We recently bought 25 4-5 month old chickens from a local lady. 14 of them are BO's, but we noticed that two of them have yellow legs as seen below. Are these actually BO's? They have a single comb, and their beaks are the same yellow as their legs. They're also a little larger than the other BO's even though their combs are slightly less developed. You can see that the other BO's in the background have more peach colored legs. Regardless of what they are, they appear to be a heavy breed, so they'll fit well into our flock.
