Six weeks ago I bought 10 5month old hens. After a week in the coop & run I opened the gate for them to free range during the day. All went well for about a month as they ranged over half of my 2 acer lot. About a week or so ago I noticed after opening the gate that the chickens would come out but only for a short time then return to the run and actually spend most of the day inside the run under the coop which is about 3 feet off the ground. When they do leave the run now they stay within 20 -25 yards of their home. I heard a hawk and saw one overhead a few weeks ago. Could this be what has changed the chickens behavior?