I have a barred rock chicken in my flock that I've been questioning for a while now whether it's a hen or roo. Lafaunda is 18 weeks old, and her comb and waddles have developed faster, and are a lot more red than the other girls. She's kind of grumpy, is the dominant one of the group, and is always squawking at me. I don't know if that matters lol, but thought I would share that also.
The last pic is one of a different hen to show what the other ladies combs/waddles look like
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If she's really 18 weeks, then perhaps she's getting closer to laying her 1st egg in the next couple weeks. A roo would have a bigger comb by 18 weeks.