Is it possible for a 13 week old chick to lay an egg? I have 2 13 week old chicks, yesterday I found a tiny egg in their run. I let them out to roam with the big girls and sometimes the big girls will go into their run, and I just found out from my daughter, into their coop. I did find a large egg in the little chicks coop that I know was not layed by them, but this little egg has me wondering, I mean it was just laying on the ground, my big girls don't usually do that. I just don't know Who laid it.