wing feather length determining gender

[happymorrows]

I have read elsewhere on the forum that if the wing feathers are shorter it is probably a roo. I have a "mystery chick" that I got from McMurray. It's feathers look a lot like my barred rocks at this point and they are about 3 weeks old. The big difference between this one and my others is that the wing feathers are a lot shorter. Is this a breed or a gender distinction?

 

[silkiechicken]

Search "feather sexing". It is a slow feathering male of any breed bred against fast feathering females to get chicks with differing primary feather lengths in the babies.