With the most widespread breeding range of any duck in North America, the Mallard is not hard to find. Chances are that group you saw crossing the street or highway was, indeed, a Mallard brood. The Mallard's breeding range includes most of North America and parts of Mexico, Europe and Asia, and has been introduced to Australia.

Pair bonding in Mallards can begin as early as August and continues until January, although some females will remain un-paired until they reach the breeding grounds. Several males will surround a female and perform courtship rituals such as shaking their bodies as they swim alongside her. Once a female is impressed, she will follow her chosen male and perform her inciting behaviour, involving ritualized head movements and characteristic calls. Looks are important; females often choose for good plumage and courtship quality, which, like most things, improve with age. While many pair copulations are initiated by mutual head-pumping, Mallards are also known for having a high number of forced-pair copulations, where a paired male will copulate with another female without the head-pumping initiation, often leading to a brood of mixed paternity.

The male will follow the female as she searches for a nesting site, which can be up to several hundred meters away from the water's edge. Mallards typically choose to nest in dense grass, low shrubs or emergent wetland vegetation; however, they will also nest in odd areas such as magpie nests, under machinery and in hay-bales. Nests are usually constructed from surrounding litter (e.g., leaves twigs, grass). Once the female begins to lay her clutch, usually one egg per day until the clutch is complete (average of 9 eggs), she will cover the eggs with vegetation as well as breast and down feathers for warmth and to conceal them from predators while she is not attending the nest. Although the female increases time spent on the nest as the number of eggs increases, true incubation does not begin until the clutch is complete. If a Mallard hen's nest is destroyed, she will often re-nest, although she will likely lay fewer eggs because of depleted energy reserves. Once her ducklings have hatched and dried, the Mallard hen leads them to water to be reared; if the temperature is still cool, she may still brood the ducklings at night until they can maintain their own body temperatures; usually two weeks after hatch. Most males will leave when incubation begins, typically moving to large ponds where they will begin to molt into their eclipse plumage. During this phase they become virtually identical to the drab female; only the yellowish-green bill identifies his sex. The males will remain this way until fall, when they will return to their breeding plumage in preparation for fall migration and another breeding season. Females will typically remain with their young until they can fly, often undergoing their molt while rearing their brood.