We simply put up post it stickers where birds usually crashed in our windows. There's way less crashes and dead birds after that.

Think how many birds crash during a year, and how many houses and buildings with windows there are.

You can also buy bird stickers to put up.

I have to leave my windows dirty so the damn birds stop smacking into it.

Furrows the brow of my wife up quite a bit.

For folks at home thinking about their windows: Apparently one issue is that windows may mirror the outside environment to birds, appearing as portals to more open-space and trees, especially if you include ultraviolet light which humans can't see and which the glass wasn't designed to pass-through.

So there are a variety of products advertised for home usage that stick to the outside of the window to make it appear more like a barrier, often semi-transparent to us but more-opaque in ultraviolet to birds.

Earth at Night in Colour S01E05 touches on this.

The subtitle is revealing:

[We don't know how much birds kill the windmills so] "This makes it a weak argument against windmills"

"We don't know how much, so it may not happen, or is not so relevant as we think, but is repeated by ideology", is a nasty trick. Nice smoke curtain. Specially when is joined later with:

"it is true that all humanmade structures are technically bird killers, but..."

Either it happens, or it does not happen.

We aren't talking here about a sparrow crashing against a window. What we do know is that carcasses of big raptors, vultures, storks, other birds, and even bats can be found near the windmills basis often, in a distribution that is not aleatory.

Even if we never achieve to calculate an exact value (before the corpses are quietly removed by foxes or companies) we can identify that there is a problem here. As predators are scarce (by definition) and some are endangered, the impact on populations is not negligible.

Killing endangered species is illegal. It does not matter If is "just one" or "just a few" eagles.

Why does this matter? They’re just drones! Birds aren’t real! [1] /s

[1] https://en.m.wikipedia.org/wiki/Birds_Aren%27t_Real