Wind farms come with many benefits - but they can be a danger to local birds. A new study suggests a small tweak to the turbine design could make a big difference in terms of avian safety, and all it takes is a paint job. In an experiment run on the Norwegian archipelago of Smla, changing the colour of just one of the turbine blades to black led to an average of 70 percent annual reduction in bird fatalities, as measured over three and a half years. In a linked experiment, painting part of some of the turbine towers black also resulted in fewer bird deaths. While the study only involved one wind farm and a small number of birds ... it points to a way of keeping birds from harm without major reengineering. In this case it was resource demanding to paint the rotor blades, since the wind turbines were already installed," says conservation biologist Roel May. "If the painting is done before construction, however, both the cost and the bird mortality will be reduced." Very little data is available on just how many bird deaths are caused each year by wind turbines. Some estimates put it at the tens of thousands. Painted blades could be one solution to the problem. The researchers think it makes the turbines more visible to birds, reducing what's known as motion smear - where moving objects are more difficult to get a visual lock on. The study also looked at other possible ways of reducing bird deaths, such as covering blades with ultraviolet paint, and positioning turbines in such a way as to avoid areas of updraft that birds use to soar.