	No change	Already included
Multiple lights on multiple wind farms could appear more like a starscape and cause more problems than a single light.	No change
Other
Diurnal activity patterns.	Implemented	Added to knowledge gaps (especially for Leach's Storm-petrel)
Construction vs operational phase impacts.	No change	The same knowledge gaps apply to both phases. 'Associated activities' are included in current attraction/avoidance knowledge gap.
Break down broad light attraction category.	No change	This is already broken down in the knowledge gaps section.
Detection, particularly at the start of the assessment, plus biases in detection, both with DAS (not detecting ESP) and boat based (including potential attraction of birds to survey vessels).	No change	We have commented on the problems with aerial and vessel-based surveys.

3. What are the priority knowledge gaps in terms of wind farm risk assessment?

Comment	RSPB Response	Notes
Effects of light influencing collision, displacement and barrier effects.	No change	Already included
Need to understand whether flight height changes in response to turbines.	Implemented	Added to flight heights knowledge gap.
Potential attraction to vessel lighting.	No change	Light attraction already widely covered.
Is there more published on birds attracted to fishing vessels?	No change	Attraction to vessels (including fishing vessels) is already discussed, but a full review of attraction to fishing vessels is beyond the scope of this piece of work.
Fledgling risks on first migration (at night especially). How long are juveniles vulnerable to light pollution and is this linked to visual physiology?	No change	Already included
There may be other drivers of attraction to infrastructure, such as sound.	Implemented	Possibility of attraction to sound is mentioned in the review, but have added to knowledge gap around attraction/avoidance.
Indirect pathways associated with effects of light on prey.	No change	Possibility of lights increasing prey availability is mentioned. Knowledge gaps include changes in prey distributions around wind farms.
Any novel pathways?	No change	Everything additional identified during workshops has been added.
How do the limits of our knowledge affect our ability to carry out assessments?	No change
Collision rate	No change	Lack of empirical data regarding impact assessments is already discussed.
The birds' ability to detect rotating blades. Could inform mitigation measures to increase detectability of the pylon and blades under different light levels and visibility.	Implemented	Added to avoidance/attraction knowledge gap.

4. What risks/potential mitigation should we focus on in the next workshop?

It was noted that any mitigation must apply to a broad suite of marine birds, and not just petrels and shearwaters.

Light attraction

• How restrictive are permissible lighting patterns/wavelengths?
• Experimental design to understand changing light features (with a dark control).
• Consider key periods of the year when lighting is an issue, e.g. fledging period.
• Absence of light is potentially worse if birds cannot see the turbines. We need to better understand birds' response to light at sea.
• There is some evidence of storm-petrels foraging at night at illuminated fish farms. It would be good to understand the mechanisms.
• Training of vessel crew in handling and releasing birds attracted and grounded on vessels, according to an established protocol (noting that there are existing examples for oil and gas platforms in Nova Scotia).

Other

• Changing the height of turbines.
• Methods to increase the detectability of pylons/blades under different visibility and light levels. Make them detectable at a sufficient distance for birds to change flight path and avoid them.
• Preventing predators from nesting/spending time around turbines.
• Is it possible that an underwater array might provide shelter for fish and so attract birds that way? Can this be mitigated for?
• A better understanding of attraction to noise, e.g. diesel generators on St Kilda.

5. Recommendations/challenges (technological, logistical, temporal, ethical, financial) for addressing knowledge gaps.

The importance of identifying the easiest gaps to fill was highlighted, as well as the need to consider which aspects should be addressed by academia and which by the offshore wind industry.

Basic morphometric data

Focus on easier work (e.g. morphometric data) first, then look at more complex studies.

Scottish morphometric data won't be much different from Wales and can be done in a couple of days, e.g. by an established ringer.

Flight data

Radar:Flight height can be measured with radar but has biases. Species ID (e.g. Manx vs Balearic Shearwater) is difficult with radar but perhaps mobile radar units could be deployed in places like Rum with only one species of shearwater. However, there is a trade-off between radar size and accuracy.. Could the equipment be placed on buoys to measure flight heights at sea?

Thermal imaging cameras could be used to detect storm-petrels at sea and record behaviour. Could flight heights be worked out from these images? It may not be possible to identify to species level (e.g. Manx vs. Balearic Shearwater), but that may not be important.

Hi-Def have been doing interesting work on flight heights from aerial images, but confidence intervals may be large. A report on this work is forthcoming: Humphries G, Fail T, Watson M, Bickley D, Peters-Grundy R, Scott M, Keogan K, and Webb A (in review). Aerial photogrammetry of seabirds from digital aerial video images using relative change in size to estimate flight height. Marine Biology.

Data from cameras attached to birds has been used to estimate the height of birds based on the tilt of the horizon, but this is challenging.

GPS and altimeters have been used to measure flight heights of Manx Shearwaters, but both have large errors.

Behaviour/flight height may be different to normal within a wind farm, as in gannets, so work within wind farms is important.

When does behaviour change from shearing to gaining altitude and vice versa?

Tracking:

Tags providing high resolution data are available for Manx Shearwaters.

Long term tag attachment is possible on storm-petrels with sutures, but that method would be challenging to license in the UK. Short-term tagging during the breeding season is adequate for adults/immatures prospecting but not for fledglings.

PathTrack tags record instantaneous speeds. These are not currently automatically available with data download but can be requested.

Accelerometers are now/soon to be available for storm-petrels, but still won't give flight heights.

Is there an alternative to altimeters? The accuracy of altitude data from high resolution GPS data has been tested but still had large errors. High resolution data for storm-petrels is not yet possible due to the small battery sizes needed to keep tags small enough.

MOTUS could have potential for measuring height as well as location, but it is difficult to establish an array of receivers offshore. Receivers have been installed on oil and gas platforms and supply vessels in Canada, and it may be possible to deploy them on buoys at development sites. Any such inclusion of receivers in infrastructure would need to be considered at the planning stage for offshore wind farms. . GPS might be better, but remote-download tags are not yet small enough for storm-petrels so they need to be recaptured.

At-sea distributions/overlap with leased areas

This information becomes more important to understand if it is used in deciding where wind farms go.

There are huge impacts of Leach's Storm-petrel predation by Great Skuas at St Kilda. There is some genetic evidence that some of the birds eaten may be from Canada. This is an example of the need to understand connectivity between Canada and Scotland, and not just focus on birds from Scottish colonies.

Safe access to many colonies is a logistical constraint for tracking and determining at-sea distributions.

Radar can be used to look at density at sea before/after construction, and in combination with other studies such as tracking could help us to understand juvenile/adult ratios.

MOTUS: Tags are currently too big for storm-petrels but could be used on Manx Shearwaters. Useful for non-breeders/fledglings as long-term deployment outside the breeding season is possible. Detection distance is limited to line of sight. There is currently no UK network, but there is one in Canada which would be useful to learn from. It is important to incorporate at the planning stage if putting receivers on offshore structures. Unclear whether MOTUS could provide data on flight height and avoidance as well as distributions.

Detection: Carry out targeted digital aerial surveys (DAS) with experimental approach to detectability, for example using decoy models of birds to assess detectability under different conditions.

Rescue programmes, such as that for grounded Manx Shearwaters in Mallaig, could be used in association with ringing to identify source colonies. Birds could be tracked from wind farm areas or if stranded on vessels or structures, but remote download of data would be required.

Dye marking of large numbers of birds at colonies could be used to look at whether adults or young birds interact with wind farms.

Birds could be caught at sea and stable isotope or genetic analysis used to identify their origin, although catching at sea is challenging and may not be possible.

Diet

Change in community of marine life in wind farms is likely. It is important to understand birds' diet to understand how these changes affect the birds.

University of Oxford is currently carrying out diet studies, including metabarcoding. Cardiff University has performed metabarcoding of diet samples for many species, including storm-petrels. There needs to be a larger study using DNA metabarcoding, but it would be easy to collect samples.

Visual diet analysis is valuable and much cheaper than molecular. Molecular diet work is likely to be better than traditional visual analysis as it is very hard to identify prey to species level when samples are tiny/degraded (especially faecal samples), and visual identification is biased towards less digestible items such as squid beaks. Any diet studies are much cheaper than tracking.

Could faecal/regurgitate samples be collected by ringers? Would need to consider the logistics of transporting samples to the lab, but this is not too challenging.

It would be useful to link diet data to tracking information from the same individuals.

Is diet or productivity/prey distribution more important? Some knowledge of diet is required before being able to infer predator distributions from productivity/prey distributions.

Behaviour (avoidance/attraction)

Fledglings could be tracked, but it would be necessary to recapture them if remote download is not possible. Track adults and juveniles from the same colony to see if interactions with wind farms are different for different age classes.

VHF: receivers have been placed on oil and gas structures, but it is difficult to get a good sample size.

Radar could be used to quantify flight lines. Changes in flight lines are evidence for attraction/avoidance. The detection distance of portable radar is 72 nautical miles. Memorial University (Newfoundland) has a mobile radar system that will deployed at Leach's Storm-petrel colonies to study their behaviour around artificial light.

Look at circumstances of behaviour in the vicinity of existing lights.

Combine multiple methods (tracking, radar, camera etc). how do we get control site/set of birds, does this need to be tracking?

Light attraction/disorientation

An experimental approach is important, despite the challenges. Look at light range, wavelength, pattern and adults vs immatures.

Behaviour at the colony might be different from at-sea behaviour. Could you conduct experiments at sea using vessels or structures? Experiments will need to use lights that are possible to use on turbines/vessels and these should be standardised across studies using different locations/species.

Is response to light related to colony proximity? This would need both at-sea and landfall groups.

Studies at SPAs would require Habitat Regulations Assessment. Experimental studies might injure the birds and would be harder to licence than studies that take advantage of existing/proposed differences between developments/locations. Perhaps some sort of cushioning could be used on boats/structures to protect birds from impact during experiments.

Focus research on current windfarms in the Irish Sea (e.g. Robin Rigg) as there are Manx Shearwaters in the area. Can lighting on existing turbines be changed to monitor changes in behaviour using GPS tracking?

Could expertise within the offshore wind farm sector be harnessed to construct bespoke experimental structures at appropriate locations?

Bardsey lighthouse changed to a red flashing light in 2014 and there have been virtually no collisions since. There were a lot of reviews in the 19th century of birds flying into lighthouses, this should be reviewed as a starting point.

A questionnaire could be sent to vessel operators about birds found on deck. Onboard fisheries observer programmes could be used to gather data but are limited in the UK and only take place during the day. There is currently a project in South Georgia and previously one in New Zealand using these methods. Cruises around the UK with naturalists onboard (e.g. National Geographic) could be used for better species ID. JNCC also runs seabirds at sea surveys. We might be able to ask wind farm maintenance vessels/crews to partake, or it could be made a requirement in certain areas/settings.

Look at existing studies for the proportion of adults killed when attracted. It would be difficult to monitor the number of collisions at offshore structures.

Bio-acoustic studies could be used to pick up calls around structures/vessels/colonies. Caution is needed in interpreting the data because of changes in vocalisations in response to stress.

Systematic, rather than opportunistic, surveys of oil and gas platforms would help to understand the drivers of light attraction and would allow a finer scale temporal analysis.

Radar/cameras (BACI studies) could answer some of these questions.

Understanding the impact of different weather conditions is very important.

Light attraction is the biggest unknown but may not be the biggest issue. We don't know enough about collision/displacement either.

Workshop 2: 1530 – 1700 UTC+1, 31^st March 2022

Workshop 2 focused on mitigation, particularly in relation to the potential impacts on procellariiform seabirds of the artificial lighting associated with offshore wind developments. The workshop began with a presentation on the key impact pathways identified in the review and Workshop 1, and some suggestions of mitigation options. A second presentation from Anatec described the current lighting requirements of offshore wind farms and associated infrastructure and activities.

Participants

• 39 participants attended Workshop 2, from the following 26 organisations:- Anatec
• APEM Ltd
• BirdLife Malta
• Cardiff University
• Civil Aviation Authority
• EDF Renewables
• Environment and Climate Change Canada
• HiDef Surveying
• Houston Audubon Society
• JNCC
• Marine Scotland Science
• Maritime and Coastguard Agency
• Natural England
• NatureScot
• Northern Lighthouse Board
• ORE Catapult
• ØRSTED
• RSPB
• Scottish Power
• South Iceland Nature Research Centre
• SSE
• UKCEH
• University of Birmingham
• University of Gdansk
• University of Oxford
• Vattenfall

Discussion summary

Discussion was structured around three broad topics: changing the nature of lighting, changing lighting infrastructure, and other mitigation options. It was generally agreed that changing the nature of lighting (e.g. reducing lighting or changing the wavelength, intensity or pattern of illumination) would not be possible as lighting of vessels and structures is highly standardised and aims to maximise safety of vessels and aircraft. Shutting down turbines at key times was also considered not to be feasible, but other options were discussed, as follows.

1. Changing the nature of lighting

No lighting (or turning off lighting at key times, e.g. fledging period)

Not an option from a safety perspective. Shouldn't be considered as mitigation because of serious concern about turbines not being lit for even a short period of time.

Aviation lights only come on at night.

Reduce intensity

There is provision within aviation lighting rules to reduce lights when visibility is above 5 km. Lights can be dimmed up to 90% during reasonable weather.

There is not enough evidence on the impact this would have on different seabird species.

Intensity is more important than colour in bird night vision. The impact of different intensities also depends on atmospheric conditions (fog, rain, etc.). Any conditions that create large diffuse pools of light is the problem.

Bird vision is usually fully functional after a few days. However, there are suggestions that for burrow-nesting seabirds this may not be the case.

Juvenile burrow-nesting seabirds develop their eyes fully after they fledge:

• - Mitkus, M., Nevitt, G. A., & Kelber, A. (2018). Development of the visual system in a burrow-nesting seabird: Leach's storm petrel. Brain, Behavior and Evolution, 91(1), 4-16.
• - Atchoi, E., Mitkus, M., & Rodríguez, A. (2020). Is seabird light‐induced mortality explained by the visual system development? Conservation Science and Practice, 2(6), e195.

Reduce number of turbines illuminated

If the number of turbines lit is reduced, the intensity of lighting would have to increase to compensate so this isn't always viable.

Lighting of non-turbine infrastructure could also pull birds off course (especially fledglings). Reduce, turn off, or cover other lights associated with turbines (e.g. maintenance vessels). Decrease the activity of maintenance vessels, or other lighting that isn't crucial, during high risk periods for birds (e.g. fledging).

Alter pattern of illumination

There needs to be consistency across wind farms to avoid confusion to mariners (especially recreational) and to comply with international standards. Marine navigation lights (UK) generally have a character of 1 flash every 5 seconds (Significant Peripheral Structures) or 2.5 seconds (Intermediate Peripheral Structures).

Alter colour of lights

Again, there needs to be consistency across wind farms and compliance with international standards so this is unlikely to be possible.

Search and rescue (SAR) lights are red to avoid affecting the night vision of crew. No other colour is possible. White lights are used in some circumstances for obstacle lighting for aviation but this has the potential to disrupt night vision of crews.

Is there a way of changing the wavelengths of the lights (e.g. reduce blue wavelengths) to alter the birds' perception of the lights without changing the colour as perceived by humans (so as still to comply with maritime standards)?

Additional lighting

Is more lighting possible, as less is not? Could additional high attraction lighting on buoys be used to navigate birds around high risk areas, perhaps temporarily during the fledging period?

2. Changing lighting infrastructure

Shielding/directionality of lights

The peak of an aviation light beam is between 3-4 degrees above the horizontal plane and less than 10% is 1-1.5 degrees below the horizontal plane, so only 10% is directed down.

Vertical divergence of marine lighting is only a couple of degrees off of the horizontal, but the light needs to remain visible to all sizes of vessels, either up close to the turbine, or at the extreme range of the light.

Could you light up the wind farm at night from a light placed on another structure, pointing at the turbine? To avoid attraction and collision with the light itself, place it below the sea surface. This is unlikely to be feasible as turbine lighting is standardised to maximise efficacy and safety.

Lighting on ships could be directed towards the deck to reduce scatter.

There is probably potential to have design discussions with turbine designers as to how access door lighting could be altered, as well as with vessel suppliers. As such, there might be some mitigation solutions which could be explored with relative ease, or are already being implemented as standard, to minimise attraction for Procellariiformes.

Radar-activated lighting

There are already systems in some parts of the world where lights only come on when an aircraft is detected, but this is not in UK EEZ regulations at the moment. There are different technologies that can enable this. Could this be possible for vessels on the sea too?

A detection system isn't possible for all marine vessels, especially ill-equipped recreational vessels. The ability to detect and track small yachts/vessels, particularly in poor weather is difficult and would not be reliable. As such, the provision of lighting must always be for the lowest level user.

It is crucial to keep the importance of lighting in perspective and cater for all situations and everything that might be flying, e.g. civil aviation and search and rescue could be present at any time.

Lighting is required to provide ships with sufficient warning to take avoiding action so needs to consider all types of vessels, including very slow turning vessels.

3. Other suggestions

Increase blade height

This has benefits outside of mitigation for birds. 22 m of clearance is the required minimum to reduce impact on marine vessels.

Increased hub height would require feasibility assessment on a case-by-case basis of manufacturing and installation of foundations tower sections.

The threshold for crossover from fixed bottom vs floating turbines is likely to increase over time (perhaps up to 100 m). There's a relationship between increasing turbine size and jack-up/crane lifting capabilities and the latter may be a limitation for increasing blade height

As turbines become larger, we will likely see a slight increase in the sea level to lower tip clearance. We will also see a larger rotor diameter but not necessarily a large increase in the overall rotor-swept area (i.e. typically fewer/larger WTGs meaning the overall swept area of the rotor in the 'danger zone' for birds could be proportionally reduced.

Shut down turbines at critical times

The UK will be reliant on offshore wind in the future so switching off turbines would be the worst-case scenario.

Increase detectability by marking blades

Review recently conducted for Natural England. It is likely that something can be done to make blades more visible to birds flying through, and therefore prevent collisions.

Collision with towers is also possible. Maximising contrast between towers and blades (e.g. black/white stripes on blades and towers) has been looked at. There is currently a project in Norway looking at this.

However, the need for consistency across wind farms must be considered, to avoid causing confusion.

Use of sound to deter seabirds or avian predators

Operational offshore wind turbines have relatively high noise emissions (~110+ decibels). This could be a consideration if these species actively avoid noise sources. There is some evidence that Manx Shearwaters are attracted to generators on St Kilda by sound.

There is an Irish project testing if sound could be used to deter birds. Sound signals (e.g. foghorns) on turbines at periphery of windfarms which sound during poor visibility (under 2 nautical miles). There are characteristics that must be met (1 long blast, 2 short blasts every 30 seconds).

It would be interesting to test whether birds respond to foghorns or if there are sounds beyond human hearing range that might be detected and deter birds during times when risk is high. Although obviously has implications for displacement.

Train vessel crew in safe handling/release of stranded birds

SOPs for stranded birds.

Posters have been created for vessels anchored in St Brides Bay, Pembrokeshire, explaining what to do if Manx Shearwaters land on boats at night. This method has been repurposed for different species and locations around the world.