Thanks Kitannah..
I think I heard 'her' crowing this morning. I'm a bit annoyed as I was guarantted by the breeder that it was a large female silkie and it was vent sexed.
I've had breeders tell me all sorts of things when it comes to sexing chickens. None of the usual sexing techniques work with silkies. Don't worry I've also been ' bluffed ' by a breeders line of " I've been breeding chickens for 25 years ................... ". If you only recently purchased the roo I would contact the breeder and ask them to replace it. If you have reared it , then you have probably already formed an attachment to him.