We may have been mistaken about Penny's "crowing". I finally heard her make the noise firsthand. It sounds like a loud, rusty door hinge. My wife assures me that that's the "crow". I think Penny is trying to mother the flock as well as affirm her place at the head of the peck order.
We bought a dog pen with a lid to exercise them outside. If Penny sees or hears a possible threat, she makes a sound similar to the happy trill, only rougher. It sounds something like a purr. They will then all freeze! It's pretty fascinating to watch. When she feels the threat is past, she makes a sound sort of like a soft, "chuck-chuck". Then they all go about their business.
If anyone doesn't listen, she will charge and knock her over or give her a peck.
The silkies constantly try getting under the standards' wings. Dominique will peck them or fly off; Penny tolerates it even though they're much too large to actually fit there.
She seems to have assumed responsibility for the flock's safety, and knows instinctively what to do. The loud rusty hinge noise seems to mean, "I'm your boss.... LISTEN to me!"