Offshore windfarms: the case for migrating birds

Migrating bird species have superlative acquired intellect, since the evolution of the species they have learned to migrate and are not summer tourists. They migrate for two principal reasons – to find food to stay alive and to rear their young in safety with sufficient food supplies thus ensuring the survival of the species.

Go to the profile of Doug Hutchinson
Nov 13, 2017
Upvote 2 Comment

List of Abbreviations

DC                  Direct current

MW                Megawatt

REZ                Renewable Energy Zone

EIA                 Environmental Impact Assessment

SEA                Strategic Environmental Assessment

DECC             Department of Energy and Climate Change

TDC                ‘Top-dead-centre’


Cognisant of the seasons, birds know when to commence their migrations. Inexplicably they are cognisant not only of the earth’s seasons, but also of the earth’s wind patterns, both at their locations and elsewhere on the surface of the globe. They fly when they know thermals and tail-winds will assist their journeys across continents, deserts and over oceans. They somehow find the altitude where tail winds assist flight and remain in those air-streams for as long as possible.

Keeping with the inexplicable, using only this one chance, when they lift-off they know there’s no-turning-back. They fly by day and night … never stopping for any length of time, until they reach their seasonal feeding and breeding grounds. Some species are thought never to stop … they are accorded with the ability to sleep on the wing.

Their supreme intellect is their ability to navigate – they’ve never needed SatNav, apparently using a combination of the Earth’s invisible magnetic field, celestial navigation by the sun, moon and stars together with terrain photographic memories … to arrive to nest beneath the same building rafter (swallows), the same marsh, lagoon, seashore, estuary, sand-hill or hedgerow year after year. Their DNA and innate instincts cannot be undone. 

They don’t fly to air traffic controller’s instructions. To put wind turbines in their flight paths is insanity. Similarly, foraging sea birds can only survive by following fish shoals, placing windfarms in these key feeding areas is compounding insanity.

See Cambridge University Press publication – Environmental Protection, Law and Policy, by Jane Holder and Maria Lee. The authors state that the scientific expert can only offer a partial understanding of environmental problems and hence provide solutions, and this is very possibly the main dilemma currently facing environmental law. [1]

The unwritten rider to this is non-scientific-experts, overseeing the granting of permissions for infrastructure projects, would most probably be even further away from understanding the real issues of bird population survival and thus must take scientific expert advice and use the observation experience of organisations like the Royal Society for the Protection of Birds (RSPB).

From the industrial revolution onwards, as communities grew around coal mines, shipyards, cotton and woollen mills and some of the other early industrial horror installations, the ill effects of industrialisation on both people and the environment emerged.

Within the Cambridge University Press publication – Environmental Protection, Law and Policy, by Jane Holder and Maria Lee [1] – we discover environmental protection became a significant issue for individuals, public interest groups, independent agencies and finally government. The green movement grew on the perceived value of ever-increasing industrialisation and economic growth and the failure to fully consider the human and environmental issues in its implementation. The environmental lobby today is immense, and we know local and state government bodies that ignores it, does so at their cost.

A brief history of onshore and offshore windfarms UK

Wind turbines have been in existence for centuries. [2] Perhaps the most effective development and use occurred in The Netherlands where ‘windmills’ were used to grind grains and pump water; in some ingenuous applications, they performed both functions. Much reclaimed land was drained by Holland’s water pumping windmills and so the prosperity of the country grew and these picturesque installations are now very much revered in Dutch culture. 

The marvellous high technology windmill of today is used for generating electricity and as one would expect, is quite unlike the Dutch icon in purpose, sail or blade design, and physical size.

As the search for sustainable and renewable energy increased, modern wind turbines were initially capable of generating acceptable quantities (kilowatts) of electric power to sustain households or small businesses … and never more so in remote locations.

Britain saw their value and adopted the use of wind turbines. The more meaningful developments occurred from around 1998 onwards, when the British Wind Energy Association (now named RenewableUK) began discussions with the government for the adoption of these machines to form part of the country’s renewable energy electricity supply system.

Government jumped at the proposition since it had significant potential to reduce fuel imports whilst simultaneously reducing total emissions into the atmosphere. Guidelines were published circa 1999, and some 17 ‘development projects’ were granted permission to proceed by April 2001 thus allowing developers to gain technical and environmental experience. [3]

Offshore developments were to be in British territorial waters within a distance of 12 nautical miles (22.2 km) from the coast line and were limited to 10 square miles in acreage with up to 30 wind turbine-generators. This significant action subsequently became known as Round 1 of the UK’s offshore development programme.

Round 2 essentially consisted of lessons learned from Round1 – notably in the sphere of planning permission - and proceeded to advance the offshore industry whilst simultaneously creating an exclusion zone some 8 to 13 km offshore on the grounds of avoiding visual impact and avoiding the shallow feeding grounds of sea birds. [3] By 2003, 15 projects, contributing a further huge 7.2 GW of capacity to the Grid were granted permission to proceed and by May 2010 approvals were obtained for seven Round 1 and 2 sites to be further extended creating an additional 2 GW of offshore wind power capacity. Naturally, each windfarm required new planning applications which included new Environmental Impact Assessments together with full consultation.

Round 3 saw an almighty move into offshore wind energy. This third round of approvals dwarfed by three times the 8.0 GW allocated in Rounds 1 and 2.

A stunning 25 GW of generating capacity was proposed by the UK’s Crown Estates in 9 offshore zones in which individual windfarms would be sited. In January 2010 successful bidders were announced and project construction was commenced. [3]

Power stations – fundamental requirements

For power stations in general, depending on the chosen technology, all power generation plants from conception to implementation are faced with design and commercial trade-offs.

Ideally, all electricity generating plants should be sited close to load centres (to minimize transmission losses) and/or as close as possible to existing grid / distribution networks for convenience of connection, thus avoiding the creation of new electricity substations and overhead line posts or transmission tower runs. Round 1, 2 and some of the more recent developments were naturally located as near as possible to both grid connections and population centres.

Oil refineries would be another example of an industrial undertaking where ideally the installation would be as near as possible to oil product consumers, but it could be seen, oil refineries presented visual impact and dangerous (explosive) and other chemical undesirable qualities and so were thus built well away from population centres. Trade-offs of necessity abound everywhere in all infrastructure projects.

Next on the fundamental requirements list would be foundation geology and access to site. All power generation plants require sound foundations. Nuclear plants for instance are immensely heavy and so the geology beneath them must be surveyed to ensure complete structural safety. Commercial nuclear generating stations also require vast cooling water supplies and so they have always been sited on the coasts of Britain.

Economies of scale very soon enter the infrastructure development equation. When the major 2,000 megawatt (MW) and larger coal fired generating stations (Drax) were being built chiefly in England and Wales, they were sited on or very near to the coal fields Wales, the Midlands, Lancashire, Yorkshire and the Durham and Northumberland coal fields to minimize fuel transportation costs. Mirror image oil and gas fired power plants of London, Hampshire and Wales, irrespective of their installed capacity, were situated near to the oil refineries and gas importing ports on the Thames, Southampton Water and Milford Haven.

Before the major fossil fuelled and nuclear plants were built, consideration was given to public convenience, rail and road routes were studied between manufacturing facilities and construction sites. These studies included road physical and dimensional acceptability; all bridges were studied for their load carrying limits. Massive power plant components were carried on new-concept, multi-wheeled, low-load transport vehicles. Police escorts to construction sites became commonplace. These very slow moving loads were moved during the evening, night and the small hours of the morning in order not to inconvenience the general public. Quite rightly, public perception and acceptance was and still is, vital to industrial development.

Hydro-generating stations needed the largest possible water catchment areas, dam-site geology and land topography considerations were prime fundamental considerations – thus river valleys and river gorges were chosen for hydro-dam sites.

Choosing suitable ideal sites was difficult. Development sites having all the necessary geological, technical and commercial attributes were few and far between and their consideration caused public up-roar and quite rightly so, after all, one wouldn’t want to see the O2 Arena built alongside Stonehenge!

Thus over the years, building everything from garden sheds to power stations or refineries required ‘Planning Permission’ - approvals being granted after private and/or public enquiry and submission review.

Mistakes were made in balancing high scientific content against commercial requirements, however, as economies of scale became the prime requirement, the immensity of electric power projects grew and in almost every instance, the siting of such projects took months and even years to resolve before construction could commence. In certain controversial circumstances, approvals were granted with a recorded list of constraints that were not to be exceeded.

Suffice to say, from early industrialisation, Britain has assimilated a vast experience in planning, siting, building and commercially operating hydro, fossil fuel and relatively latterly, nuclear facilities.

In all cases, the perceived value of economic growth, was and still is, weighed against visual impact, amenity and environmental issues.

Renewable energy spectrum

A couple of decades on from the large output thermal generating stations, global warming and climate change stimulated renewable energy science and the design and development of renewable energy projects. All renewable forms of energy have come under review, wind energy, wave and tidal energy, solar and biomass being the most readily assessed.

The longer term renewable energy form is nuclear fusion. Simplistic explanation points to fusion as being one of the most promising options for generating large amounts of carbon-free energy in the future. Fusion technology is being researched and developed such that gas from a combination of types of hydrogen are heated to extremely high (plasma) temperatures to derive free hydrogen fuel in vast quantities from water (in the longer term seawater). Power stations using fusion technology would have a number of advantages. To name the more notable, no carbon emissions, the process will not add to atmospheric pollution, abundant (vast) fuel supply potential (hydrogen being extracted from seawater) excellent energy efficiency and no long-life radioactive waste. [4]

Fusion power plants would thus lend themselves to baseload generating stations generating very large amounts of synchronous electrical energy at costs that are estimated to be broadly similar to other energy sources. [4] Much of the initial research spade-work has been accomplished in Britain and the world’s largest JET (Joint European Torus) project has produced 16 MW of fusion power. The task ahead now, is to prove the fusion process can work in large scale power plants.

Windfarms – evolution and siting

Clearly countries on or nearest the Equator will benefit primarily, but not solely, from solar power systems – wind turbine-generators will obviously also be used during normal day-to-day operations when wind strengths will allow. Wind strengths in the tropics are variable and even fickle, thus wind turbine-generators contribute very varied electrical outputs in tropical service.

Countries between the Equator and the Poles will benefit from varying combinations of solar, wind and ocean tidal and wave along with biomass energy facilities where favourable conditions exist.

Regions near the Polar Caps will benefit mostly from wind power, although this would seem to be limited to calm-day wind generation conditions. Polar region high to very high wind speeds coupled with severe icing is anticipated to seriously affect wind turbine generator output and usage.

In any given location, wind turbine output varies considerably; in general terms, the output from wind turbines is determined by geographic location, land topography, the season, wind speed, time of day, ambient temperature or more specifically air density, and all these factors contribute to machine final electrical output.

Land geography and topography led to wind turbines being placed in locations having little topographical obstruction. This inevitably meant searching for uninterrupted airflow into the wind turbine, thus locating installations in flat windswept landscapes or on high ground and hill-top locations bringing about further visual impact objections. Land based wind power installations, whilst flexible and easy to locate, has not received unequivocal public acceptance. The combination of visual impact, low frequency noise and very large acreage sites have posed problems for developers over and above all the fundamental power plant requirements.

Research by NASA established wind turbines could generate surprisingly high levels of infrasound and low frequency noise. [5] What is not proven as yet, is what levels of infrasound and low frequency noise are harmful to health. Furthermore at what distance from wind turbines are health concerns not considered harmful. Unclear empirical distance values are currently in use.

Offshore windfarms – project dimensions

Initially, land based and later offshore commercial wind turbine-generators were generally of small output capacity and were within the range 1.3 to 3 MW being the norm. The incessant quest for economies of scale and larger commercial outputs from given site acreages demanded greater turbine-generator capacity development and as a consequence machine sizes have been progressively increased such that the largest in service today would have an output of approximately 8 – 9 MW.  

The American company GE entered the wind power market with a 10 MW turbine generator which has the added advantage of not requiring a gearbox. As with the gas turbine industry, as the development of the industrial gas turbine (also called the combustion turbine) proceeded, gearboxes were eventually designed out industrial gas turbine packages to give a single shaft, rotating at synchronous speed, gas turbine-generator unit.

Wind turbine-generator output is dependent on drive turbine size which in turn means greater air-intake diameters and thus increased blade length. Blade length and blade diameters influence the overall mechanical dimensions and size of all components of the turbine-generator, its nacelle housing and support tower.

Since blade length and thus blade diameter influence the height and dimensions of the tower, the salient realisation being in order to contribute meaningful megawatt capacity to the Grid from a given site acreage, manufacturers and developers must employ larger and larger turbine-generators. These machines would not be acceptable onshore and so are considered only suitable for off-shore applications. Site efficiency therefore increases with a reduced the number of turbines possessing a greater installed capacity.

In order to present windfarm order of magnitude, the project dimensions currently operating off the Kent, Essex, Lincolnshire and Lancashire coasts are shown. [6] The largest class of commercially operating wind turbine-generators in service have capacities of around 8 – 9 MW – the turbine hub height would be some 200 metres (656 feet) above sea level and having blade diameters approximating 160 metres (525 feet). This is not the end of the dimensional story. It has to be realised that whilst the tower and hence turbine nacelle height is approximately 200 metres, when the blades reach their ‘top-dead-centre’ (TDC) rotation position, the total height of the overall structure will be the hub height of the turbine plus the length of the blade, which is half the diameter of the overall rotor. Thus, in reality, the overall installation height would approximate 200 + 80 metres (918 feet).

Table 1 – Order of magnitude – offshore windfarm projects. 

Offshore Project

Distance Offshore

Wind-farm Area

MW Output

Number of Wind Turbines


7 miles (11Km)

13.5 square miles (35 km2)


300 MW


London Array

12.5 miles          (20 Km)

47 square miles (122 km2 )


630 MW


Gunfleet Sands

1 & 2

4.5 miles

(7 km)

6 square miles

(16 km2 )

Phase 1 = 108

Phase 2 = 64

Total = 172


Phase 1 = 30

Phase 2 = 18


5 miles


16 square miles (41 km2 )




Burbo Flats

Liverpool Bay

4 miles

(6.4 km)

3.9 square miles

(10 km2 )



Offshore windfarms are thus enormous to construct, operate and particularly maintain.  Shipping and air transport are now fully cognisant of offshore windfarms. As the technology has expanded, manufacturing has gathered pace such that renewable wind power has proliferated on a rapid and massive scale to out-pace all other renewable energy projects types worldwide.

Table 2 - Indicative wind turbine-generator dimensions - based on capacity. [6] 

Offshore Project



Number of Wind Turbines



Unit MW Capacity

Turbine Height

Rotor Diameter
















London Array










Gunfleet Sands

1 & 2



















Burbo Flats

Original Project


Project Extension







































Fig 1 – Indicative comparison - wind turbine height & blade diameter

Sketch shows indicative machine dimensions as capacity increases. It also gives an indication of the increased risk, particularly when second or third higher capacity wind turbine-generators are added to an existing site. Here again, commercial economies of scale demand the site capacity be maximised by larger capacity wind turbine-generators, however, deeper obstruction flight paths are created.

In summary, the average hub height of a 3.0 to 3.6 MW wind turbine would be expected to be in the region of 134 metres (440 feet) having a turbine blade diameter approximating 110 metres (357 feet) thus giving a hub plus rotor top-dead-centre (TDC) blade total height of 189 metres (620 feet).

By comparison, an 8 to 9 MW wind turbine hub height would be 220 metres in height (722 feet) and having a blade diameter approximating 160 metres (525 feet). Hub plus rotor top-dead-centre total height of 300  metres (984 feet) an author’s sketch is shown in order to indicate approximate physical dimensional comparison of these machines.

Not only are today’s wind turbine generator installations huge, from the technical aspect, the ‘spacing’ or ‘siting’ or ‘arranging’ of wind turbines is a critical factor in windfarm development. Windfarms are arranged in arrays.

Fig 2 – Typical windfarm grid layout

Windfarms were moved offshore for a number of reasons the most critical of which being access to uninterrupted inlet airflow. Ideally laminar airflow is desired having air moving at the same speed and in the same direction, with minimal cross-over of air streams into the wind turbine blades.

Wind turbines arranged in arrays have been found to form a cone shaped, turbulent, slower, downstream airflow to form a ‘wake’ thus, creating turbulence swirls and large eddies that adversely affect the performance of the next-in-line turbine … and so on down the line of turbines; turbulence persists no matter what the direction of the wind.

It has been found were the next-in-line turbine to be positioned too close to this turbulence, the output of the turbine would be significantly reduced and blade vibration damage would result.

Windfarm developers and owners have thus sought to ‘optimise’ the spacing of wind turbines within arrays such that that the next-in-line turbine is spaced a sufficient distance away thereby allowing laminar airflow formation again - for entry into the next turbine. Optimal power output from all turbines within the windfarm array is obtained by this type of positioning design.

Fig 3 – Sketch indicating disturbed & turbulent airflow leaving wind turbine

Beautifully simplified industry favoured distances appear to be 4D to 5D (D = rotor diameter) across or abreast the array line and 6D to 7D in the downwind direction of the array. It should be noted this optimization also takes into account the commercial aspect of cable runs between towers and between towers and offshore sub-stations.  A further realisation would be the further apart the wind turbines, the less installed capacity and ultimately revenue earnings from a given project acreage.

Extensive computer studies have been undertaken to further quantify these various parameters to obtain project development costs. The results indicate the spacing of wind turbines in offshore arrays should be greater. In typical project trade-off circumstances, whilst cable lengths etc., increase, the electrical output of all wind turbines in the array now having more laminar, less turbulent inlet airflow increases generation output to a significant extent. A number of studies, depending on world location and specific details, suggest that a 15 to 30 per cent increase in turbine output can be expected [7] - thereby increasing the revenue stream considerably over the life of the project. Coincidentally, greater wind power output in the national energy-mix reduces emissions to assist national climate change targets.

Growth in wind-turbine installed capacity. [8] – has increasing grown in the last decade.

Fig 4 – UK wind power annual MW capacity increases to year 2008.

Reference - Centrica Lincs offshore project. [8]

Fig 5 – Randomly selected windfarm photo

A randomly selected offshore photograph in good weather and visibility. This is what foraging seabirds and all large and small migrating birds would have to fly through during the day and night to get from A to B.

Let us see how successful you would be, day and night, in autumn fog and bad weather … dodging row upon row of nacelle towers and rotating wind turbine blades revolving in the vertical plane at differing rotational speeds. The photograph was randomly chosen to give an indication of the daunting flight risks to foraging and particularly small and large migrating birds.

If birds are known to fly into static television masts, lighthouses, tall buildings etc., by how much are their risks increased by not only having to avoid static wind turbine towers but also vertically moving wind turbine blades revolving at differing rotational speeds in all weathers of the British Isles and northern Europe?

Onshore, the visual impact and noise perceptions were not just the pique of a few, how planning permission was given to projects like this - ‘on the other side of the road’ - to picturesque villages did nothing for understanding government renewable energy policy or the wind power industry at large. Check former Prime Minister David Cameron’s reaction. [9]

Fig 6 – Windfarm proximity (just the other side of the road) to scenic Lincolnshire village

By contrast, the acceptability of solar voltaic and heating systems is virtually uncontested.

Fig 7 – Typical ‘unobtrusive’ household solar installation.

Offshore wind power is currently the most accessible and adaptable for most of the world’s regions.  That said, it has significant limitations; low wind speeds mean insufficient wind power to turn the blades and the generator output is nil. High wind speeds require the wind turbines to be shut down so that they do not destroy themselves. Wind turbine-generators do not revolve at synchronous speed; several stages of ingenious circuitry converts the generator output into a three phase alternating current having the same frequency to allow connection to the Grid.

Undesirable voltage harmonics and reduced Grid electrical system inertia security are characteristics of this type of power generation; synchronous power generation must be retained to maintain electrical system security.

In general, wind turbine-generators have low capacity factors between 30 to 40 per cent maximum. Government subsidies to initially kick-start wind power design and development got the industry going; subsidies continued in order to stimulate investment and growth of the industry. It could be said subsidies also ‘encouraged’ developers to space wind turbines more closely together, thus increasing capacity per square kilometre or square mile of project allocation.

Now, because of the very considerable variation in wind direction and strength throughout the day, when high or low wind strength prohibits generation, subsidies are still paid. Looked at cynically, in reality, wind power companies are on a winner all the way to the bank – they get paid even when their power plants cannot generate and are shut-down!  Subsidies have meant expensive power, a situation that is more than likely to bring about power purchase agreement changes.

Round 3 windfarms are not only to deliver over three times the capacity of preceding rounds, the windfarms are to be located further offshore as far away as the Dogger Bank some 125 to 290 kilometres (78 to 180 mi) off the east coast of Yorkshire in the North Sea.

The project will consist of four offshore wind farms, each with a capacity of up to 1.2 GW, creating a combined capacity of 4.8 GW.  Planning consent for the first phase of the project (Dogger Bank Creyke Beck) was granted by the UK government in February 2015, and consent for the second phase (Dogger Bank Teesside) was granted in August 2015. Around the world and in Britain development continues unabated, further offshore means windfarm location in deeper water using larger wind turbines.

As recently as the 18th October 2017 Scotland’s 30 MW, Hywind, floating windfarm project was officially declared operational.  Norway’s Statoil and the UAE’s Masdar Company are the owners and will operate the floating Hywind project which is located approximately 25 km from Peterhead in Aberdeenshire on the eastern seaboard of Scotland.

This new approach and new ‘deep sea’ design, together with its manufacturing and unique costruction technology increases the attractiveness and market potential of Hywind thinking. The project has 5 x 6 MW (30 MW) wind turbine generators having a hub heights of 101.0 metres (331 feet) and a rotor diameters of 154 metres (505 feet) making for an overall turbine installation height of 178 metres (584 feet). The windfarm occupies an area of 15 square kilometres or 5.8 square miles. It is now an uncontested fact that offshore windfarms make an enormous contribution to any nation’s power and energy logistics.

Pre-planning and planning

Since both on and offshore windfarms are significant developments they require both national and local government planning permission. The regulations in England, Wales, Scotland and Northern Ireland are numerous, varied, complex, time consuming and very costly, however they are all variations on a theme - technical soundness, electrical infrastructure growth significantly contributing to the national energy mix whilst simultaneously reducing emissions thereby assisting in meeting national climate change targets.

Project investigation, formal application, submission, final assessment and approval processes are also lengthy (2 years at the very least) demanding complex balanced and informed thinking and decision making based on the views and needs of local residents and business, onshore amenities, fishing and users of the sea and air space and last but not least, the impact on the environment and marine and bird life. Note we now find, more than ever, site location and design has everything to do with marine environment and wildlife protection.

Essentially the UK’s Crown Estate is charged with leases and takes care of the environmental assessments of any marine or environmental project in UK territorial waters or the UK Renewable Energy Zone (REZ). [11]

These leases of the sea bed cover areas where off-shore wind power, wave power or tidal power projects together with offshore sub-stations and cable runs are located.  Crown Estates provides strategic support to developers during their project planning and environmental impact assessment processes. Crown Estate works with Scotland, Northern Ireland and Wales in these matters.

Developers need to conduct an Environmental Impact Assessment (EIA) and demonstrate compliance with the Habitats Regulations. A Strategic Environmental Assessment (SEA) is conducted by the UK’s Department of Energy and Climate Change (DECC) or Marine Scotland. Note there have been Government Department name changes and responsibility changes however, whatever the department, the essentials remain the same and are nonetheless considered.

Energy and electric power projects in Scotland require formal applications to build, operate, modify or extend all power stations be they onshore or offshore. Within the marine environment, final project applications come before the Scottish Ministers for consent. Thus, hydro-electric, onshore and offshore windfarms and wave and tidal generating stations all fall into the planning permission requirements category and final submissions are considered by The Scottish Ministers.

As with the rest of the UK, the purpose of the energy consent decision making process is to allow a balance to be obtained between the requirements of suppliers, developers, national energy and planning policy, community interests and environmental considerations. Environmental Statements describing the effects any development is likely to have on the environment must accompany all applications.

The planning authority and public bodies such as Scottish Natural Heritage and the Scottish Environmental Protection Agency as well as other representations made to Ministers are considered during the decision making process.

Numerous important issues have been brought to the attention of Crown Estate and their partner administrative assisting organisations. These concerns cover a wide range of topics such as business and innovations opportunities, cost reductions and funding, seascape and visual effects, bird and fish populations and fishing, electromagnetic radar interference, shipping and aircraft navigation.

An English Planning Inspectorate examines the development submission and makes a recommendation to the Secretary of State for Energy and Climate Change to make the decision on whether to grant or to refuse consent.

It should be noted, in its day, the 175 turbine, 630 MW London Array offshore windfarm situated off the Kent coast was the largest windfarm in Britain, Europe and the world in terms of megawatt capacity. The second phase of the project was not granted consent because of its impact on sea birds.

It should be further noted that The Royal Society for the Protection of Birds (RSPB) in Scotland launched a legal challenge in January 2015 against the approval of four windfarms having some 335 turbine-generators and a combined capacity of 2,284 MW; these windfarms were to be located in the Firth of Forth and the Firth of Tay. In Scotland, final ‘Go – No Go’ decisions are made by The Ministers for Consent.

The legal challenge was on the grounds that the projects posed too great a risk to many thousands of resident foraging and migratory seabirds. Scottish Courts ruled in favour of RSPB in 2016 and ordered the Scottish Ministers to reconsider their decisions and address concerns raised by the RSPB.

By adopting the use of more powerful, newly developed wind turbine-generators one of the developers reduced the number of wind turbine-generators from 125 in the original planning application to 64, thus obtaining for the developer, the same installed capacity and megawatt output with half the number of wind turbines. It is thought very likely other developers of the remaining Forth and Tay windfarms will do likewise. [12]

The hub-heights of larger output turbine-generators are mounted very much higher above sea level and have greater rotor blade diameters potentially posing a greater collision risk threat to large and small migratory birds and foraging seabirds using the same or similar geographic migratory flyways.

The Scottish Ministers lodged an appeal which was subsequently upheld and in 2017 and the original RSPB court decision was overturned. The various Forth and Tay projects were given the green light to proceed with construction.


The wonders of bird migration fascinated avian researchers long before commercial wind power generation captured the headlines. Two fantastic migrations (there and back) take place annually, chiefly in the north and south directions as the seasons change between and intra North and South America and the Canadian Arctic. Bird migrations also occur across Europe extending all the way to South Africa. Then of course there is Central and Eastern Asia, and finally bird migrations cover the seaboards Alaska, Siberia, Japan China, South East Asia and Australia and New Zealand. [13] Thus, bird species are threatened worldwide.

Referring to the premise in the introduction, birds seem to sense and know all about weather predictably, both at their local positions and in other (remote) locations on the globe’s surface. They thus take-off and fly in what are now well researched and defined ‘flyways’ ingeniously using thermals and tail winds to get them across oceans, searing desert locations (Sahara) and over mountain chains like the Himalayas. [13] 

Research shows all migratory birds feed to build up energy reserves prior to migrating. The energy reserves get them across ‘obstacles’ to land and feed again, increasing energy reserves in order to fly on again until they reach their seasonal destinations. [14]

To obtain an immediate general knowledge of the amazing ways in which birds migrate and use mother Earth’s wind-currents one need go no further than to refer to Migration of Birds by Frederick C. Lincoln [16]. This fascinating text reveals the amazing discoveries of observers studying migrating bird flight characteristics. The text was not written with onshore or offshore windfarms in mind, but rather bird (various species) migration in various parts of the world.  The article details aspects of flight behaviour.

The text indicates most small birds favoured a flight altitude between 500 and 1,000 feet. This text also states that many night migrating birds are killed each year by striking lighthouses, television towers or other man-made obstructions and particularly illuminated obstructions; under such conditions, migrating birds seem to be attracted to and are confused by lights.

These observations should be kept in mind because they do have distinct parallels with (>span class="tgc">see RSPB migration routes) [13] as other, notably German research [14].

This poses the question, if birds can be killed by flying into static structures, by how much is their risk increased when one considers wind turbine stationary towers and then blades moving vertically is radial orbit. German research tracking birds with radar also corroborated birds flew at dangerous heights. This German research of birds and their migratory behaviour was conducted in the German Bight which is a key EU windfarm development area today. Indeed, mega-windfarm developments are planned by Denmark, The Netherlands and Germany in this North Sea – German Bight area. [14]

In the UK guidelines are available to developers for onshore and offshore windfarms; Scotland has specifically developed an organisation called the Scottish Windfarm Bird Steering Group (SWBSG - [15] which brings together government, the renewables industry and conservation groups. The steering group provides independent scientific assessment of the impact of windfarms on birds.

SWBSG has undertaken the basic ground work associated with wind power and it has also commissioned a series of specific studies covering, natural heritage zone bird population estimates, reviews of the cumulative impact assessments in the windfarm industry, modelling cumulative impacts of windfarms on birds, the precision and bias of bird fatality using contrasting carcass detection strategies as well as desk-based reviews of the methods used to assess the effects of windfarms on different bird species. Carcass counts for onshore windfarms were obviously easier to study, however it is anticipated carcass counts of offshore particularly during the winter period will be infinitely more difficult to ascertain.

German research (wonderful attention to detail) [14] emphasises not only the wonders of migration, but shows how, by tracking bird migrations with radar, significant insights were discovered about numerous migration species.

These radar studies revealed insights into migrating flight characteristics, flock numbers, altitude, speed, distances covered and bird energy expenditure. Based on this research (congratulations offered!), firm recommendations about the siting of offshore windfarms followed.

Researchers found they were able to investigate diurnal collisions only in good weather conditions, which naturally were expected to be few in number when considering large species such as geese and ducks, however researchers were not able to investigate small bird species, which according to findings, were more frequently involved in collisions.

The far seeing recommendations also were cognisant of the fact that, significant migration was nocturnal and terrestrial birds in particular, were attracted to illuminated offshore obstacles increasing the potential for collision death and casualties.

Remarkably, researchers were able to demonstrate and document by using thermal imaging that disorientated birds flew around platforms repeatedly, so that both their risk of collision and their energy expenditure increased, putting their very existence at risk.

RSPB research corroborates German experience and points to another ecology horror story; birds were disastrously attracted and drawn into the flames of offshore oil and gas platform gas flares!

Significant German recommendations were the avoidance or abandonment of windfarms in zones with dense migration and in foraging grounds.

Wind turbines should be arranged in rows parallel to the main migratory flight directions and free migration corridors of several kilometres width should be allocated between windfarms.

Significant windfarm operational observations indicated wind turbines should be shut down during nights predicted to have adverse weather during high migration intensity. After all, ‘there and back’ migration only takes place twice a year at reasonably predicable six monthly intervals.

Further recommendations very sensibly state that windfarms not be sited in known large or small bird migration flyways or fly-zones.

Whilst accepting birds have the ability to avoid ‘obstacles’ – presumably static obstacles having no huge diameter – placing windfarms occupying tens-of-square-miles in flyways meant, in order to fly around these obstacles, increased bird flight energy expenditure, thus exhausted, migrators potentially never reach their destinations.

What can be learned?

German research hits the nail squarely on the head. Windfarms must not be sited in known migration flyways. Who would disagree? Britain and north western Europe are notoriously windy areas, and common sense tells us, subject to design and commercial fine-tuning trade-offs (visual impact, noise etc., would be a prime examples), the siting of windfarms can be almost anywhere!

Onshore or offshore windfarms should therefore not be located anywhere near migration flyways.

Design plays a crucial role in the avoidance of bird collisions; particularly since it has been discovered through much computer research that current industry standards and preference distances between wind turbines is now considered to be too close. Clearly the further apart the turbines, the greater the opportunity for a bird to pass through unharmed; this situation also suits the developer/owners of windfarms because less turbulent airflows into turbines increases generator outputs and decreases potential blade wear-and-tear damage making enormous savings and increased revenues  over the life of the project.

Wind turbine arrays should logically be designed in rows parallel to the main migratory flight directions and free migration corridors of several kilometres width should be allocated between windfarms.

The further development of windfarms with larger output wind turbine-generators deepens the collision heights through which birds have to pass. Over the life of the windfarm the potential bird deaths and causality statistics do appear to be more deadly.

Now that these significant renewable projects have been established – and Britain being one of the largest developers, it should be mandatory that radar, thermal imaging, GPS and photography technologies be developed and used be for the on-going life of all windfarms to ascertain the effects on bird-life. 

The Royal Society for the Protection of Birds (RSPB) is without doubt the independent authority on British birds. As such they should be consulted in every instance, their knowledge base and experience is invaluable to the country. They should have the final consultancy word when it comes to environmental sanction of windfarm development. RSPB, instead of desk-top consultants, should write the environmental (bird) guidelines for onshore and offshore windfarm project development in future.

Whilst Scotland for example has created separate organisations (SWBSG) to study collision details, carcass counts and the anticipated distance of carcass catchment areas from wind turbines etc., no such details come close to indicating the potential carnage that may be taking place at sea. Thus, emulating German enviro-research, the use of radar, thermal imaging etc., should now be the focus to prove beyond all doubt, that installations do not harm birds … and if so, in what annual statistical proportions is harm inflicted on birds in general … or what harm is inflicted on specific species of birds.

Everyone agrees today’s huge windfarm structures present danger to helicopters and light aircraft. Britain’s CAA has detailed lighting requirements they consider necessary for windfarms. What we do not know is how cognisant were they in considering singular bird or migration behaviour particularly in bad weather.

It seems more research is needed on the matter of lights (flickering or otherwise) on birds since several independent studies, conducted by various countries, corroborate bird confusion with illuminated structures.

Whilst design is a crucial issue, windfarm operation is equally crucial; German research indicates stopping windfarm operations for short periods at night (light-confusion) and in bad weather, during heavy migration periods. This would be most advantageous to all migrating species.

This operational activity would not be financially ruinous to already heavily subsidised – and/or generously power purchase priced, offshore windfarm power companies. One feels it’s the least they could do!  

The nation’s weather bureau and National Grid advised by RSPB (who would be well aware in advance of bird migration gatherings) would order these key shut down periods. In doing so, National Grid would also be able to plan well in advance, the replacement power generation needed for such loss of windfarm capacity for these short intervals which would occur twice (migration there and back) a year.

Project design plays the most important role in protecting birds. Combining both design and operational strategies as suggested by German research should be made mandatory.  Activities like this would earn the RSPB Charity some well-earned revenue and help going cap-in-hand to the general public and sympathetic organisations and industry for donations.

The siting of windfarms both on land and in coastal areas has presented considerable concerns, and in some cases public outrage, because of bird collision deaths. Whilst this paper is chiefly concerned with Britain, the growth of windfarms in America, China and Europe for example, has been phenomenal. We hear nothing of China, but in America public concern and outcry has been well publicised.

The Hywind deep water ‘floating’ windfarm off the Scottish coast takes offshore technology several rungs further up the offshore development ladder, making the ‘spread’ of windfarm projects to almost ‘unlimited size’ possible.  The need to conserve and accommodate avian needs has never been greater.

The addition of windfarm extensions, with larger capacity wind turbine-generators, deepens the hazard heights and thereby substantially increases collision risk. These project additions should be now be prohibited in all areas known to be near migration flyways.


  1. Cambridge University Press publication – Environmental Protection, Law and Policy, by Jane Holder and Maria Lee.
  2. Wind Energy Foundation –
  4. Fusion Energy –
  5. NASA Research –;
  7. World Renewable Energy Congress 2001 – Sweden 8-13 May 2011;
  8. Lincolnshire – Centrica Lincs off-shore wind project;
  11. Crown Estate; Government & Crown Estates –;
  16. 16. Lincoln, Frederick, C. and Steven R. Peterson.  1979.  Migration of birds. Circular 16, U.S. Department of the Interior, U.S. Fish and Wildlife Service, Washington, D.C.  Northern Prairie Wildlife Research Center Home Page. Accessed online
Go to the profile of Doug Hutchinson

Doug Hutchinson

Director, Power Generation Services Pty Ltd

Career achievement, - working as Power Company Operations Manager on the US$ 540 million, 700 MW, joint venture, Shajiao 'B' power generation project in Guangdong Province PRC, the World Bank / IFC came to study the project and Doug was later asked to write and present a paper to The World Bank / USAID organisations for their " Private Sector Power in Asia" conference held in Kuala Lumpur, Malaysia, on 27 - 29 October 1992 covering the private power experience in China. Author – Central Electricity Generating Board – A Method Study Approach to Power Station Operation. Author - IET Eng/Ref - Overview, Asset Management, Gas Turbine Power Stations. STEM Ambassador – UK

No comments yet.