What age can you successfully sex Silkies? With any certainty, when they either lay an egg or crow...which is about 4 to 6 months.
You can get some clues earlier, but there will always be that one, or two, that defy gender.
Boys tend to be lankier, taller, have a fuller pea comb, wattles, and an impressive mohawk.
Girls tend to be squattier, rounder, little to no pea comb or wattles, and have a round pom pom look.
But with identical feather coloring and shape, until some subtle saddle streamers finally show up (or not), you can't really rely on feathering to help.
Watch the combs and crests. That is *generally* the most reliable, but I'm sorry Silkies are notorious for fooling even the expert breeders. (But THEY know, and I'm sure are laughing.)
LofMc