I don't know, maybe because of the massive amount of smoke they are breathing in, it's too damned hot for them, the magnetic poles have shifted enough that they can no longer navigate correcty, increased temperatures have brought some fatal disease to the flocks, etc. etc. etc. Even the article posits that the birds didn't have enough time to store enough fat before getting pushed out by the wild fires. Misleading headline.
Probably because the planet is fucked?
This comment was edited on Sep 15, 2020, 18:47.