If you choose your place carefully and camouflage it from humans, you can get away with it. I like to set mine low, with overhanging limbs, so a person can't see it without stooping. Just don't put it in an obvious place, and if you have to wade poison ivy or bust thick brush to get to it, most people won't go there. Humans always take the easy route. It helps to have a small camo one like the ScoutGuard, with no visible flash. Mine's not on public land, but it might as well be. I've gotten pictures of several people who never noticed the camera. Sometimes I have trouble finding it myself- that's when I know I have a good setup.
Killdeer, it's OK. I do it all the time!