Birds
Mallard
Anas platyrhynchos · also called wild duck, mallard duck
The mallard is the default duck — the green-headed drake and mottled-brown hen of park ponds, farm dams, city rivers, and marshes across most of the world. It is also one of the most successful and adaptable birds alive, and the source of almost every domestic duck.
Overview
Mallards are found across the whole Northern Hemisphere and have been introduced widely beyond it. They use essentially any body of water — lakes, rivers, marshes, flooded fields, estuaries, urban ponds, ditches, and reservoirs — and tolerate people well, which is a large part of their success. Northern populations migrate; birds in mild regions stay put year-round. Outside the breeding season they gather in large flocks.
Feeding
The mallard is a dabbling duck. It feeds by tipping forward to graze plants and pick invertebrates off the bottom of shallow water, by skimming the surface, and by grazing on land — and it filters small food particles through fine lamellae along the edges of its broad bill. This generalist, flexible feeding lets mallards thrive on natural wetlands and on spilt grain, bread, and food waste alike.
Body and behaviour
Both sexes carry the iridescent blue speculum on the wing, edged with white, a reliable identification mark. Males in breeding condition have the glossy green head, yellow bill, white neck-ring, and chestnut breast; females are cryptically brown for nesting.
Mallards, like many birds, can sleep unihemispherically — resting one half of the brain while the other stays alert, with the corresponding eye open — which is especially useful for a bird at the edge of a sleeping flock, watching for predators.
Reproduction
Pairs form in autumn and winter. The female builds a down-lined nest on the ground, usually near water but sometimes surprisingly far from it, and lays around 8 to 13 eggs. The ducklings are precocial — they leave the nest within a day of hatching, following the hen to water and feeding themselves, though she guards and broods them for weeks. Drakes take no part in raising the young and moult into eclipse plumage while the female incubates.
Status
The mallard is Least Concern, abundant, and increasing across much of its range. Its very adaptability creates the one conservation issue attached to it: through introduction and range expansion, mallards hybridise with and genetically overwhelm several localised relatives, including the Hawaiian duck, New Zealand grey duck, and American black duck, eroding those species’ distinctiveness.
Mallard: common questions
Are all domestic ducks descended from mallards?
Nearly all — the main exception is the Muscovy duck, a separate species from South America. The Pekin, Rouen, Khaki Campbell, Indian Runner, call ducks, and the rest were all bred from the wild mallard, mostly in China and Europe over the last two to three thousand years, selected for size, egg-laying, or appearance. Because the two remain the same species, domestic and feral ducks interbreed readily with wild mallards.
What does it mean that a mallard is a "dabbling duck"?
Dabbling ducks feed at or just below the surface rather than diving. A mallard up-ends — tail in the air, head underwater — to reach plants and invertebrates on the bottom of shallow water, and it also skims the surface, straining tiny food items through rows of comb-like ridges (lamellae) along the edges of its bill, the same filtering principle a flamingo or a baleen whale uses. Their legs are set centrally so they walk well on land, unlike diving ducks.
Why do male mallards look drab in late summer?
After breeding, drakes moult all their flight feathers at once and cannot fly for three to four weeks — a dangerous, vulnerable period. During it they also swap their bright green head and chestnut breast for dull, mottled brown "eclipse" plumage that resembles a female's, providing camouflage while they are grounded. They moult back into breeding colours in autumn.
Is the mallard's success a conservation concern?
In places, yes. The mallard is so adaptable and so willing to hybridise that where it has been introduced or has spread into the range of a related duck, it can genetically swamp the local species. The Hawaiian duck, the New Zealand grey duck, the Florida mottled duck, and the American black duck have all been affected by interbreeding with mallards, blurring or threatening those distinct forms.