Duck is the common name for a large number of species in the waterfowl family Anatidae, which also includes swans and geese. Ducks are divided among several subfamilies in the family Anatidae; they do not represent a monophyletic group (the group of all descendants of a single common ancestral species) but a form taxon, since swans and geese are not considered ducks. Ducks are mostly aquatic birds, mostly smaller than the swans and geese, and may be found in both fresh water and sea water.
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” and German Ente “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.
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 lamellae, 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 like the paradise shelduck of New Zealand which is both strikingly sexually dimorphic and where 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.
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. 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
Ducks are generally monogamous, although these bonds usually last only a single year. Larger species and the more sedentary species (like fast river specialists) tend to have pair-bonds that last numerous years. 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.
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