If another one is gone in a few days, you may have a black snake in the coop/shed, or with an access hole to it. It doesn't have to be a very big hole for him/her to get in, I have seen a photo of a black snake that had eaten an egg, and then didn't fit out the hole it came in by - half in and then 'corked' half out. One way to find the hole, I guess. I can't see a rat taking only one egg, though it might (try setting a rat trap where the hen can't get at it, to remove that possibility) and 'coons or 'possums would take the hen. The other possibility is that the hen accidentally broke it and ate it, but this seems unlikely.

My female is sooo focused! First nesting fledged (6) on Thursday May 10th, I got the nestbox cleaned out asap because I know this female is very quick to start the second nesting (she is the same female we had the last two years). She started the second nest on Friday and laid the first egg this morning! I couldn't believe only four days inbetween fledging and laying another egg! Dad is still busy feeding the fledglings which are in our woods, haven't seen any of them yet, hopefully by this coming weekend I will get some glimpses of them and maybe tell how many made it. Two were non flyers so I am not sure about those two, especially with the mom focused on the second nesting and not on her fledglings. Donna

Well If you have ever seen TRES fledge theres no way a baby Blue will make it. I would almost opt to candle the eggs and if there is little to nothing there get rid of them. Is it possable to tell the difference between babies at hatching time? I would want to put them in the Blues nest but that could cause problems too. Lets think babies not eggs here. No way a blue can survive with a TRES Mom, overloading a Blue or having babies hatch days before her clutch could result in dead babies. Yikes this is one for Bet, Malinda or Cornell. Im still thinkin destroy the eggs so no babies ever suffer.

Boy can I relate to your frustration. Those wrens ruin so many nests. Sorry about your Blues being chased out. Those wrens are just awful.