My Isa Brrown's are probably about 40 wks now. I got my australorps x RIR about two weeks after and they were a bit younger, so I'd say they are about 32 weeks. My other two are a bit of everything.....they have a bit of leghorn, RIR, RIW and australorp. I got the last two about three weeks ago. So they are probably 22 wks. There was some pecking order business going on..... And it was the Australorp x that were doing it to the new girls, nothing to savage. But it's the australorp x that are losing feathers around the neck, and I busted my other Isa brown (not the one with crop issues) pecking the feathers off the Australorp x while she just sat there, not bothered by it. So, I'm thinking maybe a protein issue? Or a bit bored, because since the last two arrived they have been confined to the run and not getting out in the afternoon for some free ranging. It's spring here so didn't think it would be a molt issue, and there aren't many feathers laying around.
So, I have six girls all up, no rooster. Also, I think Isa Browns are the same or similar to Golden Sex linked?? Or something similar.