I have chickens that are free range & they do go into the neighbors yard. I have talked to them to see it they have a issue with that. They don’t (they are an older couple) & actually feed the chickens & guineas because they enjoy watching them. You want to have good relations with your neighbors but they don’t seem to care and You shouldn’t have the expense of keeping their chicks out of your yard. I would tell them again to keep their chicks at home or your going to report them.