[steve86]

they are flying along just fine until they fly over heated asphalt, the air is thinner and their altitude drops suddenly)

Not quite LOL. Ask any sailplane pilot. The heated air rises as a thermal and the birds (depending on species) use it either to ascend or to not have to flap their wings as hard.

[ransomnote]

So they really are trying to kill us by driving their beaks through the windshield!

But heated air is less dense. It’s freaky how many times I’ve read the classic “Parakeet got out of his cage, flew around the room and landed in the fying pan that was in use.”
And the drop of birds over hot roadways.

I think sailplanes and these bird examples have some differences. I agree “hot air rises” but there’s the “and it’s less dense” problem.