I saw the two cockerels on left in first picture that Donarae saw. Note the blotchy white patches centered on wing and shoulders with little white elsewhere? That's the tell all on Silver birds and can be see as early as 5 weeks of age. Sure there are other markers but not as easy and accurate as the white shoulders. Not to mention you can't go by red combs as rose comb pullets can show red at early age.
