Ducks do lay eggs. Eggs laid together in one batch are referred to as a "clutch." Female ducks lay anywhere from eight to 16 eggs in a clutch, with nine being the average.
A female duck spends a great deal of time incubating the eggs once they are laid. She only leaves for short periods of time. The female duck rotates and shifts the eggs in the nest so that the heat from her body warms them evenly. Her body heat ensures that the eggs hatch. Outside factors such as weather, the female's age, the eggs' condition and size, and the risk of predators help determine how long the incubation period is for each clutch.