How soon can partridge silkies be sexed?

[racuda]

I've only got one, hatched yesterday, so nothing to compare to. I know the whites and buffs will take a while, but can't partridges be sexed sooner?

 

[Sonoran Silkies]

You can usually tell when their wing feathers start growing in. The ones covered with penciling are females, those with only a bit of penciling are males.