I have the same situation, except with two nests in boxes that are about 25 feet apart. This is the first year I have seen this behavior. They started building in one box, but after only one day a HOSP pair decided to take over the box, so the bluebirds moved to the other box. Then an even stranger thing happened. After two days, (and NO nest building) the HOSP pair just decided to leave! I have never seen this happen before, and I don't know why they moved on. (Maybe they could read my mind that a trap was in their future??) But I think this is the reason the bluebirds are building in both boxes - to try to control the territory. It will be interesting to see which box they choose.

My Blues nest is done here but I do not expect an egg until the week of the 26th. In 6 years that has always been the earliest, one year I didnt get one till Mothers Day. Don't worry if they take their own sweet time they will eventually "get busy" LOL!

Sounds like you really have some challenges. You have my sympathies! A tiny poked hole is more likely a house wren's thin sharp beak, sometimes taking them some distance away, or simply tossing them out. The house sparrow will toss the eggs out, but their finch-like beak would not as likely make a tiny poke hole. And the HOSP is more likely to stick around, harass, or even take over the cavity. "Do BB's destroy their own eggs" ... No "the nest possibly could have been flooded?" ... are there leaks that could be fixed? "Are the HOSP really sneaky" ... yes, but HOWR are sneakier ... "and resistant to the Sparrow Spooker?" ... yes, and house wrens will not be deterred by a sparrow spooker. House Wrens are even sneakier, faster and silent, leaving no evidence behind, only destroying eggs or young. You might hear them singing, but might never, ever see them! There are some links to sound files of house wren song and chatter on Bet's web pages, so you can learn to hear the unwelcome sounds of house wrens. Visit Bet's web page for more info. And by the way, the Carolina Wren is a very different bird, welcome almost anywhere; not a threat to other birds. BlueBars Here is a link that might be useful: http://www.sialis.org/index.html

No Tim. That has not been my experience. If a completed nest with eggs is predated, my experience has been that the Mamas will build another nest to start over. They don't reuse the old one. If there is an old nest inside the box, they may build a new one on top of the old one. It's best to clean out all used nests once they are done with them. Tim (#2) was recommending that you keep the nest if it is still intact in case you may have a need for it in the future.~~Angie