My silkies and showgirls are often hatched with both crest and beard. When I have a few in this room with me, I've had them (have one now) who start crowing at 18 days. The first of these I heard, I thought it was in distress, because it sounds like a strangled squeak. If they're not in the room with me, I don't hear this early crow until much, much later. After you've heard it once, it is unmistakeable.