First thing that comes to mind is a House wren, they can and will poke holes in other birds eggs and throw them from the nest. However they normally don't leave any left, the will poke them all and or throw them all out. Unless it got interrupted while doing so, if the Blues returned and chased it away. The Bluebird would not normally take an egg out. There are many times one egg doesn't hatch for some reason and they just leave it right there and don't ever take it out. I would keep any eye out, hopefully they don't give up on the two remaining ones but if it was a wren it will probably be back. Good luck! Donna

Do you have any other boxes up that they may be interested in? They may make another nest in another box. I would leave the nest as is and if you see no changes after a week or so remove it. Birds are unpredictable sometimes. Maybe the eggs were not viable or you are looking at a new female. Maybe HOSP or another predator removed an egg.

What mlkbskt said is correct. A nestbox should never be mounted on a fence/tree or post of any kind unless it can be baffled. Conduit works best for mounting nestboxes on and stovepipe baffles are cheap and easy to put up. Nestboxes should also be put up at least 15 feet away from any trees. With just one egg gone I would think either House wren (are they in Texas?) or House Sparrow. The House Sparrow will usually just go in and smash the eggs and or kill babies and adults that may be in the box, however it could have gotten interrupted by the Bluebirds too. That is why a sparrow spooker is very important to put up after the first egg is laid. Sparrow spookers are easily accepted by Bluebirds. Wren guards are a little trickier though but do help if wrens are in the area. It is best to put them up during egg laying though to make sure they are accepted. The whiter end and ring on the egg is normal, I have seen it before too. A mockingbird would not be able to get into the nestbox so it would not have taken the egg. Is the hole on your nestbox the 1 1/2 inches that is standard for the Bluebird nestboxes? It shouldn't be larger to prevent Starlings or Red Bellied Woodpeckers from reaching in and grabbing eggs or babies. As far as the heat, I know it can kill nestlings if it gets too hot but not sure about affecting hatching, normally the Momma just wouldn't need to incubate as much. Day 15 is not out of the norm, I have heard of eggs going up to 20 days and still hatching. So the eggs can still be good, but if something got one chances are it could come back and get the rest. Raccoons love to reach into nestboxes and pull out babies/eggs and incubating female but they usually do it at night so the momma would be gone/eaten and probably all the eggs if it were a raccoon. Raccoons are everywhere even if you don't see them, they are there! I would keep a close eye on the Blues and see what they are doing. Are they still going to the box or not? Usually they will not give up on the nest if an egg is taken like that, so the nesting should still be ok and also they can sit on eggs a long time before they give up on them. Good luck, hopefully you can get this nestbox safe and can have a successful second nesting. Don't let the first nesting fool you since it was successful, an improperly mounted nestbox is a failure just waiting to happen. Read up at sialis like you said you were, there is tons of great info on there! Donna

or the blasting heat...... Miss my fresh KY wonder......um yum yum and fresh yellow squash and zukes.... still got some mustard greens going in my two raised beds... and those were from the bolting ones that dropped., seeds Yummm Yum... Nothing like your own greens... I would have planted more if I could find my open packets of kales, collards, mustard greens. seeds...Hecks its been so unseasonably warm they would have did just fine in my "potato bins" If Hubby ever gets the time or energy. (Unfortunately I bought some feather girls and they take so much time,,,,,) May get a greenhouse.. got plenty of windows to do it... Just need the time...and energy even bought the larger outdoor unit " Hardy"to heat a greenhouse. but Hubby cant do it all Unfortunately he planted close to the house so smoke comes in some ... I know he does so much already. Just a wishing