Total myth
Domestic cats may carry 2.4 million dead birds into the house as gifts. Bit no vcat can catch a bird that is able to fly., In realty the annul death toll of hatchlings *has* to be around 90% for small birds, or we would be treading on them. People in towns never find the dead ones until, cats bring them in. Out here since I have got rid of the cats there are dead birds everywhere...or piles of feathers.
Windmills account for
But what windmills kill are protected raptors and bats, because they generate updraughts and shock pressure waves.
And people. Never parachute into a wind farm.
Depends on what its treadmill is attached to