I roll the big magnet over the ground near the barn and coop every year, and find amazing things (old farmstead). It's hard to manage every single nail/ screw when building, and they reappear every spring! One nail can kill a horse, not to mention the chickens, and I'm paranoid about it. That...
I've had birds trapped behind things, in the coop and in the barn, sometimes with a sad ending. Every night when we lock up the coop, we do a bird count, followed by S&R by flashlight if needed. Mary