I dunno, Marc, might wanna check the expiration date on your socks .. or something. It could also be a simple case of them just being bird brained. ;-) ;-)
Seriously, do you think it may be insects moving that they associate with someone or some thing moving through the woods? I have had and have Mockingbirds that will come to the lawn mower for just that reason. Sometimes they will watch from a branch and other times they simply sit on the mown lawn sometimes sorta hopping along behind or taking small flights and watching the mower to see what moves. All I have to do to get their attention is to start the mower. There are nesting sites on the place and I get both mature and young birds that will do this. I don't know, but you could almost say that it is passed from generation to generation as its been going on for over thirty years. Just a thot.
