I don't usually see them during daylight hours. They do love to clean up the excess birdseed, find water, eat whatever they like and knock everything over looking for grubs and worms. I have a six foot chain link fence that keeps them out of the back, but they're regular night visitors to the front.
My neighbor planted 100 tulip bulbs, then goofed and left his gate open. He said it looked like his whole yard had been plowed. He ended up with about three flowers.
Yes, they can be dangerous--to people and dogs. I've heard that over most of their range they're not a problem in urban areas, because if they do show up they get eaten. Can't do that here!