Wind turbines are killing many thousands of bats contributing to a population decline that may be costing farmers millions of pounds, say researchers...... Scientists found the blades of wind turbines were a major threat to bats particularly when they are migrating.....Bats are useful to farmers because they eat large numbers of crop damaging insects, reducing the amount that has to be spent on pesticides....... Writing in the journal Science, the researchers estimated that bats could be worth billions to agriculture around the world. ......Several migratory tree-living species of bats were being slaughtered "in unprecedented numbers" by wind turbines, said