We had a wren family build a nest in our bluebird house and she laid seven eggs. All the sudden one day the eggs were gone and they had been there the...
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WREN EGGS #758882
Asked June 28, 2021, 4:20 PM EDT
We had a wren family build a nest in our bluebird house and she laid seven eggs. All the sudden one day the eggs were gone and they had been there the day before. Then after a little while she laid six more eggs and one day they were there and the next day they were gone. The house had a zip tie over the top so the hinged roof could not be opened. The nest was undisturbed both times. We never found any egg shell fragments on the ground or in the nest. We are wondering what could be happening to our wren eggs. Is there someway we could’ve done to protect her eggs better? If you could help, that would be great.
Shiawassee CountyMichigan
Expert Response
Hello there, apologies for the delay in my reply, I was out of town for a week.
I can not say with any certainty what may have caused the disappearance of two egg clutches, but predators could be a possible cause. Racoon, outdoor cats (which are very harmful to native birds), Possum, or other small mammals can eat eggs of birds. The key way to deter this is to make sure the nesting box is designed properly. You nest box looks very nice, but the entrance hole may be too large, making the eggs more vulnerable to predators. For house wrens (the most common wren species to nest in nest boxes) the diamater of the nest whole should be no larger then 1". If yours is larger, then take a piece of wood with a 1inch hole and attach it over the existing hole. This will also create a deeper entrance hole and will provide additional safety. In addition the perch should be removed as this can assist predators and is not needed for the wrens.
For house wren nest box dimensions and additional information check out this Cornell University site. Here you can learn more, and learn how to help contribute your nest data to citizen science databases: https://nestwatch.org/learn/all-about-birdhouses/birds/house-wren/
Thank you for your response! We designed it according to online directions for a bluebird home, but the wrens moved in. We’ll alter it like you said. Hopefully she’ll lay eggs again. They’re still guarding it all the time & adding sticks to it. They really want to be parents! Thanks again!
