As quackingdom said, it depends on the individuals, but the three females I started out with all went broody, and pretty much all at the same time! The eggs were unfertile though (the drake shot blanks) so I ended up having to shoo them off their nests after over a month (Muscovy take 35 days...
I shall await the posting of the picture tomorrow! Can't wait to see her, I love the blues (as you can tell by my avatar)
If you worry about her flying, you can clip her flight feathers. And yes, the trill is what made me fall in love with them. So sweet! In fact, one of my first Muscovy is...
I've found my females won't develop much caruncle growth until a bit later. Also, I have heard mine quack when stressed (such as being picked up) and I know mine are pure Muscovy. It's just very rare, they usually will just make their sweet little trills or hiss.
A picture would definitely...