Donna is right the guard may not work since the Wren knows it's there. One other thought is (when the first egg is laid) to turn the box 1/4 turn, you will have to watch to be sure mom finds the hole and not the Wren. As soon as Mom finds it put the guard up making sure there are sides on the guard so the hole can not be seen from the top of the box. Again make sure Mom finds it. Last ditch effort would be to move the box entirley in plain view of the Blues. If none of this is successful the worst that will happen is you will lose the eggs and the Blues will nest again. Also get a high powered water gun and attack the Wren whenever you see it near the box. Good Luck!

I discourage the wrens. I take any sticks they put into a box away as quickly as possible. From the information I've read on the Sialis website, if you let wrens nest, you will soon be overrun with wrens. The wrens will poke holes in the Bluebird's eggs, or toss out their chicks. So if you're trying to get Blues, I would certainly discourage the wrens.

Thank you both for your help - no need to apologize Kendra, I wasn't sure what help I was asking for! I am still so new at this I am afraid to take an action such as remove a nest. But I am going to do that today. The chickadees in our yard are such a joy, I feel very protective of them. And having seen the wren take over a second nestbox confirms what I was thinking. I will check the first nest for eggs/nest cup and if they are not there the nest will go. As for the second nestbox, it's in a tree so will take some time to check! connie-k - Keeping the wrens busy is a great idea. The only problem with that for me is that our three nestboxes are within eyesight of each other, so encouraging wrens to stay in our yard would not be good. Right now I am contemplating moving them farther apart, so I will keep the gourd tactic in mind. I will let everyone know what happens in the end, whether I outwit the wrens or they fool me...da da da daaaaaa.....

We've had a house wren building her nest for the last week so decided to close the hole. I feel better knowing that you have boxes close together. I'll look up info on Tree Swallows and other cavity nesters with regard to the location as well as what other birds will be happy with a bluebird house. This box is at the very end of our yard next to a berm and not as easy to monitor (from our house) as is our original Bluebird house. I thought by closing up the hole, for right now at least, they could use it as a perch. Thank you for the ideas. Both sound promising and our hard work may pay off as well.