Mallards primarily nest around freshwater lakes, ponds, marshes and reservoirs across Pennsylvania, but it's not uncommon to find them nesting in agricultural fields and in residential areas. The hen typically nests within 100 yards of water, on the ground in a depression lined with reeds and grasses, with soft down added from her breast. She conceals the nest in tall grass, dead reeds, alfalfa or clover. A few individuals nest in stumps, tree cavities or in the crotches of trees. Eggs, from six to 15 but usually 8 to 12, are laid one per day.
Shells are smooth, light greenish or grayish buff, sometimes nearly white.
A hen occasionally will lay eggs in the nests of other ducks. Incubation takes 23-29 days. Within about 12 hours of their hatching, the hen leads her young to water. Mallards normally raise one brood a year, but if a skunk, crow, raccoon, opossum or other predator destroys her first clutch, a hen may try again. Nests are also lost to plowing, hayfield mowing and flooding.