Tumbleweed writes

Thats another factor, cats, though I dont know if there are more than there
used to be.

Shouldn't think so.

And windows. There must be a lot more, and a lot larger windows
than say 50 years ago.

Yes, but the window owners feed birds much more than they used to.
The cat owners tend to as well. We do.

Windows are responsible for huge numbers of bird
deaths every year.

Yes, but they very soon learn. One gets the odd few bashes when birds
first fledge, unless cat gets stunned bird they seem to recover quickly.
After that its rare unless spar is about who has learned that spooking
birds to mindlessly flee at speed through a window makes for an easy
meal (seriously).

--
Oz
This post is worth absolutely nothing and is probably fallacious.
DEMON address no longer in use.