If they see a hen using the nest box, they figure that one is special. Then all the others think so too. Sometimes they will climb on top of the current laying hen, and drop their egg on her back. " Chickens are geniuses," No one ever said!!
I have a chicken that likes to go in to a bean feild . And you can't find him for like 5 hours after she will come out . She is the only one that does it to out of all 12