I have 9 chickens that have been laying for about 9 months. Today one of the eggs is so small it looks like a bird egg. What could be wrong. Even when they first starting laying the eggs were never this small..
It can happen. Often called a "fart egg". I got one myself about a month ago from one of my gals that normally lays rather large eggs. I cracked it open and it was perfectly formed just tiny.
No, it's perfectly normal and nothing to worry about. I've gotten quite a few of those over years and I leave them on the counter to dry out (takes a few weeks) before giving them to non-chicken owners as a novelty. See #14 here for more info and causes: