1.
Bird
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Birds, a subgroup of Reptiles, are the last living examples of Dinosaurs. Birds live worldwide and range in size from the 5 cm bee hummingbird to the 2.75 m ostrich. They rank as the class of tetrapods with the most living species, at ten thousand. Birds are the closest living relatives of crocodilians, the fossil record indicates that birds evolved from feathered ancestors within the theropod group of saurischian dinosaurs. True birds first appeared during the Cretaceous period, around 100 million years ago, Birds, especially those in the southern continents, survived this event and then migrated to other parts of the world while diversifying during periods of global cooling. Primitive bird-like dinosaurs that lie outside class Aves proper, in the broader group Avialae, have been found dating back to the mid-Jurassic period, around 170 million years ago. Birds have wings which are more or less developed depending on the species, the digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have evolved for swimming. Many species annually migrate great distances, Birds are social, communicating with visual signals, calls, and bird songs, and participating in such social behaviours as cooperative breeding and hunting, flocking, and mobbing of predators. The vast majority of species are socially monogamous, usually for one breeding season at a time, sometimes for years. Other species have breeding systems that are polygynous or, rarely, Birds produce offspring by laying eggs which are fertilised through sexual reproduction. They are usually laid in a nest and incubated by the parents, most birds have an extended period of parental care after hatching. Some birds, such as hens, lay eggs even when not fertilised, songbirds, parrots, and other species are popular as pets. Guano is harvested for use as a fertiliser, Birds prominently figure throughout human culture. About 120–130 species have become extinct due to human activity since the 17th century, human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them. Recreational birdwatching is an important part of the ecotourism industry, the first classification of birds was developed by Francis Willughby and John Ray in their 1676 volume Ornithologiae. Carl Linnaeus modified that work in 1758 to devise the taxonomic classification system currently in use, Birds are categorised as the biological class Aves in Linnaean taxonomy. Phylogenetic taxonomy places Aves in the dinosaur clade Theropoda, Aves and a sister group, the clade Crocodilia, contain the only living representatives of the reptile clade Archosauria
2.
Reptile
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Reptiles are tetrapod animals in the class Reptilia, comprising todays turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives. The study of these traditional reptile orders, historically combined with that of amphibians, is called herpetology. Because some reptiles are more related to birds than they are to other reptiles. For this reason, many scientists prefer to consider the birds part of Reptilia as well. Some early examples include the lizard-like Hylonomus and Casineria, in addition to the living reptiles, there are many diverse groups that are now extinct, in some cases due to mass extinction events. In particular, the K–Pg extinction wiped out the pterosaurs, plesiosaurs, ornithischians, and sauropods, as well as species of theropods, crocodyliforms. Modern non-avian reptiles inhabit every continent with the exception of Antarctica, several living subgroups are recognized, Testudines, approximately 400 species, Sphenodontia,1 species, Squamata, over 9,600 species, Crocodilia,25 species, and Aves,10,000 species. Reptiles are tetrapod vertebrates, creatures that either have four limbs or, unlike amphibians, reptiles do not have an aquatic larval stage. As amniotes, reptile eggs are surrounded by membranes for protection and transport, many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals, with some providing initial care for their hatchlings. In the 18th century, the reptiles were, from the outset of classification, the terms reptile and amphibian were largely interchangeable, reptile being preferred by the French. Josephus Nicolaus Laurenti was the first to use the term Reptilia for an expanded selection of reptiles. Today, the two groups are commonly treated under the same heading as herptiles. He subsequently proposed the names of Sauropsida and Ichthyopsida for the two groups. In 1866, Haeckel demonstrated that vertebrates could be divided based on their strategies, and that reptiles, birds. The terms Sauropsida and Theropsida were used again in 1916 by E. S, Goodrich to distinguish between lizards, birds, and their relatives on the one hand and mammals and their extinct relatives on the other. Goodrich supported this division by the nature of the hearts and blood vessels in each group, according to Goodrich, both lineages evolved from an earlier stem group, Protosauria in which he included some animals today considered reptile-like amphibians, as well as early reptiles. Watson observed that the first two groups diverged very early in history, so he divided Goodrichs Protosauria between them. He also reinterpreted Sauropsida and Theropsida to exclude birds and mammals, thus his Sauropsida included Procolophonia, Eosuchia, Millerosauria, Chelonia, Squamata, Rhynchocephalia, Crocodilia, thecodonts, non-avian dinosaurs, pterosaurs, ichthyosaurs, and sauropterygians
3.
Feces
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Feces or faeces are the solid or semisolid metabolic waste from an animals digestive tract, discharged through the anus or cloaca during a process called defecation. Urine and feces together are called excreta, collected feces has various uses, namely as fertilizer or soil conditioner in agriculture, as a fuel source, or for medicinal purposes. After an animal has digested eaten material, the remains of material are discharged from its body as waste. Although it is lower in energy than the food from which it is derived, feces may retain a large amount of energy and this means that of all food eaten, a significant amount of energy remains for the decomposers of ecosystems. Many organisms feed on feces, from bacteria to fungi to insects such as dung beetles, some may specialize in feces, while others may eat other foods as well. Feces serve not only as a food, but also as a supplement to the usual diet of some animals. Feces and urine, which reflect light, are important to raptors such as kestrels. Seeds also may be found in feces, animals who eat fruit are known as frugivores. An advantage for a plant in having fruit is that animals will eat the fruit and this mode of seed dispersal is highly successful, as seeds dispersed around the base of a plant are unlikely to succeed and often are subject to heavy predation. Provided the seed can withstand the pathway through the system, it is not only likely to be far away from the parent plant. This cycling of matter is known as the biogeochemical cycle, the distinctive odor of feces is due to bacterial action. Gut flora produce compounds such as indole, skatole, and thiols and these are the same compounds that are responsible for the odor of flatulence. Consumption of foods prepared with spices may result in the spices being undigested, the perceived bad odor of feces has been hypothesized to be a deterrent for humans, as consuming or touching it may result in sickness or infection. Human perception of the odor may be contrasted by an animals perception of it, for example. In humans and depending on the individual and the circumstances, defecation may occur daily, extensive hardening of the feces may cause prolonged interruption in the routine and is called constipation. Human fecal matter varies significantly in appearance, depending on diet, normally it is semisolid, with a mucus coating. The brown coloration comes from a combination of bile and bilirubin, in newborn babies, initially fecal matter is yellow-green after the meconium. This coloration comes from the presence of bile alone, throughout the life of an ordinary human, one may experience many types of feces
4.
Invertebrate
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Invertebrates are animals that neither possess nor develop a vertebral column, derived from the notochord. This includes all animals apart from the subphylum Vertebrata, familiar examples of invertebrates include insects, crabs, lobsters and their kin, snails, clams, octopuses and their kin, starfish, sea-urchins and their kin, jellyfish, and worms. The majority of species are invertebrates, one estimate puts the figure at 97%. Many invertebrate taxa have a number and variety of species than the entire subphylum of Vertebrata. Some of the invertebrates, such as the Tunicata and Cephalochordata are more closely related to the vertebrates than to other invertebrates. This makes the term invertebrate paraphyletic and hence almost meaningless for taxonomic purposes, the word invertebrate comes from the form of the Latin word vertebra, which means a joint in general, and sometimes specifically a joint from the spinal column of a vertebrate. In turn the jointed aspect of vertebra derived from the concept of turning, coupled with the prefix in-, meaning not or without. The term invertebrates is not always precise among non-biologists since it does not accurately describe a taxon in the way that Arthropoda. Each of these describes an valid taxon, phylum, subphylum or family. Invertebrata is a term of convenience, not a taxon, it has very little circumscriptional significance except within the Chordata, the Vertebrata as a subphylum comprises such a small proportion of the Metazoa that to speak of the kingdom Animalia in terms of Vertebrata and Invertebrata has limited practicality. That would at least circumscribe the Chordata, however, even the notochord would be a less fundamental criterion than aspects of embryological development and symmetry or perhaps bauplan. The following text reflects earlier scientific understanding of the term and of animals which have constituted it. According to this understanding, invertebrates do not possess a skeleton of bone and they include hugely varied body plans. Many have fluid-filled, hydrostatic skeletons, like jellyfish or worms, others have hard exoskeletons, outer shells like those of insects and crustaceans. The most familiar invertebrates include the Protozoa, Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Echinodermata, Mollusca, Arthropoda include insects, crustaceans and arachnids. By far the largest number of described species are insects. The following table lists the number of described extant species for major invertebrate groups as estimated in the IUCN Red List of Threatened Species,2014.3. The IUCN estimates that 66,178 extant vertebrate species have been described, the trait that is common to all invertebrates is the absence of a vertebral column, this creates a distinction between invertebrates and vertebrates
5.
Sanitary sewer
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A sanitary sewer or foul sewer is an underground carriage system specifically for transporting sewage from houses and commercial buildings through pipes to treatment or disposal. Sanitary sewers are part of a system called sewerage or sewage system. Sewage may be treated to water pollution before discharge to surface waters. Sanitary sewers serving industrial areas also carry industrial wastewater, separate sanitary sewer systems are designed to transport sewage alone. In municipalities served by sewers, separate storm drains may be constructed to convey surface runoff directly to surface waters. Sanitary sewers are distinguished from combined sewers, which combine sewage with stormwater runoff in the same pipe, sanitary sewer systems are considered beneficial because they avoid combined sewer overflows. To overcome these disadvantages, some cities built separate sanitary sewers to collect only municipal wastewater, the decision between a combined sewer system or two separate systems is mainly based on need for sewage treatment and cost of providing treatment during heavy rain events. Many cities with combined sewer systems built prior to sewage treatment have not replaced those sewer systems, in the developed world, sewers are pipes from buildings to one or more levels of larger underground trunk mains, which transport the sewage to sewage treatment facilities. Vertical pipes, usually made of precast concrete, called manholes, depending upon site application and use, these vertical pipes can be cylindrical, eccentric or concentric. The manholes are used for access to the pipes for inspection and maintenance. They also facilitate vertical and horizontal angles in otherwise straight pipelines, pipes conveying sewage from an individual building to a common gravity sewer line are called laterals. Branch sewers typically run under streets receiving laterals from buildings along that street, larger cities may have sewers called interceptors receiving flow from multiple trunk sewers. Design and sizing of sanitary sewers considers the population to be served over the life of the sewer, per capita wastewater production. Commercial and industrial flows are considered, but diversion of surface runoff to storm drains eliminates wet weather flow peaks of inefficient combined sewers. Pumps may be necessary where gravity sewers serve areas at lower elevations than the treatment plant. A lift station is a gravity sewer sump with a pump to lift accumulated sewage to a higher elevation, the pump may discharge to another gravity sewer at that location or may discharge through a pressurized force main to some distant location. Most of the solids are removed by the tanks, so the treatment plant can be much smaller than a typical plant. In addition, because of the vast reduction in solid waste, because the wastestream is pressurized, they can be laid just below the ground surface along the lands contour
6.
Bird anatomy
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Bird anatomy, or the physiological structure of birds bodies, shows many unique adaptations, mostly aiding flight. The development of a beak has led to evolution of a specially adapted digestive system and these anatomical specializations have earned birds their own class in the vertebrate phylum. The bird skeleton is highly adapted for flight and it is extremely lightweight but strong enough to withstand the stresses of taking off, flying, and landing. One key adaptation is the fusing of bones into single ossifications, because of this, birds usually have a smaller number of bones than other terrestrial vertebrates. Birds also lack teeth or even a true jaw, instead having a beak, the beaks of many baby birds have a projection called an egg tooth, which facilitates their exit from the amniotic egg, and that falls off once it has done its job. Birds have many bones that are hollow with criss-crossing struts or trusses for structural strength, the number of hollow bones varies among species, though large gliding and soaring birds tend to have the most. Respiratory air sacs often form air pockets within the bones of the birds skeleton. The bones of diving birds are often less hollow than those of non-diving species, loons and puffins are without pneumatized bones entirely. Flightless birds, such as ostriches and emus, demonstrate osseous pneumaticity, possessing pneumatized femurs and, in the case of the emu, Birds also have more cervical vertebrae than many other animals, most have a highly flexible neck consisting of 13-25 vertebrae. Birds are the vertebrates to have fused clavicles or a keeled sternum or breastbone. The keel of the sternum serves as an attachment site for the used for flight or, similarly, for swimming. Again, flightless birds, such as ostriches, which do not have developed pectoral muscles. Swimming birds have a sternum, while walking birds have a long or high sternum and flying birds have a sternum width. Birds have uncinate processes on the ribs and these are hooked extensions of bone which help to strengthen the rib cage by overlapping with the rib behind them. This feature is found in the tuatara. They also have a greatly elongate tetradiate pelvis, similar to some reptiles, the hind limb has an intra-tarsal joint found also in some reptiles. There is extensive fusion of the vertebrae as well as fusion with the pectoral girdle. They have a skull, as in reptiles, with a pre-lachrymal fossa
7.
Common ostrich
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The ostrich or common ostrich is either one or two species of large flightless birds native to Africa, the only living member of the genus Struthio, which is in the ratite family. In 2014, the Somali ostrich was recognized as a distinct species, the common ostrich shares the order Struthioniformes with the kiwis, emus, rheas, and cassowaries. However, phylogenetic studies have shown that it is the group to all other members of Palaeognathae. It is distinctive in its appearance, with a neck and legs, and can run at up to about 70 km/h. The common ostrich is the largest living species of bird and lays the largest eggs of any living bird, the common ostrichs diet consists mainly of plant matter, though it also eats invertebrates. It lives in groups of 5 to 50 birds. When threatened, the ostrich will either hide itself by lying flat against the ground, if cornered, it can attack with a kick of its powerful legs. Mating patterns differ by region, but territorial males fight for a harem of two to seven females. The common ostrich is farmed around the world, particularly for its feathers and its skin is used for leather products and its meat is marketed commercially, with its leanness a common marketing point. Common ostriches usually weigh from 63 to 145 kilograms, or as much as two adult humans, ostriches of the East African race averaged 115 kg in males and 100 kg in females, while the nominate subspecies was found to average 111 kg in unsexed adults. Exceptional male ostriches can weigh up to 156.8 kg, at sexual maturity, male common ostriches can be from 2.1 to 2.8 m in height, while female common ostriches range from 1.7 to 2.0 m tall. New chicks are fawn in colour, with brown spots. During the first year of life, chicks grow at about 25 cm per month, at one year of age, common ostriches weigh approximately 45 kilograms. Their lifespan is up to 40–45 years, the feathers of adult males are mostly black, with white primaries and a white tail. However, the tail of one subspecies is buff, females and young males are greyish-brown and white. The head and neck of both male and female ostriches is nearly bare, with a layer of down. The skin of the neck and thighs is pinkish gray. The eyes are shaded from sunlight from above, However, the head and bill are relatively small for the birds huge size, with the bill measuring 12 to 14.3 cm
8.
Cassowary
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The cassowaries are ratites in the genus Casuarius and are native to the tropical forests of New Guinea, nearby islands, and northeastern Australia. The most common of these, the cassowary, is the third-tallest and second-heaviest living bird, smaller only than the ostrich. Cassowaries are very shy, but when provoked they are capable of inflicting injuries, occasionally fatal, to dogs, cassowaries are part of the ratite group, which also includes the emu, rheas, ostriches, and kiwi, and the extinct moas and elephant birds. g. The taxonomic name C. papuanus may also be in need of revision to Casuarius westermanni, the evolutionary history of cassowaries, as of all ratites, is not well known. A fossil species was reported from Australia, but for reasons of biogeography this assignment is not certain and it might belong to the prehistoric Emuarius, the northern and dwarf cassowaries are not well known. All cassowaries are usually shy birds of the deep forest, adept at disappearing long before a human knows they are there, even the more accessible southern cassowary of the far north Queensland rain forests is not well researched. Females are bigger and more brightly coloured, adult southern cassowaries are 1.5 to 1.8 m tall, although some females may reach 2 m, and weigh 58.5 kg. All cassowaries have feathers that consist of a shaft and loose barbules and they do not have retrices or a preen gland. Cassowaries have small wings with 5–6 large remeges and these are reduced to stiff, keratinous quills, like porcupine quills, with no barbs. A claw is on each second finger, the furcula and coracoid are degenerate, and their palatal bones and sphenoid bones touch each other. These, along with their body, are thought to be adaptations to ward off vines, thorns. Cassowaries have three-toed feet with sharp claws, the second toe, the inner one in the medial position, sports a dagger-like claw that can be 125 mm long. This claw is particularly fearsome since cassowaries sometimes kick humans and animals with their powerful legs. Cassowaries can run at up to 50 km/h through the dense forest and they are good swimmers, crossing wide rivers and swimming in the sea. All three species have a keratinous skin-covered casque on their heads which grows with age, the casques shape and size, up to 18 cm, is species-dependent. Casuarius casuarius has the largest and Casuarius bennetti the smallest, with Casuarius unappendiculatus having variations in between, contrary to earlier findings, the hollow inside of the casque is spanned with fine fibres which are believed to have an acoustic function. Several functions for the casque have been proposed, one is that they are a secondary sexual characteristic. Other suggested functions include being used to batter through underbrush, as a weapon in dominance disputes, the latter three are disputed by biologist Andrew Mack, whose personal observation suggests that the casque amplifies deep sounds
9.
Kiwi
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Kiwi or kiwis are flightless birds native to New Zealand, in the genus Apteryx and family Apterygidae. At around the size of a chicken, kiwi are by far the smallest living ratites. DNA sequence comparisons have yielded the surprising conclusion that kiwi are much more related to the extinct Malagasy elephant birds than to the moa with which they shared New Zealand. There are five recognised species, two of which are vulnerable, one of which is endangered, and one of which is critically endangered. All species have negatively affected by historic deforestation but currently the remaining large areas of their forest habitat are well protected in reserves. At present, the greatest threat to their survival is predation by mammalian predators. The kiwi is a symbol of New Zealand, and the association is so strong that the term Kiwi is used internationally as the colloquial demonym for New Zealanders. The Māori language word kiwi is generally accepted to be of imitative origin from the call, with its long decurved bill and brown body, the curlew resembles the kiwi. So when the first Polynesian settlers arrived, they may have applied the word kiwi to the new-found bird, the genus name Apteryx is derived from Ancient Greek without wing, a-, without or not, pterux, wing. The name is usually uncapitalised, with the either the anglicised kiwis or, consistent with the Māori language. There are five species of kiwi, as well as a number of subspecies. Relationships in the genus Apteryx The largest species is the great spotted kiwi or Roroa, Apteryx haastii and it has grey-brown plumage with lighter bands. The female lays just one egg, which both parents then incubate, the population is estimated to be over 20,000, distributed through the more mountainous parts of northwest Nelson, the northern West Coast, and the Southern Alps. The small little spotted kiwi, Apteryx owenii is unable to withstand predation by introduced pigs, stoats and cats, about 1350 remain on Kapiti Island. It has been introduced to other islands and appears to be becoming established with about 50 Little Spots on each island. A docile bird the size of a bantam, it stands 25 cm high and she lays one egg, which is incubated by the male. Females lay as many as three eggs in a season, each one in a different nest, the distribution of these kiwi is limited to a small area on the west coast of the South Island of New Zealand. The southern brown kiwi, Tokoeka, or Common kiwi, Apteryx australis, is a common species of kiwi, known from south and west parts of the South Island
10.
Goose
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Geese are waterfowl belonging to the tribe Anserini of the family Anatidae. This tribe comprises the genera Anser, Branta and Chen, some other birds, mostly related to the shelducks, have goose as part of their names. More distantly related members of the family Anatidae are swans, most of which are larger than true geese, and ducks, the word goose is a direct descendent of Proto-Indo-European root, *ghans-. In Germanic languages, the root gave Old English gōs with the plural gēs and gandres, Frisian goes, gies and guoske, New High German Gans, Gänse, and Ganter, and Old Norse gās. The term goose applies to the female in particular, while applies to the male in particular. Young birds before fledging are called goslings, the collective noun for a group of geese on the ground is a gaggle, when in flight, they are called a skein, a team, or a wedge, when flying close together, they are called a plump. The three living genera of true geese are, Anser, grey geese, including the goose, and domestic geese, Chen, white geese. Either these or, more probably, the goose-like Coscoroba swan is the closest living relative of the true geese, the aptly named Anser atavus from some 12 million years ago had even more plesiomorphies in common with swans. In addition, some birds are known from subfossil remains found on the Hawaiian Islands. Geese are monogamous, living in permanent pairs throughout the year, however, unlike most other permanently monogamous animals, paired geese are more dominant and feed more, two factors that result in more young. Some mainly Southern Hemisphere birds are called geese, most of which belong to the shelduck subfamily Tadorninae, the blue-winged goose, Cyanochen cyanopterus, and the Cape Barren goose, Cereopsis novaehollandiae, have disputed affinities. They belong to separate ancient lineages that may ally either to the Tadorninae, Anserinae, the three species of small waterfowl in the genus Nettapus are named pygmy geese. They seem to represent another ancient lineage, with affinities to the Cape Barren goose or the spur-winged goose. A genus of prehistorically extinct seaducks, Chendytes, is sometimes called diving-geese due to their large size, the unusual magpie goose is in a family of its own, the Anseranatidae. The northern gannet, a seabird, is known as the Solan goose, although it is a bird unrelated to the true geese. Well-known sayings about geese include, To have a gander is to something in detail. Whats sauce for the goose is sauce for the means that what is appropriate treatment for one person is equally appropriate for someone else. Saying that someones goose is cooked means that they have suffered, or are about to suffer, a wild goose chase is a useless, futile waste of time and effort
11.
Swan
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Swans are birds of the family Anatidae within the genus Cygnus. The swans close relatives include the geese and ducks, Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a subfamily, Cygninae. There are six or seven species of swan in the genus Cygnus, in there is another species known as the coscoroba swan. Swans usually mate for life, though divorce does sometimes occur, particularly following nesting failure, and if a mate dies, the number of eggs in each clutch ranges from three to eight. The English word swan, akin to the German Schwan, Dutch zwaan, an adult male is a cob, from Middle English cobbe, an adult female is a pen. Swans are the largest extant members of the waterfowl family Anatidae, the largest species, including the mute swan, trumpeter swan, and whooper swan, can reach a length of over 1.5 m and weigh over 15 kg. Their wingspans can be over 3.1 m, compared to the closely related geese, they are much larger and have proportionally larger feet and necks. Adults also have a patch of unfeathered skin between the eyes and bill, the sexes are alike in plumage, but males are generally bigger and heavier than females. The Northern Hemisphere species of swan have pure white plumage but the Southern Hemisphere species are mixed black, the Australian black swan is completely black except for the white flight feathers on its wings, the chicks of black swans are light grey. The South American black-necked swan has a body with a black neck. The legs of swans are normally a dark grey colour. Bill colour varies, the four species have black bills with varying amounts of yellow. The mute swan and black-necked swan have lumps at the base of their bills on the upper mandible, Swans are generally found in temperate environments, rarely occurring in the tropics. A group of swans is called a bevy or a wedge in flight, four species occur in the Northern Hemisphere, one species is found in Australia and New Zealand and one species is distributed in southern South America. They are absent from tropical Asia, Central America, northern South America, one species, the mute swan, has been introduced to North America, Australia and New Zealand. Several species are migratory, either wholly or partly so, the mute swan is a partial migrant, being resident over areas of Western Europe but wholly migratory in Eastern Europe and Asia. The whooper swan and tundra swan are wholly migratory, and the swans are almost entirely migratory
12.
Duck
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Duck is the common name for a large number of species in the waterfowl family Anatidae, which also includes swans and geese. The ducks are divided among several subfamilies in the family Anatidae, they do not represent a group but a form taxon, since swans. Ducks are mostly birds, mostly smaller than the swans and geese. Ducks are sometimes confused with several types of unrelated water birds with similar forms, such as loons or divers, grebes, gallinules and 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, the word ened/ænid was inherited from Proto-Indo-European, compare, Latin anas duck, Lithuanian ántis duck, Ancient Greek nēssa/nētta duck, and Sanskrit ātí water bird, among others. A duckling is a duck in downy plumage or baby duck. A male duck is called a drake and the female is called a duck, 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, 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 strong and are generally short and pointed. Three species of 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, 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. The plumage of 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 exploit 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, 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, 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, to avoid injury when digging into sediment it has no cere, but the nostrils come out through hard horn
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