I don`t know what it is but they know where you do not want them to go and that is where they go. I did the same as you. I let them free range until on day they dicovered the one neighbor that is close.I put up poultry netting to keep them from going there but they walked around it. All of my other neighbor are far away. I can not even see their houses from here. The neighbor did not mind and thought it was cute the way the roo would walk with me to the mailbox. Chicken will tear up a flower bed so befor it got to that I decided to pen them up. I did not want to but what are you going to do. I feel bad cause I have plenty of land.