Mallards prefer calm, shallow sanctuaries, but can be found in almost any body of freshwater across Asia, Europe, and North America. They’re also found in saltwater and brackish water and are commonly found in wetlands. The male, or drake, is the more distinctively colored of the mallards. Its iconic green head sits atop a white neckband that sets off a chestnut-colored chest and gray body. Females are mottled drab brown in color, but sport iridescent purple-blue wing feathers that are visible as a patch on their sides. They grow to about 26 inches (65 centimeters) in length and can weigh up to 3 pounds (1.4 kilograms).
Mallard groups can often be seen head dipping or completely upending in the water. They rarely dive though, spending their time near the surface and dabbling for invertebrates, fish, amphibians, and a variety of plants. They also graze on land, feeding on grains and plants.
Mated pairs migrate to and breed in the northern parts of their range and build nests on the ground or in a protected cavity. They normally lay about a dozen eggs, and the incubation period lasts just under a month. Mallards are territorial during much of this period, but once incubation is well underway, males abandon the nest and join a flock of other males. Most mallard species are common and not considered threatened. However one threat to their populations includes hybridization with other ducks.
The mallard is omnivorous and very flexible in its foods choice. Its diet may vary based on several factors, including the stage of the breeding cycle, short-term variations in available food, nutrientavailability, and inter and intraspecific competition. The majority of the mallard's diet seems to be made up of gastropods, invertebrates (including beetles, flies, lepidopterans, dragonflies, and caddisflies), crustaceans, worms, many varieties of seeds and plant matter, and roots and tubers. During the breeding season, male birds were recorded to have eaten 37.6% animal matter and 62.4% plant matter, most notably Echinochloa crus-galli, and nonlaying females ate 37.0% animal matter and 63.0% plant matter, while laying females ate 71.9% animal matter and only 28.1% plant matter. Plants generally make up a larger part of the bird's diet, especially during autumn migration and in the winter.
Mallards usually form pairs (in October and November in the Northern hemisphere) only until the female lays eggs at the start of nesting season which is around the beginning of spring, at which time she is left by the male who joins up with other males to await the moulting period which begins in June (in the Northern hemisphere). During the brief time before this, however, the males are still sexually potent and some of them either remain on standby to sire replacement clutches (for female mallards that have lost or abandoned their previous clutch) or forcibly mate with females that appear to be isolated or unattached regardless of their species and whether or not they have a brood of ducklings.
The nesting period can be very stressful for the female since she lays more than half her body weight in eggs. She requires a lot of rest and a feeding/loafing area that is safe from predators. When seeking out a suitable nesting site, the female's preferences are areas that are well concealed, inaccessible to ground predators, or have few predators nearby. This can include nesting sites in urban areas such as roof gardens, enclosed courtyards, and flower boxes on window ledges and balconies more than one story up, which the ducklings cannot leave safely without human intervention. The clutch is 8–13 eggs, which are incubated for 27–28 days to hatching with 50–60 days to fledgling. The ducklings are precocial and fully capable of swimming as soon as they hatch. However, filial imprinting compels them to instinctively stay near the mother not only for warmth and protection but also to learn about and remember their habitat as well as how and where to forage for food. When ducklings mature into flight-capable juveniles, they learn about and remember their traditional migratory routes (unless they are born and raised in captivity). After this, the juveniles and the mother may either part or remain together until the breeding season arrives.
During the breeding season, both male and female mallards can become aggressive, driving off competitors to themselves or their mate by charging at them. Males tend to fight more than females, and attack each other by repeatedly pecking at their rival's chest, ripping out feathers and even skin on rare occasions.
When they pair off with mating partners, often one or several drakes end up left out. This group sometimes targets an isolated female duck, even one of a different species, and proceeds to chase and peck at her until she weakens, at which point the males take turns copulating with the female. Lebret (1961) calls this behavior "Attempted Rape Flight" and Cramp & Simmons (1977) speak of "rape-intent flights". Male mallards also occasionally chase other male ducks of a different species, and even each other, in the same way. In one documented case of "homosexual necrophilia", a male mallard copulated with another male he was chasing after the chased male died upon flying into a glass window. This paper was awarded with an Ig Nobel Prize in 2003.
Mallards are opportunistically targeted by brood parasites, occasionally having eggs laid in their nests by Redheads, ruddy ducks, lesser scaup, gadwalls, northern shovelers, northern pintails, cinnamon teal, common goldeneyes, and other mallards. These eggs are generally accepted when they resemble the eggs of the host mallard, although the hen may attempt to eject them or even abandon the nest if parasitism occurs during egg laying. Mallards of all ages (but especially young ones) and in all locations must contend with a wide diversity of predators including raptors, mustelids, corvids, snakes, raccoons, opossums, skunks, turtles, large fish and felids and canids, including domesticated ones. The most prolific natural predators of adult mallards are red foxes(which most often pick off brooding females) and the faster or larger birds of prey, i.e. peregrine falcons, Aquila eagles or Haliaeetus eagles. In North America, adult mallards face no fewer than 15 species of birds of prey, from hen harriers and short-eared owls (both smaller than a mallard) to huge bald and golden eagles, and about a dozen species of mammalian predator, not counting several more avian and mammalian predators who threaten eggs and nestlings.
Mallards are also preyed upon by other waterside apex predators, such as the Grey heron (Ardea cinerea), European herring gull (Larus argentatus) and the pike (Esox lucius). Crows (Corvus sp.) are also known to kill ducklings and adults on occasion.