We have a couple of families of tree swallows that have taken up residency in bird houses in our back yard.  They are such fun to watch.  I think there is only one baby yet to leave the nests.  He appears to be afraid if height. 🙂  Last year I saw one that would come out a little ways, look down at the ground and go back inside.  Then he would repeat the action.  I figured he was thinking it sure was a long ways down to the ground.  I had to leave and by the time I got back he had apparently gathered his courage because he was gone.  Of course, his parents and siblings were hanging out on a nearby branch chiding him for all they were worth.  That was probably embarrassing.  Looks like this one is going to follow suite.