There are several ways a male mallard (drake) courts a female (hen). One way is in the air. Several drakes may pursue a hen by flying high up in the air, circling, quacking loudly and flying rapidly. The hen will fly up to the drake of her choice, tap him with her bill and the two will fly off together as mates.
There are two types of classic swimming displays of courtship. In the first type, the drake swims restlessly behind or beside a hen and begins bobbing his beak up and down in the water. The hen will ignore him initially, while he continues to furtively jerk his bill up and down. Eventually, she will turn to him and begin to bob her bill up and down. They then bow to each other, establishing themselves as mates.
In the second type of swimming display of courtship, several drakes, with necks drawn back, will swim around one hen. After some time, each will suddenly place the tip of his bill in the water, stand up in the water, and quickly pass his bill over his breast in a jerk-like manner, emitting a tiny jet of water from the bill. At the same time, the drake will emit a low groaning sort of sound. Then, the tails are raised into the air two or three times quickly. All of these actions may be repeated several times. Finally, the head feathers puff up and the drake throws up his head and tail, stretches his neck out over the water, and swims rapidly around in all directions. All the drakes will then reconvene and repeat the process over again until one is selected by the hen.
Often mallards are paired before they migrate north in the spring. Copulation usually takes place in the water. Mallard pairs are generally monogamous although sometimes a paired male will pursue an extra-pair copulation. In this case, the forced copulation will have no courtship display.
Migrating flocks will break up into pairs and search for nesting sites. The female chooses the nesting site, often near where she was hatched. The nest is built entirely by the female, near water, with plenty of grass and shrubs for cover. It is the female who incubates and raises the ducklings alone. The males lose their bright plumage after breeding season and grow a basic plumage. While this is happening, they cannot fly, usually for a period of 10 days during incubation. After this period, when they can resume flying, the males abandon the females.