week older rooster sparring?

I have 2 chicks that hatched one week ago today. I was sure both of them were females. The Welsummer is a chipmunk color, gorgeous head color and markings (the males are silvery at birth?) and a black penguin looking cuckoo marans. He? was introduced to a couple of pairs of older chicks, couple months old and he charged right up to all of them one at a time and got chest to chest. They of course are giants compared to him. The Welusmmer chick was like, oh, another one, whatever, I'm going back to exploring the crumbs in the rug and went about her business. Does this behavior indicate the black chick is a boy?

 

okay, so can't sex that way...argh, i just have to know!
it is SO SO cute to watch that. I love that they found a cracker crumb in the carpet and played tackle fighting over it.