I got my three Australorps at the end of April this year, and I'm guessing they were around 18 weeks old at the time. They were black all over - with the rust tint on the chest, and the green sheen on the other feathers. Yesterday I saw a very noticeable WHTE wingtip on one of the girls! I'm out there with them daily, and can't understand how I missed this very obvious bit of white for over two months now. Can it just suddenly appear like that? Perhaps the feather in question was previously hidden behind the others? In case it's relevant, it's Penny, who has only just this week started laying.