Duck droppings are harmful if allowed to dry and harbor a mould that when ingested will cause long term illness. Mainly small children are at risk. The droppings in the pool will be sanitised by the pool chlorine however I would like to see the level of chlorine sanitiser at around 5ppm to be sure.
Also make sure to clean the filter often.
No.
If the result you want is a mallard, yes. If mallards can just breed with other ducks, yes, a mallard duck can breed other breed ducks.
Mallard ducks are not capable of changing gender. There is no known species of duck that is capable of that.
Mallard ducks were never introduced. Mallards were the first duck ever on planet Earth.
from an egg
Yes.
yes they do
Foxes, and raccoons eat young mallard ducks. Snapping turtles will also eat them. Mallard duck eggs are eaten by snakes, and crows.
A box of quackers
Yes, South Carolina has mallard ducks. These ducks can be found in almost any area with mild temperatures across Asia, Europe, and America.
a drake or mallard
yes they do