OK, I will probably get yelled at but, shake the crap out of the brown/white egg so it won't hatch. It is a cow bird egg and it will hatch b4 the bluebird babies and take all the food. The bluebird babies will have little chance of survival.

Karen

Hi Laura. What size hole do you have? A cow bird shoud not have been able to get in to a regulation blue bird box. (though birds dont aloways follow rules). Please Please shake shake shake that egg. Be careful to NOT break it then put it back in the nest and leave it alone.DO NOT destroy it as the Cowbirds may come back and get the Blues eggs for revenge. There are plenty of Cowbirds laying eggs in nests we dont see, they are in no danger of being endangered. If that egg hatches guarenteed some of those Blue babies will die of starvation.
Have you been to the sialis.org website to learn how to keep your Blues safe? If not please run dont walk. Good Luck!

I have a regulation size box....can't remember, cause I bought it 3 years ago, but I believe that is 1 1/2" diameter hole. Yes, I love the sialis website and checked it out before I posted here. That website and this one have truly taught me everything I know about bluebirds. But I wasn't sure that cowbirds are in SC (it appears they are, huh?). I guess it is the lesser of 2 evils between that and a house sparrow egg. I know that they are protected so you can't just make an egg conveniently disappear (or can you).....but I wouldn't want to risk revenge by the cowbird. Oh, I dread shaking that egg too. I surely hope it keeps it from hatching and doesn't hatch some mutant from all that shaking.

Oh yes we have cowbirds here in SC, flocks and flocks of them. Every so often in the fall I believe we'll get flocks that are very loud and go house to house I'm guessing before roosting in the trees or migrating, I dont' know. Every now and then also we'll have smaller flocks that swarm and invade the feeder. Luckely I've never had their eggs in any of the finch nests or in my one blue nest.

I sure hope that cowbird egg doesn't hatch or the baby blues will probably die. I would watch it closely and if it does end up hatching even after you shake it, I would certainly remove the baby. Cowbirds are like parasites. Actually I would probably leave it for awhile but them remove it closer to when the baby blues are due to hatch, that cowbird egg will hatch first.

Good luck.

Donna

A local bluebird fan told me that she also read about piercing the cowbird egg with a needle to assure it doesn't hatch. I believe I will shake and pierce....and hopefully not break it. Should I wear rubber gloves to keep my human scent off the egg, or is that not necessary?

Laura - I completely removed a Cowbird egg from a nest last year just a day after it was laid and there was no retaliation by the Mama Cowbird. From what I understand, they lay and move on. Is your box spooked? No other birds in my yard will go near my Blue house since I put the spooker up. You could remove the egg (I think we'd all rather deal with an unhatched egg rather than a baby bird...) and the spook your box. Your Mom Blue won't be scared off at this point, but it should keep the interloper Cowbird from checking up on Jr. Good Luck!!

I've heard the stories about the cow bird monitoring the nests where she has laid eggs, and I don't believe it really happens. Cowbirds used to follow the buffalo herds and could not stick around to raise their young. So they would lay their eggs in the nests of others and then might stick around or might move on, based on what the buffalo did. Yellow Warblers will build a nest on top of their original nest if a cowbird laid an egg in it. Naturalists have seen up to 10 yellow warbler nests built one on top of the other to avoid incubating the cowbird eggs that were laid in each additional nest. No harm was done to any of the warblers eggs and no retaliation was reported. Many birds naturally recognize the foreign egg and remove it from the nest, without any reprisal.

Lisa, it's a tight squeeze but a female cowbird can enter a regulation size bluebird entrance hole. Thankfully, it doesn't happen often and it's never, knock wood, happened in one of my nest boxes.

Cowbirds generally drop their eggs in another bird's nest and move on.They are not known to stick around and monitor it.
michelle

Find a HOSP or EUST nest and freeze the other eggs and let the cowbird egg hatch and watch the HOSP or EUST raise a cowbird baby.

Tyler, 22, West Central OH

I would not shake and pierce b/c it will probably leak and make a mess in the box and attract unwanted predators. Either just shake it or remove it. I'd remove it.
Cathy

Oh Tyler, you are too evil, I love it!

Oh, guys! Be careful on this! Cowbirds are federally protected under the Migratory Bird Treaty Act! That means it's against federal law to damage or destroy the eggs. I'd recommend leaving them alone. Cowbirds are native birds who need to live too, and you don't want the feds after you!