Donna and BlueBars: I agree with you on the 1 3/8 inch holes don't seem to help deter the house sparrows, maybe they help deter larger birds. But for some reason people started building blue bird house with the 1 3/8 inch holes, me being one of them. My gut feelings is it is to help deter larger birds other then house sparrows. I did find this below while continuing to search sialis site. Minimum diameter for House Sparrow entry according to this web site I probably could reduce the hole another 1/8" to 1 1/4" on the oval holes. I wouldn't want to get any smaller then the bluebirds might look for other nesting boxes in the neighborhood for a box with bigger holes. I might try making some with the gilwood hole or a slot at the top of box. Looking at trying to make and sell a few houses for sale, don't want to be telling someone something that has been proven false or isn't really true. Documentation helps on that. Keith

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

My guess is they are cowbird eggs. Very gently remove the brown speckled eggs (as not to crack the bb eggs) they will hatch before the bluebird eggs do and will eventually take over the nest box and the baby blues probably will not survive. I get them in the poor chipping sparrows nest and the cowbird babies are bigger than the nest. The chipping sparrow eggs are thrown out of the nest by the baby cowbirds. Karen

It's good to hear that you have properly mounted your nestboxes with baffles. Your Blues will be much safer in their future nestings. Good luck in the return of your Blues. Also, you may want to think about either making or buying a sparrow spooker if you have house sparrows around.