Feel the spacing between the pubic bones. Girls will have more space, and they will be somewhat flexible. Boys will be tight and close together--no need to push out an egg.
I have to disagree with everyone. All the birds show penciling consistent with being female; not to say tat there couldn't be a henny feathered boy in there, but at this age I would make no bets. Crests in pet quality birds tend to not match the round or fullness of show quality brds; usually...