So I think I have this figured out. When I bought them the place also had broiler chickens and I think Big 'un must have somehow wound up getting mixed in with the amber link chicks. Def no complaints though. She is so sweet and docile.
My start with chickens was rescuing poultry plant chickens that fell off the trucks. We had one recently, but she didn't make it. We did, however, buy six little pullets to start our backyard flock. They are three weeks old now and doing great.
We have four three week old amber link chicks. One of them is growing way faster than the others. I'd say it is double the size of the others. We bought all pullets. Is it possible this one is a rooster or does it just happen to be bigger than the others?