I hang a disc shaped hummingbird feeder about 12" away from a window (in the shade). sometimes they fight, and there have been a few times one bumped into the window during the scrabble. (it's not a picture window. they've never collided from far away.) I've never seen any signs of one being stunned, but I worry. I tried putting special UV reflective decals on the window so they know it's there, but it didn't seem to help. I think they just get confused while fighting.

do you think it would work to hang the feeder so it's touching the window, so they have no choice but to perch / fight on the far side? window mounted feeders seem to be common, so maybe they're considered safe?

or maybe I don't need to worry about it? I have a theory that maybe they're striking from so close they can't really gather significant momentum.

any advice would be welcome. tagging gardengal48 (PNW Z8/9) and annztoo since you seem to know about birds!