Quite worrying, since we all love birds, but partial solutions suggested:
https://e360.yale.edu/features/bird-window-collisions
https://e360.yale.edu/features/bird-window-collisions
It's not the least charm of a theory that it is refutable. The hundred-times-refuted theory of "free will" owes its persistence to this charm alone; some one is always appearing who feels himself strong enough to refute it - Friedrich Nietzsche