That is a no-go for calls then! - My ducks are free ranging on IDontKnowHowManyAcres and i cannot cover all that with netting. And we have red-tail- and red-shouldered-hawks. The crows are standing guard though, but sometimes a hawk manages to sneak through and to scare the carp out of the ducks.Well..
For one thing, calls can fly. So that would give her an advantage over the bellybutton.
If you were serious about wanting them though, I would advise ya to make a covered run for them though to keep them safe when your not around. They're the perfect snack size for sky predators.