According to Wikipedia, domestic cats (most "unowned") kill 1.3 billion to 3.7 billion birds each year in the U.S.
Meanwhile, according to the Audubon Society, wind turbines kill an estimated 140,000 to 328,000 birds each year in North America.
According to The Guardian, at least 100 million and maybe as many as a billion birds die each year in the US when they collide with buildings, especially glass-covered or illuminated skyscrapers.
"Aldous J. Pennyfarthing" (can that be a real name?) blogged about Trump's claim, but does not include that kind of context. Rather than just mocking Trump, I think it would be useful to put things into perspective for readers. It may be possible to educate a few people here or there.
It's one of my many editorial pet peeves ...
I know debunking Trump is an arduous and perhaps thankless task, but share those figures if a Trump supporter makes a claim about piles of bald eagles under windmills.