I cannot answer that, maybe someone else can. I bought marans hatching eggs to put under my broody hen, and she took right to them. And the funniest thing happened this morning. I opened the cage to see if she wanted to get out and about for awhile(she did, but came right back after a few minutes). After she came back and was settled, before I shut the door to the cage, another hen went into the cage to investigate. I thought there may be trouble coming, but no, the other hen went in behind her, laid an egg in the corner of cage and promptly left the cage! This is a small light blue egg, and the broody hen gathered it under her! So I don't know if it is fertile or not but guess will just leave it alone and see. My roo is a cuckoo marans and that little hen is a small gold and cream colored Ameracana, so who knows what that little bitty may look like!