One of my eggs from under a broody hen just hatched even though she wasn't supposed to hatch til next Thursday (6 days). I definitely didn't get the date wrong and I checked the other eggs by candling and they look on target for around 14 days. There also aren't any hens in the coop with her that could've laid another egg. The chick is perfectly healthy and one of the strongest I've ever hatched. I am stunned that a chicken could hatch this early. Has anyone ever had this happen before?
