Ignoring the terrible price we all have to pay for the subsidies in order to pay for the wind farms, and all the politicking, it boils down to this.
Before Wind power: An oil, gas, or coal power station chugs away producing electricity. Birds fly around in the sky.
After Wind power: An oil, gas, or coal power station chugs away producing electricity or idling for a bit waiting to provide back-up electricity, constantly instantly varying the quantity it produces to cover for windless days, hours or moments. Birds, sadly including some very rare ones, get chopped to bits on those occasions when the wind turbines are turning.