Female Duck Does Not Sit on Eggs All of the Time?

Usually birds, all kinds, lay an egg a day or say every other day. But they don't usually sit or brood, till they have laid enough, 12 certainly seems like a large enough number. Questions come to mind 1. does she have privacy, somewhere other animals and humans won't disturb her. 2. Are male and female of same age 3. How often is a human checking on things? If they don't feel safe they won't always brood. 4. Was she raised by mother or incubated, sometimes they just don't know how. 5. Do you know how to candle an egg?

If she is tame and used to you, discard eggs, see if she starts laying again. If she does take a marker and date eggs as she lays them. If she's pretty tame this shouldn't bother her. After marking date, you can candle the eggs to see if a chick is growing. If you decide to take current eggs from her, crack a few and see if they've actually been fertilized by the male. Have you seen him mount her? Best advice I have is to get a library book, to help with some of these questions.