Sounds like you're doing all the right things to protect them, so hopefully it isn't the work of a HOWR. In my experience (especially with my pet birds, but once with TRES)sometimes a baby will just die. It could be that after the live young fledge, you will find an egg and a deceased baby under where the lively nestlings were. You may not notice anything wrong, like flies, because the deceased nestling was so small. From your timing I'm guessing these are recently hatched? Please feel free to correct me if I'm wrong.

Rebecca, I am a bit confused about your timing. So, you think the eggs hatched around about June 4th, and the babies would be 3 days old today? You know for sure that you had 5 eggs, and you are now only seeing one unhatched egg and two healthy babies? It's not unusual to have an unhatched egg, so that is really no worry. I do wonder though where the other 2 babies are. It really does cause me to worry that something got them. They would be so small yet that you should be able to see them in the nest. The question would be: what in the world could get them in a box with a baffle, spooker, and a wren guard? Hmmm..I wonder what Donna will say. You don't have to worry about the remaining egg. If you can get to it easily, you can use a plastic spoon and very gently remove it, trying not to touch the babies. Otherwise, just leave it as it won't hurt anything by being there. Sorry I couldn't be more help. I'd just keep a close watch on that box.

I beleive your babies started hatching on the 2nd as per a previous post, correct? So when you posted this they would have been approx 5 days old? Could you still see the unhatched egg in the nest when you checked and thought you only saw two babies? They don't always gape so if you took just a quick look could it be possible the other two were just lying there and you just saw the two heads up and maybe the other two were down? I would check again and look good so you can tell for sure what you are seeing, sometimes it is hard to tell for sure though. I have no clue what could have taken them though if in fact two babies are gone. With a sparrow spooker, wren guard and baffle you would hope they would be safe. But I guess we never know for sure. Hard to say if the adults would remove them if they had died. I once had a baby with a deformed leg and the parents stopped feeding it. They also did throw it from the nestbox when it was about 4-5 days old or so but that was all they could do was toss it out of the hole, then they sat there fussing like crazy until I went out to see what was the matter and I removed it from the ground below the box.

As for the unhatched egg, I would just leave it. We often have unhatched TRES eggs and they are fine and just removed with the nest after fledging, also happened once with a Blues nest and a Dees nest...one unhatched egg. I just let them be.

Good luck, I sure hope the remaining two make it to fledging!!