We have a mallard couple that have nested on our property. In May, twelve ducklings hatched and within a day, the mother led them off the property to the woods. A few weeks later we noticed a male and female hanging around the same nesting area and when we looked there were more eggs in the nest. This time things are not going as smoothly. A lone duckling hatched four days ago and the mother continues to sit on the nest. We can see there are five eggs still in the nest. My question is this--Do you think the eggs are viable? If not, would the female continue to try to incubate eggs that may not be viable? Do ducks know the difference between viable and non-viable eggs? We are concerned about the health of the female.