Can I swap eggs out under a sitting hen?

[crazy4eggsJulie]

We have a blue marans hen who has been sitting in a nest box for around 12 days now. Recently, our egg collection went way down. One day when I went in the coop, another hen was in the box with her. I watched her lay an egg. When I went to get it, I felt two more not covered by the wings of the sitting one. A few days later, I finally lifted her up to find 12 eggs under her! I could tell that only two were hers due to the coloring of them. I know that these eggs would not be pure bred if hatched because our roo is a cochin. Can I buy fertile purebred eggs and exchange them out under her now -12 days into the process? Will she continue to sit until they hatch or will she realize that it is taking way too long?

Thanks!

 

[jeslewmazer]

Yes you should be able to swap eggs. Since incubation takes 21 days and hens don't seem to be very good at math. I experimented one time and let one hen set two separate clutches of eggs back to back. I made she her weight was healthy before and during the second clutch. At the end of the second clutch she started to get too small but she was done and raised that clutch. She sat for 39 days. If a hen fells the chicks moving under her then she knows its time. Depending on the hen....Example.....some only set for up to around 30 days and give up if they have no chicks. If you have the eggs handy I would say go for it defiantly if she is fully into setting.

 

[Sunny Side Up]

Make the swap after dark and the hen should accept them, she shouldn't notice any difference & remain on the nest another 21 days until they hatch.