Scot, day 20 after hatching is quite a long time, but I’m sure it has happened before. 17-19 days is the norm I believe, so it is not much behind. There is not much you can do at this point except wait, especially when parents are still feeding it. As far as them beginning another nest in a not so safe box, that, too, is pretty much something you have no control of, especially if there is an actual nest began. Sure hope that lone baby flies away in a day or so! Drama for sure . . . .
