Climate minister Rob Jetten will ask energy companies to slow down their wind turbines on the North Sea twice a year to prevent thousands of migrating birds from being killed by the fast-turning blades, according to a report by press agency Bloomberg.

Expert estimate that the turbine blades kill some 50,000 birds every year as off shore wind farms proliferate on their migratory routes.

Students at the University of Amsterdam have developed a model which predicts when the birds will be on the move two days in advance so energy companies have time to adjust the rotation of the blades.

‘During migration birds travel across different landscapes, many of which are dominated and created by man. That leads to conflict,’ researcher Fiona Lippert said.

The two day warning will keep the loss of wind energy to a minimum as energy interests and ecological interests are weighed against each other, she said.

The early warning system, which slows down rotation to almost a standstill for as long as 12 to 48 hours when the birds are approaching, is currently being tried out. No warning of great numbers of birds on the wing has come in so far, ‘perhaps because the birds have chosen a different route or have not started their migration yet,’ a ministry spokeman told RTL Nieuws.

If the trial is successful more wind farms will be included in the project.

On land, wind farm Krammer in the province of Zeeland, which is home to the osprey, is the only Dutch wind farm to use a warning system to prevent birds from being killed.