Loud Quacking!

Does she have the company of other ducks? if so maybe she is loudly asking" Hey Ma where's the peas"

 

Oh, man... anytime they hear my voice the quacking goes wild.
I blame the peas.

As for why any duck quacks loudly out of the blue? Unless you speak duck I doubt you'll ever know. They just do that sometimes. They do alot of crazy stuff. Like occasionally sprinting across the yard like they're running from something for no reason at all.

 

Oh Lordy, it could ANYTHING. If one wanders away from the others, it will QUACK loudly. I usually just say, "Hey, turn around, they're RIGHT HERE!" Or they could be startled by something, chasing bugs, worms, grass, etc. They quack if they want let out (I put them inside their covered run if I am leaving the property.) As long as they have food, clean(ish) water and are healthy, then let them be ducks and quack. It's what they do.....quack.