Calcium chloride has twice as much chloride as it does calcium. That may not be good for ducks or chickens, I'm not sure. There is also potassium chloride in it and what looks to be magnesium chloride which adds to the chloride count. There is alot of chloride in that product.
I don't know the dosage but each eggshell requires about 2 grams of calcium. That product has about 4 grams calcium per fl oz. I would guess and say start off with 1/4 oz daily and see if it helps.
Vitamin D helps with the absorption of calcium so you may try that with calcium.