It can be very difficult to tell a rooster from a hen until they are almost fully grown. There are certain types of chickens that have been developed to make it easy to tell (the males will have something different about their color from the females) but for the most part it's pretty much a guess... When we bought our 4 chickens we didn't know anything about them and just took the word of the lady selling them that they were all pullets (young hens) and not cockerels (young roosters). Things were fine for months and I came to have a favorite hen - Maude. She had more personality than the others and, even though she was the smallest, was clearly the leader. Maude loved adventure and had no fear of striking out on her own to explore new territory. Looking back it should have been obvious but it never crossed my mind that Maude was fooling us until one morning I heard someone in the coop honking instead of the normal peeping and clucking. I was very worried at first that it wouldn't work out having a single rooster with just three hens but, so far, everything has been fine. I thought about changing his name but nothing else would do - he was just Maude and no other name would do. Here is his transformation: