Some of my small flock has started going next door to the neighbors. They only do this when there is not someone in the yard. I do herd them back into my yard as soon as I see they are over there. When I went to bring them home yesterday I noticed what look like mothballs on the drive. Then I saw that they have placed about 3 eggs randomly in the yard. I know that they are not my eggs because they are white and none of my hens lay white eggs. Any suggestions on how to keep them in the yard other than a fence.