I'm pretty sure domestic cats kill more birds than windmills.
The number of birds killed by windmills is likely somewhere in the six figures annually. https://www.smithsonianmag.com/smart-news/how-many-birds-do-...
> In the end, using 58 mortality estimates that met their criteria, they came up with an estimate. According to the current literature somewhere between 140,000 and 328,000 birds die each year from collisions with wind turbines.