The risk of birds colliding with offshore wind farms is half the level previously assumed, according to a two-year study that claims to be the world’s most extensive.

The study – run by the UK’s Carbon Trust for 11 developers, seabed landlord The Crown Estate and Marine Scotland – spent two years tracking the interaction of birds with the Thanet offshore wind farm, a 300MW project operated by Vattenfall off southern England.

Researchers used a “multi-sensor monitoring system” combining “human observer-based tracking with a system that automatically recorded seabird movements”, with radars recording data 24-hours a day.