We live in a fairly densely populated urban area with 6’ vinyl fences. Our entire lot including the house is just under a quarter of an acre. We set aside a good part of the yard for the chickens. My question is, do I need to worry a lot about predators? If so, how much and what kind? The coop itself is pretty impervious. My main concern is during the day. Are they ok to free range or should I have them in a run?