i was thinking the same thing but as it turns out, most ducks will not have a second hatch after they have their first of the year. usually what tends to happen is that the skunks, coons and foxes will get into the eggs before they hatch and eat the eggs, if this happens before they hatch a hen mallard will renest and breed again. After the eggs hatch if the babies are preyed on then the hen will usually not renest. Hens will renest up to 5 or 6 times per year sometimes, so chances are she sucks at picking a spot for a nest or there are a lot of predators around that area, chances are both... there are an elevating amount of predators lately as less and less people are trapping. We need to get waterfowlers to understand what they can do for the ducks and themselves, get a trapping license and go trapping during the furbearer season after duck hunting is over, it will help everyone out.
Sorry, went off on a tangent. anyways, yea, chances are not a second hatch, but the first hatch after several attempts of nesting.