Etymology

The word duck comes from Old English *dūce “diver”, a derivative of the verb *dūcan “to duck, bend down low as if to get under something, or dive”, because of the way many species in the dabbling duck group feed by upending; compare with Dutch duiken and German tauchen “to dive”.

This word replaced Old English ened/ænid “duck”, possibly to avoid confusion with other Old English words, like ende “end” with similar forms. Other Germanic languages still have similar words for “duck”, for example, Dutch eend “duck”, German Ente “duck” and Norwegian and “duck”. The word ened/ænid was inherited from Proto-Indo-European; compare: Latin anas “duck”, Lithuanian ántis “duck”, Ancient Greek nēssa/nētta (νῆσσα, νῆττα) “duck”, and Sanskrit ātí “water bird”, among others.

A duckling is a young duck in downy plumage^[1] or baby duck,^[2] but in the food trade a young domestic duck which has just reached adult size and bulk and its meat is still fully tender, is sometimes labelled as a duckling.

A male duck is called a drake and the female is called a duck, or in ornithology a hen.^[3][4]

Morphology

The overall body plan of ducks is elongated and broad, and the ducks are also relatively long-necked, albeit not as long-necked as the geese and swans. The body shape of diving ducks varies somewhat from this in being more rounded. The bill is usually broad and contains serrated pectens, which are particularly well defined in the filter-feeding species. In the case of some fishing species the bill is long and strongly serrated. The scaled legs are strong and well developed, and generally set far back on the body, more so in the highly aquatic species. The wings are very strong and are generally short and pointed, and the flight of ducks requires fast continuous strokes, requiring in turn strong wing muscles. Three species of steamer duck are almost flightless, however. Many species of duck are temporarily flightless while moulting; they seek out protected habitat with good food supplies during this period. This moult typically precedes migration.

The drakes of northern species often have extravagant plumage, but that is moulted in summer to give a more female-like appearance, the “eclipse” plumage. Southern resident species typically show less sexual dimorphism, although there are exceptions such as the paradise shelduck of New Zealand, which is both strikingly sexually dimorphic and in which the female’s plumage is brighter than that of the male. The plumage of juvenile birds generally resembles that of the female. Over the course of evolution, female ducks have evolved to have a corkscrew shaped vagina to prevent rape.

Behaviour

Feeding

Ducks eat a variety of food sources such as grasses, aquatic plants, fish, insects, small amphibians, worms, and small molluscs.

Dabbling ducks feed on the surface of water or on land, or as deep as they can reach by up-ending without completely submerging.^[5] Along the edge of the beak, there is a comb-like structure called a pecten. This strains the water squirting from the side of the beak and traps any food. The pecten is also used to preen feathers and to hold slippery food items.

Diving ducks and sea ducks forage deep underwater. To be able to submerge more easily, the diving ducks are heavier than dabbling ducks, and therefore have more difficulty taking off to fly.

A few specialized species such as the mergansers are adapted to catch and swallow large fish.

The others have the characteristic wide flat beak adapted to dredging-type jobs such as pulling up waterweed, pulling worms and small molluscs out of mud, searching for insect larvae, and bulk jobs such as dredging out, holding, turning head first, and swallowing a squirming frog. To avoid injury when digging into sediment it has no cere, but the nostrils come out through hard horn.

The Guardian (British newspaper) published an article advising that ducks should not be fed with bread because it damages the health of the ducks and pollutes waterways.^[6]

Breeding

Ducks generally only have one partner at a time, although the partnership usually only lasts one year.^[7] Larger species and the more sedentary species (like fast-river specialists) tend to have pair-bonds that last numerous years.^[8] Most duck species breed once a year, choosing to do so in favourable conditions (spring/summer or wet seasons). Ducks also tend to make a nest before breeding, and, after hatching, lead their ducklings to water. Mother ducks are very caring and protective of their young, but may abandon some of their ducklings if they are physically stuck in an area they cannot get out of (such as nesting in an enclosed courtyard) or are not prospering due to genetic defects or sickness brought about by hypothermia, starvation, or disease. Ducklings can also be orphaned by inconsistent late hatching where a few eggs hatch after the mother has abandoned the nest and led her ducklings to water.^[9]
Most domestic ducks neglect their eggs and ducklings, and their eggs must be hatched under a broody hen or artificially.

Communication

Female mallard ducks (as well as several other species in the genus Anas, such as the American and Pacific black ducks) make the classic “quack” sound while males make a similar but raspier sound that is sometimes written as “breeeeze”,^{[10][self-published source?]} but, despite widespread misconceptions, most species of duck do not “quack”.^[11] In general, ducks make a wide range of calls, ranging from whistles, cooing, yodels and grunts. For example, the scaup – which are diving ducks – make a noise like “scaup” (hence their name). Calls may be loud displaying calls or quieter contact calls.

A common urban legend claims that duck quacks do not echo; however, this has been proven to be false. This myth was first debunked by the Acoustics Research Centre at the University of Salford in 2003 as part of the British Association‘s Festival of Science.^[12] It was also debunked in one of the earlier episodes of the popular Discovery Channel television show MythBusters.^[13]

Distribution and habitat

The ducks have a cosmopolitan distribution. A number of species manage to live on sub-Antarctic islands like South Georgia and the Auckland Islands. Numerous ducks have managed to establish themselves on oceanic islands such as Hawaii, New Zealand and Kerguelen, although many of these species and populations are threatened or have become extinct.

Some duck species, mainly those breeding in the temperate and Arctic Northern Hemisphere, are migratory; those in the tropics, however, are generally not. Some ducks, particularly in Australia where rainfall is patchy and erratic, are nomadic, seeking out the temporary lakes and pools that form after localised heavy rain.^[14]

Predators

Worldwide, ducks have many predators. Ducklings are particularly vulnerable, since their inability to fly makes them easy prey not only for predatory birds but also for large fish like pike, crocodilians, predatory testudines such as the Alligator snapping turtle, and other aquatic hunters, including fish-eating birds such as herons. Ducks’ nests are raided by land-based predators, and brooding females may be caught unaware on the nest by mammals, such as foxes, or large birds, such as hawks or owls.

Adult ducks are fast fliers, but may be caught on the water by large aquatic predators including big fish such as the North American muskie and the European pike. In flight, ducks are safe from all but a few predators such as humans and the peregrine falcon, which regularly uses its speed and strength to catch ducks.

Relationship with humans

Domestication

Ducks have many economic uses, being farmed for their meat, eggs, and feathers (particularly their down). Approximately 3 billion ducks are slaughtered each year for meat worldwide.^[15] They are also kept and bred by aviculturists and often displayed in zoos. Almost all the varieties of domestic ducks are descended from the mallard (Anas platyrhynchos), apart from the Muscovy duck (Cairina moschata).^[16][17] The call duck is another example of a domestic duck breed. Its name comes from its original use established by hunters, as a decoy to attract wild mallards from the sky, into traps set for them on the ground. The call duck is the world’s smallest domestic duck breed, as it weighs less than 1 kg (2.2 lb).^[18]