Migrating raptors are attracted to turbines as potential landing spots 

Wind turbines at sea are a danger to birds of prey particularly during bad weather, a study has found.

Buzzards, kites, harriers falcons and sparrowhawks were all attracted towards turbines – putting them at risk of getting killed by the spinning blades.

Raptors are thought to prefer flying near tall structures during high winds during migration routes as they feel safer having a potential place to land during windy conditions, researchers say.

The findings published in Biology Letters said birds of prey like to migrate across narrow straits and sounds.

They are also attracted to islands and are strongly dependent on updrafts and thermals – rising columns of warm air which come off the land.

Several migration corridors for soaring overlap with the development regions for marine wind farms in north-west Europe.

Researchers, monitoring an area around a wind farm in Denmark said they found that ‘all raptor species displayed a significant attraction behaviour towards the wind farm.’

The birds flights were tracked by a combination of laser range finders and radar during the autumn migration in 2010 and 2011.

The greatest attraction was during times of strongest winds, according to the report’s authors, environmental consultancy DHI, Aarhus University and others.

Overall, birds of prey migrated 49 per cent of the time towards the wind farm, compared to 22.8 per cent and 17.2 per cent to two comparable sites that did not have wind farms.

In the most extreme cases, falcons flew towards the wind farm 65 per cent of the time, compared to 0 per cent to the similar site without a turbine, while harriers flew towards the study site 54 per cent of the time, as opposed to 0 per cent of the turbine free site.

In conclusion, the authors write: ‘The attraction behaviour suggests that migrating raptor species are far more at risk of colliding with wind turbines at sea than hitherto assessed.’

Raptors alternate soaring and gliding – and are known to show ‘strong avoidance’ of crossing large expanses of open sea.

By contrast, seabirds such as gulls tend to shy away from wind turbines – because they are more at home flying over the sea.

Henrik Skov of DHI, explaining the results told the Daily Mail: ‘It is probably that birds of prey are quite afraid of flying over open water.

‘For a raptor, it looks less risky to fly towards a wind farm than to fly over open water.

‘Sea birds, however, don’t experience the open water as being so hostile.’

The research was carried out at a wind farm in the Baltic, Rodsand II, on a migration route for birds of prey.

Wind farms in the UK are relatively new.

The first commercial wind farm – Delabole Wind Farm on the north Cornwall coast celebrates its 25th anniversary today.

Bird protection charity RSPB said the study highlighted how marine wind farm sites need to be carefully assessed.

An RSPB spokesperson said: ‘While we need to generate more electricity through renewable sources, this must be delivered in harmony with nature.

‘This new paper emphasises the need to look carefully at each site and the potential impact or risks any proposal may have on local or migrating wildlife.’

A spokesman for the wind power industry said survey work on stationing wind farms aims to prevent harm to wildlife.

Renewable energy trade association RenewableUK’s Executive Director Emma Pinchbeck said: ‘We understand that any power station will have an impact on the environment – for example, emissions from coal-fired power stations kill thousands of people every year.

‘So it’s all about minimising the impact of power stations and getting our priorities right.

‘The renewable energy industry is more aware of conservation issues than other energy technologies, and puts a massive amount of time and effort into measures to safeguard wildlife.

‘We always survey potential sites thoroughly before any construction work can go ahead, to make sure we won’t have any adverse impact.

‘That rigorous survey work continues for 3 years after a wind farm is up and running.

‘It includes a detailed analysis by boat and aircraft of individual species, population numbers and breeding patterns in the area.

‘We will continue to do our utmost to ensure that wind farms and conservation go hand-in-hand’.