I have had 3 pullets/hens crow, young Buff Orp, Bantam and I think maybe it was my 2 yo. Barred Rock, could have been my Brahma after I removed a rooster (by that time I was no longer surprised or amused i'm sure). I guess I used to think it rare too lol. I am in a sunny warm local, I don't know if that has anything to do with it, I was rooster-less and we have feral roosters crowing in the distance. Seems crowing is a sounding board for the who's who and where everyone is at around here, so they can fill in the blanks. Now that I have (several) roosters my hens don't crow any more. With that said, I don't remember my Brahma pullets being so dressed up at 4mos unless a cockerel. But they do have the best crows comparatively IMO. Very good looking feathered kids.