I didn't think I would be writing any more about the birds, but now there are 4!  Doug thinks the new ones may be the babies; they are fluffier than the others.  Someone had mentioned about putting an owl up there to scare them away.  While showing our visitor from Tucson, Dorothy Moore, around the town square, I found a couple of small ceramic owls.  They didn't look a bit scary, but I had to have something small to fit on the ledge.  We put them on the ledge in front of the door, and sure enough it worked.  They moved to the other side of the porch!  Last evening we witnessed a domestic dispute between the probable parents birds.  The two new birds sit very close to one another, facing each other.  One of the older birds had settled in the corner and snapped (if you can call it that) at the other one trying to get near.  They both flew away for a while.  When we checked later, the two older birds were in opposite corners.  But at least they are away from the front door.  Who knows, when we get back from our trip (leaving next week), we may have a flock of barn swallows.