Question

Can a pair of black swan decoys intended to deter Canadian Geese, and placed in a community retention pond in Ohio, likely also deter Mallards from their familiar nesting/raising habitat?

Also, neighbors placed the black swan decoys because they want to keep the Canadian geese "poop" off all of the adjoining properties, sidewalks and streets.   

My concern is the Mallard population seems to be fleeing to one pond now. In some instances there are over 50 Mallards in one pond, which is a 40% increase over the past populations.
What about the excrement of those numbers?

I appreciate the sanctuary of birds/ducks in community retention ponds, but think the "fear factor" of the black swans is relocating the once-content Mallards which had been nesting among two - three Association retention ponds.   These ponds have very limited water flow.

Thank you.