My chickens (silkies) are both assumed to be related and from the same batch, since they were around the same size and have been developing at a similar rate since we got them, and also the lady said "this is the mama" about one of the chickens the day my boyfriend went to pick them up. So, if they are, then presumably the differences between my two chickens could be used to sex them? We know for sure that Jacob is a cockerel, because he crows. But the week prior to him starting to crow, I was able to guess that he was most likely male based on his physical features. He is at least double Claudie's size, his tail feathers are long and they curl down, his pomp/headfeathers are not as rounded as hers, and he has a much larger and more noticeable wattle and comb. He's also less friendly. So, since it's now confirmed that he's a male, can we safely assume that Claudie is female? She hasn't laid any eggs yet, but she's also not crowing. They're only around 17 weeks, so it could be months until she starts laying if she's female since they're silkies.