The billion birds things seems to go back to one single "study", and there already seem to be doubts about it https://www.npr.org/sections/13.7/2013/02/03/17085

The billion birds things seems to go back to one single "study", and there already seem to be doubts about it https://www.npr.org/sections/13.7/2013/02/03/170851048/do-we-really-know-that-cats-kill-by-the-billions-not-so-fast https://www.npr.org/sections/13.7/2013/02/03/170851048/do-we... (although I think npr is a weird source, I don't know). In any case, those are probably just napkin calculations. And I bet I can find a wild variety of estimates for birds killed by wind turbines, too - depending on whether the person doing the estimating wants turbines to succeed or not. It seems likely they don't kill the same birds as wind turbines, either. And not in the same locations. All in all the comparison might just make not much sense to begin with. How many birds are being killed and eaten by humans, for example? Probably several billions more, but they are not the same birds that are being killed by turbines.