Otters are carnivorous mammals in the subfamily Lutrinae. The 13 extant otter species are all semiaquatic, aquatic or marine, with diets based on fish and invertebrates. Lutrinae is a branch of the weasel family Mustelidae, which includes badgers, honey badgers, minks and wolverines; the word otter derives from the Old English word oter. This, cognate words in other Indo-European languages stem from the Proto-Indo-European language root *wódr̥, which gave rise to the English word "water". An otter's den is called a couch. Male otters are called dogs or boars, females are called bitches or sows, their offspring are called pups; the collective nouns for otters are bevy, lodge, romp or, when in water, raft. The feces of otters are identified by their distinctive aroma, the smell of, described as ranging from freshly mown hay to putrefied fish; the gestation period in otters is about 60 to 86 days. The newborn pup is cared for by the bitch and older offspring. Bitch otters reach sexual maturity at two years of age and males at three years.
The holt is built under a rocky cairn, more common in Scotland. It is lined with moss and grass. After one month, the pup can leave the holt and after two months, it is able to swim; the pup lives with its family for one year. Otters live up to 16 years, its usual source of food is fish, further downriver, but it may sample frogs and birds. Otters have long, slim bodies and short limbs, their most striking anatomical features are the powerful webbed feet used to swim, their seal-like abilities holding breath underwater. Most have sharp claws on their feet and all except the sea otter have long, muscular tails; the 13 species range in adult size from 0.6 to 1 to 45 kg in weight. The Asian small-clawed otter is the smallest otter species and the giant otter and sea otter are the largest, they have soft, insulated underfur, protected by an outer layer of long guard hairs. This traps a layer of air which keeps them dry and somewhat buoyant under water. Several otter species have high metabolic rates to help keep them warm.
European otters must eat 15% of their body weight each day, sea otters 20 to 25%, depending on the temperature. In water as warm as 10 °C, an otter needs to catch 100 g of fish per hour to survive. Most species hunt for three to nursing mothers up to eight hours each day. For most otters, fish is the staple of their diet; this is supplemented by frogs and crabs. Some otters are experts at opening shellfish, others will feed on available small mammals or birds. Prey-dependence leaves otters vulnerable to prey depletion. Sea otters are hunters of sea urchins and other shelled creatures, they are notable for their ability to use stones to break open shellfish on their stomachs. This skill must be learned by the young. Otters are active hunters, chasing prey in the water or searching the beds of rivers, lakes or the seas. Most species live beside water, but river otters enter it only to hunt or travel, otherwise spending much of their time on land to prevent their fur becoming waterlogged. Sea otters are more aquatic and live in the ocean for most of their lives.
Otters are playful animals and appear to engage in various behaviors for sheer enjoyment, such as making waterslides and sliding on them into the water. They may find and play with small stones. Different species vary in their social structure, with some being solitary, while others live in groups – in a few species these groups may be large. Genus Lutra Eurasian otter Hairy-nosed otter Japanese otter† Lutra euxena† Lutra castiglionis† Lutra simplicidens† Lutra trinacriae†Genus Hydrictis Spotted-necked otter Genus Lutrogale Smooth-coated otter Lutrogale robusta†Genus Lontra North American river otter Southern river otter Neotropical river otter Marine otter Genus Pteronura Giant otter Genus Amblonyx Asian small-clawed otter Genus Aonyx African clawless otter Genus Enhydra Sea otter Enhydra reevei†Genus †Megalenhydris Genus †Sardolutra Genus †Algarolutra Genus †Cyrnaonyx Genus †Teruelictis Genus †Enhydriodon Genus †Enhydritherium Genus †Teruelictis Genus †Limnonyx Genus †Lutravus Genus †Sivaonyx Genus †Torolutra Genus †Tyrrhenolutra Genus †Vishnuonyx Genus †Siamogale The European otter called the Eurasian otter, inhabits Europe, most of Asia and parts of North Africa.
In the British Isles, they were common as as the 1950s, but became rare in many areas due to the use of chlorinated hydrocarbon pesticides, habitat loss and water pollution. Population levels are now recovering strongly; the UK Biodiversity Action Plan envisages the re-establishment of otters by 2010 in all the UK rivers and coastal areas they inhabited in 1960. Roadkill deaths have become one of the significant threats to the success of their re-establishment; the North American river otter became one of the major animals hunted and trapped for fur in North America after European contact. River otters eat a variety of fish and shellfish, as well as birds. They
A leat is the name, common in the south and west of England and in Wales, for an artificial watercourse or aqueduct dug into the ground one supplying water to a watermill or its mill pond. Other common uses for leats include delivery of water for mineral washing and concentration, for irrigation, to serve a dye works or other industrial plant, provision of drinking water to a farm or household or as a catchment cut-off to improve the yield of a reservoir. According to the Oxford English Dictionary, leat is cognate with let in the sense of "allow to pass through". Other names for the same thing include fleam. In parts of northern England, for example around Sheffield, the equivalent word is goit. In southern England, a leat used to supply water for water-meadow irrigation is called a carrier, top carrier, or main. Leats start some distance above the mill or other destination, where an offtake or sluice gate diverts a proportion of the water from a river or stream. A weir in the source stream serves to provide a reservoir of water adequate for diversion.
The leat runs along the edge or side of the valley, at a shallower slope than the main stream. The gradient determines the flow rate together with the quality of the wetted surface of the leat; the flow rate may be calculated using the Manning formula. By the time it arrives at the water mill the difference in levels between the leat and the main stream is great enough to provide a useful head of water – several metres for a watermill, or a metre or less for the controlled irrigation of a water-meadow. Leats are used to increase the yield of a reservoir by trapping streams in nearby catchments by means of a contour leat; this transports it along the contour to the reservoir. Such leats are common around reservoirs in the uplands of Wales. Leats were built to work lead and silver ores in mining areas of Wales, Devon, the Pennines and the Leadhills/Wanlockhead area of Southern Scotland from the 17th century onwards, they were used to supply water for washing ore and powering mills. Leats were used extensively by the Romans, can still be seen at many sites, such as the Dolaucothi goldmines.
They used the aqueducts to prospect for ores by sluicing away the overburden of soil to reveal the bedrock in a method known as hushing. They could attack the ore veins by fire-setting, quench with water from a tank above the workings, remove the debris with waves of water, a method still used in hydraulic mining; the water supply could be used for washing the ore after crushing by simple machines driven by water. The Romans used them for supplying water to the bath-houses or thermae and to drive vertical water-wheels. There are many leats on Dartmoor constructed to provide power for mining activities, although some were sources of drinking water; the courses of many Dartmoor leats may still be followed. Many such leats on the moor are marked on the 1⁄50000 and 1⁄25000 Ordnance Survey maps, such as that serving the now-defunct Vitifer mine near the Warren House Inn. Drake's Leat, constructed in 1591 under the management of Sir Francis Drake, as an agent of the Corporation of Plymouth, to carry water from Dartmoor to Plymouth.
Devonport Leat constructed in the late 18th century to carry water to the expanding naval dockyard at Devonport. Acequia Aqueduct Flume Kunstgraben Roman aqueduct Roman engineering Roman mining
A footbridge is a bridge designed for pedestrians. While the primary meaning for a bridge is a structure which links "two points at a height above the ground", a footbridge can be a lower structure, such as a boardwalk, that enables pedestrians to cross wet, fragile, or mashy land. Bridges range from stepping stones–possibly the earliest man-made structure to "bridge" water–to elaborate steel structures. Another early bridge would have been a fallen tree. In some cases a footbridge can be both functional and a beautiful work of art. For rural communities in the developing world, a footbridge may be a community's only access to medical clinics, schools and markets. Simple suspension bridge designs have been developed to be sustainable and constructed in such areas using only local materials and labor. An enclosed footbridge between two buildings is sometimes known as a skyway. Bridges providing for both pedestrians and cyclists are referred to as greenbridges and form an important part of a sustainable transport system.
Footbridges are situated to allow pedestrians to cross water or railways in areas where there are no nearby roads. They are located across roads to let pedestrians cross safely without slowing traffic; the latter is a type of pedestrian separation structure, examples of which are found near schools. The simplest type of a bridge is stepping stones, so this may have been one of the earliest types of footbridge. Neolithic people built a form of a boardwalk across marshes, of which the Sweet Track, the Post Track are examples from England, that are around 6000 years old. Undoubtedly ancient peoples would have used log bridges; some of the first man-made bridges with significant span were intentionally felled trees. Among the oldest timber bridges is the Holzbrücke Rapperswil-Hurden crossing upper Lake Zürich in Switzerland. C; the first wooden footbridge led across Lake Zürich, followed by several reconstructions at least until the late 2nd century AD, when the Roman Empire built a 6-metre-wide wooden bridge.
Between 1358 and 1360, Rudolf IV, Duke of Austria, built a'new' wooden bridge across the lake, used to 1878 – measuring 1,450 metres in length and 4 metres wide. On April 6, 2001, the reconstructed wooden footbridge was opened, being the longest wooden bridge in Switzerland. A clapper bridge is an ancient form of bridge found on the moors of Devon and in other upland areas of the United Kingdom including Snowdonia and Anglesey, Cumbria and Lancashire, it is formed by large flat slabs of stone granite or schist, supported on stone piers, or resting on the banks of streams. Although credited with prehistoric origin, most were erected in medieval times, some in centuries. A famous example is found in the village of Postbridge. First recorded in the 14th century, the bridge is believed to have been built in the 13th century to enable pack horses to cross the river. Nowadays clapper bridges are only used as footbridges; the Kapellbrücke is a 204-metre-long footbridge crossing the River Reuss in the city of Lucerne in Switzerland.
It is the oldest wooden covered bridge in Europe, one of Switzerland's main tourist attractions. The bridge was built c. 1365 as part of Lucerne's fortifications. An early example of a skyway is the Vasari Corridor, an elevated, enclosed passageway in Florence, central Italy, which connects the Palazzo Vecchio with the Palazzo Pitti. Beginning on the south side of the Palazzo Vecchio, it joins the Uffizi Gallery and leaves on its south side, crossing the Lungarno dei Archibusieri and following the north bank of the River Arno until it crosses the river at Ponte Vecchio, it was built in five months by order of Duke Cosimo I de' Medici in 1565, to the design of Giorgio Vasari. Bank Bridge is a famous 25 metre long pedestrian bridge crossing the Griboedov Canal in Saint Petersburg, Russia. Like other bridges across the canal, the existing structure dates from 1826; the special popularity of the bridge was gained through angular sculptures of four winged lions crowning the abutments. They were designed by sculptor Pavel Sokolov, who contributed lions for Bridge of Lions.
Design of footbridges follows the same principles as for other bridges. However, because they are significantly lighter than vehicular bridges, they are more vulnerable to vibration and therefore dynamics effects are given more attention in design. International attention has been drawn to this issue in recent years by problems on the Pont de Solférino in Paris and the Millennium Bridge in London. To ensure footbridges are accessible to disabled and other mobility-impaired people, careful consideration is nowadays given to provision of access lifts or ramps, as required by relevant legislation; some old bridges in Venice are now equipped with a stairlift so that residents with a disability can cross them. Types of footbridges include: Beam Bridge Boardwalk Clapper bridge Duckboards, Timber trackway, Plank road, Corduroy road Moon bridge Simple suspension bridge Simple truss Stepping stones Zig-zag bridgeThe residential-scale footbridges all span a short distance and can be used for a broad range of applications.
Complicated engineering is not needed and the footbridges are built with available materials and basic tools. Different types of design footbridges incl
The Oxford University Parks referred to locally as the University Parks, the Uni Parks or just The Parks, is a large parkland area northeast of the city centre in Oxford, England. The park is bounded to the east by the River Cherwell, though a small plot of land called Mesopotamia sits between the upper and lower levels of the river. To the north of the parks is Norham Gardens and Lady Margaret Hall, to the west the Parks Road, the Science Area on South Parks Road to the south; the park is open to the public during the day, has gardens, large sports fields, exotic plants. It includes a cricket ground used by Oxford University Cricket Club. Part of the land on which the Parks is located had been used for recreation for a long time, it formed part of the University Walks said to have been used by Charles II to walk his dog in 1685; the land belonged to Merton College, in 1853/1854, the University of Oxford purchased 20 acres from Merton College to build the parks. Over an eleven-year period a total of 91 acres of land was acquired.
A portion of this land was set aside for the University Museum, built between 1855 and 1860. Between 1912 and early 1950s, a further portion was used to build the Science Area, so the current site measures around 74 acres; the Parks was laid out in 1864, the work supervised by William Baxter, appointed the first superintendent of the parks in 1866. Parts of the Parks were designated to be used for recreational purposes. 25 acres of the land had been set aside as the University Cricket Grounds, the cricket pavilion was built in 1881. The Parks is used for other sports such as rugby football, lacrosse and croquet; the rest of The Parks was designed as an arboretum, the first trees were planted in 1865. A number of other features have been added over the years. Walter Sawyer has been superintendent of the Parks since 1991; the Parks has been the home ground of Oxford University Cricket Club since 1881. The cricket ground at The Parks was secured through the Master of Pembroke, Evan Evans obtaining a lease on 10 acres of land there in 1881.
The pavilion was designed by Thomas G. Jackson, architect of many nineteenth- and early twentieth-century Oxford buildings, including the University's Examination Schools; the building has three gables, the central one containing the clock, is topped by a cupola'of absurd height' and weather-vane. The pavilion contains a Long Room. Before moving to The Parks, the University Cricket Club had played on the Magdalen Ground and Bullingdon Green; the Magdalen Ground was used from the University Cricket Club's first match in 1829 to 1880 while Bullingdon Green was used for two matches in 1843. The cricket ground is the only first-class cricket ground in the UK where spectators can watch free of charge as admission cannot be charged for entry into the Parks; the club has therefore taken major matches to three other grounds in Oxford. The most used is the Christ Church Ground, which hosted 37 matches between 1878 and 1961. Twenty-one of these matches were against the Australians, played between 1882 and 1961.
The club used New College Ground for two matches in 1906 and 1907 against Yorkshire and the South Africans respectively. One match in 1912 against the South Africans was played at the Magdalen Ground; the club has played certain minor matches at the Merton College Ground, the St Edward's School Ground and the St Catherine's College Ground. The Parks has been, since 2000, home to the established ECB Oxford University Centre of Cricketing Excellence, a partnership between the University of Oxford, Oxford Brookes University and the England and Wales Cricket Board. Prior to the 2010 season the UCCE has been rebranded as Oxford Marylebone Cricket Club University; the University Match against Cambridge is the only one in which a true Oxford University Cricket Club team takes part: i.e. composed of current Oxford students. The Parks has, since 2002, hosted the first-class Varsity Match in even-numbered years; the Parks hosted two List A matches for the club and twenty-two matches for the Combined Universities in the Benson & Hedges Cup between 1973 and 1998.
The following features of the Parks are of special interest: Cricket pavilion — the pavilion was designed by Sir Thomas Jackson. The cricket ground and pavilion are used by the Oxford University Cricket Club; the two ends of the pitch are the Norham Gardens End. Seven large giant sequoias planted in about 1888. A duck pond with water lilies and a small island, constructed in 1925. High Bridge, built in 1923–24 as a relief project for the unemployed, it is called Rainbow Bridge, because of its shape. Genetic Garden — an experimental garden established by Professor Cyril Darlington to demonstrate evolutionary processes. Styphnolobium japonicum, known as the Japanese Pagoda Tree. Planted in 1888. Coronation Clump, a clump of trees planted to commemorate the coronation of Queen Elizabeth II in 1953. Parson's Pleasure, once now closed and part of the park. Dame's Delight Norham Manor estate Fenner's, where first-class cricket is played in Cambridge Oxford University Parks website Cricket in the Parks website View of University Park Looking Towards New College, Oxford by William Turner in the Metropolitan Museum of Art, New York City
University of Oxford
The University of Oxford is a collegiate research university in Oxford, England. There is evidence of teaching as early as 1096, making it the oldest university in the English-speaking world and the world's second-oldest university in continuous operation, it grew from 1167 when Henry II banned English students from attending the University of Paris. After disputes between students and Oxford townsfolk in 1209, some academics fled north-east to Cambridge where they established what became the University of Cambridge; the two'ancient universities' are jointly called'Oxbridge'. The history and influence of the University of Oxford has made it one of the most prestigious universities in the world; the university is made up of 38 constituent colleges, a range of academic departments, which are organised into four divisions. All the colleges are self-governing institutions within the university, each controlling its own membership and with its own internal structure and activities, it does not have a main campus, its buildings and facilities are scattered throughout the city centre.
Undergraduate teaching at Oxford is organised around weekly tutorials at the colleges and halls, supported by classes, lectures and laboratory work provided by university faculties and departments. It operates the world's oldest university museum, as well as the largest university press in the world and the largest academic library system nationwide. In the fiscal year ending 31 July 2018, the university had a total income of £2.237 billion, of which £579.1 million was from research grants and contracts. The university is ranked first globally by the Times Higher Education World University Rankings as of 2019 and is ranked as among the world's top ten universities, it is ranked second in all major national league tables, behind Cambridge. Oxford has educated many notable alumni, including 27 prime ministers of the United Kingdom and many heads of state and government around the world; as of 2019, 69 Nobel Prize winners, 3 Fields Medalists, 6 Turing Award winners have studied, worked, or held visiting fellowships at the University of Oxford, while its alumni have won 160 Olympic medals.
Oxford is the home of numerous scholarships, including the Rhodes Scholarship, one of the oldest international graduate scholarship programmes. The University of Oxford has no known foundation date. Teaching at Oxford existed in some form as early as 1096, but it is unclear when a university came into being, it grew from 1167 when English students returned from the University of Paris. The historian Gerald of Wales lectured to such scholars in 1188 and the first known foreign scholar, Emo of Friesland, arrived in 1190; the head of the university had the title of chancellor from at least 1201, the masters were recognised as a universitas or corporation in 1231. The university was granted a royal charter in 1248 during the reign of King Henry III. After disputes between students and Oxford townsfolk in 1209, some academics fled from the violence to Cambridge forming the University of Cambridge; the students associated together on the basis of geographical origins, into two'nations', representing the North and the South.
In centuries, geographical origins continued to influence many students' affiliations when membership of a college or hall became customary in Oxford. In addition, members of many religious orders, including Dominicans, Franciscans and Augustinians, settled in Oxford in the mid-13th century, gained influence and maintained houses or halls for students. At about the same time, private benefactors established colleges as self-contained scholarly communities. Among the earliest such founders were William of Durham, who in 1249 endowed University College, John Balliol, father of a future King of Scots. Another founder, Walter de Merton, a Lord Chancellor of England and afterwards Bishop of Rochester, devised a series of regulations for college life. Thereafter, an increasing number of students lived in colleges rather than in halls and religious houses. In 1333–34, an attempt by some dissatisfied Oxford scholars to found a new university at Stamford, was blocked by the universities of Oxford and Cambridge petitioning King Edward III.
Thereafter, until the 1820s, no new universities were allowed to be founded in England in London. The new learning of the Renaissance influenced Oxford from the late 15th century onwards. Among university scholars of the period were William Grocyn, who contributed to the revival of Greek language studies, John Colet, the noted biblical scholar. With the English Reformation and the breaking of communion with the Roman Catholic Church, recusant scholars from Oxford fled to continental Europe, settling at the University of Douai; the method of teaching at Oxford was transformed from the medieval scholastic method to Renaissance education, although institutions associated with the university suffered losses of land and revenues. As a centre of learning and scholarship, Oxford's reputation declined in the Age of Enlightenment. In 1636 William Laud, the chancellor and Archbishop of Canterbury, codified the university's statutes. These, to a large extent, remained its gove
A trail is a path, track or unpaved lane or road. In the United Kingdom and the Republic of Ireland path or footpath is the preferred term for a walking trail; the term is applied, in North America, to routes along rivers, sometimes to highways. In the US, the term was used for a route into or through wild territory used by emigrants. In the USA "trace" is a synonym for trail, as in Natchez Trace; some trails are single use and can only be used for walking, horse riding and cross-country skiing. There are unpaved trails used by dirt bikes and other off-road vehicles and in some places, like the Alps, trails are used for moving cattle and other livestock. In Australia, the term track can be used interchangeably with trail, can refer to anything from a dirt road to an unpaved pedestrian path. In New Zealand, the terms track or walkway are used exclusively except in reference to cross-country skiing: "walkways vary enormously in nature, from short urban strolls, to moderate coastal locations, to challenging tramps in the high country ".
Walkway is used in St. John's, Canada, where the "Grand Concourse", is an integrated walkway system. In the United Kingdom, the term trail is in common usage. Longer distance walking routes, government-promoted long distance paths, collectively known as National Trails, are frequently called ways; the term footpath is preferred for pedestrian routes, including long distance trails, is used for urban paths and sometimes in place of pavement. Track is used for wider paths used for hiking; the terms bridleway, restricted byway are all recognised legal terms and to a greater or lesser extent in general usage. The increased popularity of mountain biking has led to a proliferation of mountain bike trails in many countries; these will be grouped to form larger complexes, known as trail centers. In the early years of the 20th century, the term auto trail was used for a marked highway route, trail is now used to designate routes, including highway routes, designated for tourist interest like the Cabot Trail, Nova Scotia and the Quilt Trails in the US.
The term trail has been used by developers and urban planners for a variety of modern paved roads and boulevards, in these countries, some highways continue to be called a trail, such as the Susquehanna Trail in Pennsylvania, a designation that varies from a two-lane road to a four-lane freeway. A unusual use of the term is in the Canadian province of Alberta, which has multi-lane freeways called trails. Trail segregation, the practice of designating certain trails as having a specific preferred or exclusive use, is common and diverse. For example, bike trails are used not only on roads open to motor vehicles, but in trail systems open to other trail users; some trails are segregated for use by both equestrians and mountain bikes, or by equestrians only, or by mountain bikes only. Designated "wilderness area" trails may be segregated for non-wheeled use. Trail segregation for a particular use is accompanied by prohibitions against that use on other trails within the trail system. Trail segregation may be supported by signage, trail design and construction, by separation between parallel treads.
Separation may be achieved by "natural" barriers including distance, banking and vegetation, by "artificial" barriers including fencing and walls. Bicycle trails encompass a wide variety of trail types, including shared-use paths used for commuting, off-road cross country trails and downhill mountain bike trails; the number of off-road cycle trails has increased along with the popularity of mountain bikes. Off-road bicycle trails are function-specific and most waymarked along their route, they may form part of larger complexes, known as trail centres. Off-road trails incorporate a mix of challenging terrain, smooth fireroads, paved paths. Trails with an easy or moderate technical complexity are deemed cross-country trails, while trails difficult to experienced riders are more dubbed all-mountain, freeride, or downhill. Downhilling is popular at ski resorts such as Mammoth Mountain in California or Whistler Blackcomb in British Columbia, where ski lifts are used to get bikes and riders to the top of the mountain.
EuroVelo bicycle routes are a network of long-distance cycling routes criss-crossing Europe in various stages of completion, more than 45,000 km was in place by 2013. It is envisaged that the network will be complete by 2020 and when finished, the EuroVelo network's total length will exceed 70,000 km. EuroVelo is a project of the European Cyclists' Federation. EuroVelo routes can be used for bicycle touring across the continent, as well as by local people making short journeys; the routes are made of both existing national bike routes, such as the Dutch LF-Routes, the German D-Routes, the British National Cycle Network, existing general purpose roads, together with new stretches of cycle routes to connect them. Off-road cycling can cause soil erosion and habitat destruction if not carried out on established trails; this is so when trails are wet, overall though, cycling may have only as mu
Duck is the common name for a large number of species in the waterfowl family Anatidae which includes swans and geese. Ducks are divided among several subfamilies in the family Anatidae. Ducks are aquatic birds smaller than the swans and geese, may be found in both fresh water and sea water. Ducks are sometimes confused with several types of unrelated water birds with similar forms, such as loons or divers, grebes and coots; 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. This word replaced Old English ened/ænid "duck" 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. A duckling is a young duck in downy plumage or baby duck, but in the food trade a young domestic duck which has just reached adult size and bulk and its meat is still 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. The overall body plan of ducks is elongated and broad, the ducks are 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 broad and contains serrated lamellae, which are well defined in the filter-feeding species. In the case of some fishing species the bill is long and serrated; the scaled legs are strong and well developed, set far back on the body, more so in the aquatic species. The wings are strong and are short and pointed, the flight of ducks requires fast continuous strokes, requiring in turn strong wing muscles. Three species of steamer duck are flightless, however. Many species of duck are temporarily flightless; this moult precedes migration. The drakes of northern species have extravagant plumage, but, moulted in summer to give a more female-like appearance, the "eclipse" plumage. Southern resident species show less sexual dimorphism, although there are exceptions like the paradise shelduck of New Zealand, both strikingly sexually dimorphic and where the female's plumage is brighter than that of the male.
The plumage of juvenile birds 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, insects, small amphibians 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 submerging. Along the edge of the beak, there is a comb-like structure called a pecten; this strains the water squirting from traps any food. The pecten is used to preen feathers and to hold slippery food items. Diving ducks and sea ducks forage deep underwater. To be able to submerge more the diving ducks are heavier than dabbling ducks, therefore have more difficulty taking off to fly. A few specialized species such as the mergansers are adapted to 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, bulk jobs such as dredging out, turning head first, 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 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 monogamous, although these bonds last only a single year. Larger species and the more sedentary species tend to have pair-bonds that last numerous years. Most duck species breed once a year. Ducks tend to make a nest before breeding, after hatching, lead their ducklings to water. Mother ducks are 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 or are not prospering due to genetic defects or sickness brought about by hypothermia, starvation, or disease. Ducklings can be orphaned by inconsistent late hatching where a few eggs hatch after the mother has abandoned the nest and led her ducklings to water. Most domestic ducks neglect their eggs and ducklings, their eggs must be hatched under a broody hen or artificially.
Female mallard ducks make the classic "quack" sound while males make a similar but raspier sound, sometimes written as "breeeeze", but despite widespread misconceptions, most species of duck do not "quack". In general, ducks make a wide range of calls, ranging from whistles, cooing and grunts. For example, the scaup – which are diving ducks – make a noise like "scaup" (hence