So sorry to hear of your poultry 'challenges,' but I can relate as I also asked that same question last fall....why are they so stupid? Curiosity...birdbrains...jury is out....
My short story--small flock free ranging in our back yard last spring, neighbors little dogs (terriers) escaped and came over to spook the girls...no harm, no fowl (ha), no damage done, dogs caught (great neighbors, no issues here), and we managed to herd most of the girls back into their run, except for Phyllis, our llittle Polish hen, who chose to scoot away. I let her go as I was hanging laundry and she headed to the back of the yard...ends up that was the last time I saw her. Went to look for her a short time later, we were all checking everywhere, barn, fencerow, pasture...nothing. Felt horrible as I was the last who had seen her, I should have gone after her but we figured she, with her poor vision, had been a hawk's lunch. After two days of searching, finally gave up...but still kept an eye out for her...hoping. Well, when another load of hay was to be delivered my dh went out to re-arrange the older hay late this fall...moved some bales and found..yep, Phyllis. Well, sort of...more like a puffball of dried up bird. Seems like she had somehow flown up into the stacked hay and gotten stuck between bales...no idea how she got and felt (feel) horrible that she died the way she did...but we had no idea. Life goes on and we learn as we go...but never would have thought. Sigh. Anyways, live and learn---sort of like having a 2 year old visiting., got to poultry-proof your garage now!