Mallard

Name and taxonomy

Carl Linnaeus described the mallard in 1758 and gave it two names at once. Later writers preferred the second of those names for a long time. In 1906 Einar Lonnberg showed that Anas platyrhynchos came first in the book. That name has stood ever since. Anas is Latin for duck, and platyrhynchos is Greek for broad-billed.

The English word mallard once meant any wild drake. It came from Old French, and older English spellings include maudelard. Two subspecies are accepted today. Several ducks once ranked as mallard subspecies now stand as species. Those include the Hawaiian duck, the mottled duck and the American black duck. Researchers sequenced the mallard genome in 2013.

Evolution and relatives

Mitochondrial evidence suggests the mallard arose somewhere around Siberia. Its bones appear suddenly in European deposits, with no clear local ancestor. A large Ice Age form has its own palaeosubspecies name. American and Eurasian birds differ in mitochondrial DNA. The nuclear genome, by contrast, shows very little structure across the range.

The mallard crosses with other ducks more readily than almost any bird. Wild crosses are known with more than 40 other species. A further 20 species have produced crosses with it in captivity. Fertile hybrids usually have two parents from the genus Anas. Aleutian birds show limited gene flow and may be turning into a subspecies.

Appearance

The bird is 50 to 65 cm long, and the body makes up about two thirds of that. The wings span 81 to 98 cm and the bill runs 4.4 to 6.1 cm. Weight falls between 0.7 and 1.6 kg. A breeding drake has a glossy green head above a clean white ring. His breast is brown with a purple cast, and his rear is black. His bill is yellow-orange with a black tip.

The female is buff and dark brown on every feather, with a darker crown. Her bill runs from dark to a mottled orange. Both sexes carry a purple-blue speculum edged in white on the wing. The speculum is shed for a short period during the summer moult. A drake in summer eclipse plumage probably looks much like a female to a predator. A duckling is yellow below and black above, with black legs and bill.

The species illustrates two classic rules of body shape in animals. Greenland mallards are larger than birds from further south. Their bills are also smaller, which loses less heat. Sex reversal happens now and then, so a female can grow male plumage. Domestic birds add white and many other colours to the range.

Habitat and range

The mallard breeds from Alaska to Mexico and from Iceland to Japan. Introduced flocks now live in Australia, New Zealand and southern South America. GBIF holds records from 194 countries, more than for almost any bird. Northern breeders migrate, and southern ones often stay put. North American birds winter as far as the southern states and northern Mexico.

Habitat runs from Arctic tundra to the subtropics. Fresh water is preferred, but estuaries and sheltered coast are used too. The birds keep to water under about 0.9 metres deep. Anything more than a few metres deep is usually avoided. Plants in the water appear to matter more than the size of the water body. Park lakes, farm ponds and drainage ditches all hold mallards.

Diet and feeding

The mallard eats plants and animals and switches between them freely. Seeds, roots, tubers, stems and grain form the plant half. Snails, insects, worms and small crustaceans form the animal half. The balance shifts with the season and with the bird's own state. A laying female takes far more animal food than a male does.

Dabbling is the usual method: the bird tips forward and sifts the shallows. It also dips its head and neck, or grazes on land for seeds and roots. Ducklings live mainly on water insects in their first weeks. Frogs, tadpoles and small fish are taken when the chance comes. In 2017 a flock in Romania was seen killing and eating small migrant birds. That was the first record of mallards taking prey of that size.

Behaviour and social life

Outside the breeding season mallards gather in flocks, which are called sords. Flocks often mix with other duck species on the same water. Pairs form in autumn, well before any nesting. The drake leaves once the female starts to lay. Males then gather together and wait for the summer moult.

Both sexes turn aggressive in the breeding season. Drakes fight by pecking hard at a rival's chest. Unpaired drakes chase and force themselves on isolated females. The target is sometimes a female of another species entirely. Mallards were the first birds shown to sleep with one eye open. Half the brain rests while the other half watches, which probably guards the flock edge.

Mallards use city water as readily as wild marsh. Park birds learn to approach people and to expect food. That tameness probably explains why the species is so familiar. Wild flocks away from towns appear to stay far more cautious. The same species may therefore behave in two quite different ways.

Communication and senses

The famous quack belongs to the female. She gives 2 to 10 quacks in a run, starting loud and fading away. That call carries a long distance and gathers other ducks to her. The drake makes a similar sound, but deeper and much quieter.

A sitting female uses a shortened call that her ducklings answer. The rhythm of those quacks teaches a duckling which species it belongs to. She hisses if anything comes near the nest or the brood. Taking off, the wings make a faint whistle. A study of two English populations found louder calls in London than in Cornwall. The researchers described the difference as a regional accent.

Reproduction and life cycle

The female chooses the nest site and builds it alone. Most nests sit on the ground in thick cover, where her plumage hides her. Some are far stranger: tree hollows, boathouses, roof gardens and balconies. A high nest probably leaves the ducklings a hard journey to water. She lays 8 to 13 pale eggs, one on each alternate day.

Each egg is about 58 millimetres long and 32 mm wide. Incubation starts only when the clutch is nearly complete. It lasts 27 to 28 days, and she does all of it. Ducklings swim from the day they hatch and feed themselves at once. They still follow their mother closely, which teaches them where food is. A female normally attacks stray ducklings rather than adopting them.

The young fly 50 to 60 days after hatching. A male's bill turns yellow and his central tail feather curls. Full adult plumage arrives between six and ten months. A mallard is adult at about fourteen months old. Average life is only about 3 years, though a bird can reach 20. Other ducks sometimes lay eggs in a mallard nest and leave her to raise them.

Predators and threats

Ducklings and sitting females are probably the easiest targets. The red fox takes more adults than any other predator does. North American adults are hunted by at least 15 different raptor species. That list runs from harriers and short-eared owls to bald and golden eagles. Mink, raccoons, skunks, snakes and domestic cats and dogs take their share.

Water holds its own hunters. Herons, large gulls, pike and wels catfish all kill ducks or ducklings. Mute swans drive mallards off and sometimes kill them near a swan brood. Hot summers with low water raise the risk of botulism. A botulism outbreak can kill mallards in very large numbers. Loss of wetland is the underlying threat, and hunting removes millions a year.

Population and conservation

The IUCN has rated the mallard as Least Concern since 1998. The range covers more than 65 million square kilometres. More than 17 million mature birds were estimated for the most recent assessment. That very large total is nonetheless falling. Naturalists have logged 953,027 mallard sightings on iNaturalist.

The species is treated as invasive in several countries. Released and feral birds breed with local ducks and produce fertile young. Over time the two gene pools merge and the rarer duck disappears. The mallard can cross with 63 other species, which makes the risk broad. Florida bans private ownership of mallards to protect the mottled duck. New Zealand and Australia list the bird as invasive beside the Pacific black duck.

Relationship with humans

Nearly every domestic duck breed descends from the mallard. Genetic work points to one domestication in southern China, around 2000 BC. Selection then split the stock into meat lines and egg lines. The White Pekin is the main meat breed, and the Indian Runner lays over 300 eggs a year. China now produces over 80% of the world's ducks.

Rice farmers in East and Southeast Asia put ducks into the paddy. The birds eat pests, stir the soil and fertilise the crop at the same time. Wild mallards have been eaten since the Neolithic, with evidence from Greece. The bird is among the most shot waterfowl anywhere, and licence money funds wetland work.

Mallards also collide with aircraft. American records list 1320 mallard strikes since standardised collection began. Of those, 261 damaged the aircraft. One bird was hit at a cruising height of 6,400 metres. Tests show that mallards fail to get out of the way of fast vehicles.

In culture and myth

Artists in several old civilisations drew the duck as a sign of fertility. The mallard is probably the wild bird behind that image in Europe and Asia. Its shape appears on decoys, weathervanes and pub signs across the north. The green head appears to be one of the most copied patterns in bird art.

Children's books are full of ducks that seem to be mallards in all but name. Beatrix Potter published The Tale of Jemima Puddle-Duck in 1908. Prokofiev gave the duck an oboe in Peter and the Wolf in 1936. Robert McCloskey set Make Way for Ducklings on a pair of mallards in Boston. An animated film of recent years followed a mallard family from New England.

One real bird became famous on its own. A drake turned up on the Pacific island of Niue in 2018, far outside the range. Islanders named him Trevor and treated him as a local celebrity. He died there the following year. The story probably says as much about people as about ducks.