Sexing Jersey Black Giant chicks?

[cruizer]

I have 3, 2 week old chicks. Two are supposed to be pullets and 1 should be a male. The tail feathers are coming in on 2 of them and the 1 hasno tail feathers. Is tail feathers/no tail feathers a way to guess the sex?
I have 14 other pullets of different breeds and all of them are getting the tail feathers. Is the lone JBG chick with no tail feathers my male?

cruizer

 

[PotterWatch]

In general, roos take longer to get tail feathers than pullets. Doesn't always apply, but it is something to consider.

 

[Master S.M.C]

at four weeks roos have partial combs you can tell