Corvidae is a cosmopolitan family of oscine passerine birds that contains the crows, rooks, jays, treepies and nutcrackers. In common English, they are known as the crow family, or, more technically, corvids. Over 120 species are described; the genus Corvus, including the jackdaws, crows and ravens, makes up over a third of the entire family. Corvids display remarkable intelligence for animals of their size and are among the most intelligent birds thus far studied. Members of the family have demonstrated self-awareness in mirror tests and tool-making ability, skills which until were thought to be possessed only by humans and a few other higher mammals, their total brain-to-body mass ratio is equal to that of non-human great apes and cetaceans, only lower than that of humans. They are medium to large in size, with strong feet and bills, rictal bristles, a single moult each year. Corvids are found worldwide except for the tip of the polar ice caps; the majority of the species are found in tropical South and Central America, southern Asia and Eurasia, with fewer than 10 species each in Africa and Australasia.
The genus Corvus has re-entered Australia in recent geological prehistory, with five species and one subspecies there. Several species of raven have reached oceanic islands, some of these species are now threatened with extinction or have become extinct; the family Corvidae was introduced by the English zoologist William Elford Leach in a guide to the contents of the British Museum published in 1820. Over the years, much disagreement has arisen on the exact evolutionary relationships of the corvid family and their relatives. What seemed clear was that corvids are derived from Australasian ancestors and from there spread throughout the world. Other lineages derived from these ancestors evolved into ecologically diverse, but Australasian groups. In the late 1970s and throughout the 1980s, Sibley and Ahlquist united the corvids with other taxa in the Corvida, based on DNA–DNA hybridization; the presumed corvid relatives included currawongs, birds of paradise, quail-thrushes, monarch flycatchers and drongos, shrikes and vangas, but current research favors the theory that this grouping is artificial.
The corvids constitute the core group of the Corvoidea, together with their closest relatives. They are the core group of the Corvida, which includes the related groups, such as Old World orioles and vireos. Clarification of the interrelationships of the corvids has been achieved based on cladistic analysis of several DNA sequences; the jays and magpies do not constitute monophyletic lineages, but rather seem to split up into an American and Old World lineage, an Holarctic and Oriental lineage, respectively. These are not related among each other; the position of the azure-winged magpie, which has always been a major enigma, is less clear than before. The crested jay is traditionally included in the Corvidae, but might not be a true member of this family being closer to the helmetshrikes or shrikes; the Hume's ground "jay" is in fact a member of the tit family Paridae. The following tree represents current insights in the phylogeny of the Crow family according to J. Boyd; the earliest corvid fossils date to the mid-Miocene, about 17 million years ago.
The known prehistoric corvid genera appear to be of the New World and Old World jay and Holarctic magpie lineages: Miocorvus Miopica Miocitta Corvidae gen. et sp. indet. Protocitta Corvidae gen. et sp. indet. - belongs in an extant genus Henocitta In addition, there are numerous fossil species of extant genera since the Mio–Pliocene European Corvus. Corvids are large to large passerines with a robust build, strong legs and all species except the pinyon jay have nostrils covered by bristle-like feathers. Many corvids of temperate zones have black or blue coloured plumage; the sexes are similar in color and size. Corvids have stout bills and large wingspans; the family includes the largest members of the passerine order. The smallest corvid is the dwarf jay, at 21.5 cm. The largest corvids are the common raven and the thick-billed raven, both of which exceed 1,400 grams and 65 cm. Species can be identified based on size and geography. Corvids occur in most climatic zones. Most do not migrate significantly.
However, during a shortage of food, eruptive migration can occur. When species are migratory, they will form large flocks in the travel south. One reason for the success of crows, compared to ravens, is their ability to overlap breeding territory. During breeding season, cr
Birds known as Aves, are a group of endothermic vertebrates, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, a strong yet lightweight skeleton. Birds range in size from the 5 cm bee hummingbird to the 2.75 m ostrich. They rank as the world's most numerically-successful class of tetrapods, with ten thousand living species, more than half of these being passerines, sometimes known as perching birds. Birds have wings which are less developed depending on the species. Wings, which evolved from forelimbs, gave birds the ability to fly, although further evolution has led to the loss of flight in flightless birds, including ratites and diverse endemic island species of birds; the digestive and respiratory systems of birds are uniquely adapted for flight. Some bird species of aquatic environments seabirds and some waterbirds, have further evolved for swimming; the fossil record demonstrates that birds are modern feathered dinosaurs, having evolved from earlier feathered dinosaurs within the theropod group, which are traditionally placed within the saurischian dinosaurs.
The closest living relatives of birds are the crocodilians. 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. Many of these early "stem-birds", such as Archaeopteryx, were not yet capable of powered flight, many retained primitive characteristics like toothy jaws in place of beaks, long bony tails. DNA-based evidence finds that birds diversified around the time of the Cretaceous–Palaeogene extinction event 66 million years ago, which killed off the pterosaurs and all the non-avian dinosaur lineages, but birds those in the southern continents, survived this event and migrated to other parts of the world while diversifying during periods of global cooling. This makes them the sole surviving dinosaurs according to cladistics; some birds corvids and parrots, are among the most intelligent animals. Many species annually migrate great distances. Birds are social, communicating with visual signals and bird songs, participating in such social behaviours as cooperative breeding and hunting and mobbing of predators.
The vast majority of bird species are monogamous for one breeding season at a time, sometimes for years, but for life. Other species have breeding systems that are polygynous or polyandrous. Birds produce offspring by laying eggs, they are 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 when not fertilised, though unfertilised eggs do not produce offspring. Many species of birds are economically important as food for human consumption and raw material in manufacturing, with domesticated and undomesticated birds being important sources of eggs and feathers. Songbirds 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, hundreds more before then. 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 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. During the late 1990s, Aves was most defined phylogenetically as all descendants of the most recent common ancestor of modern birds and Archaeopteryx lithographica. However, an earlier definition proposed by Jacques Gauthier gained wide currency in the 21st century, is used by many scientists including adherents of the Phylocode system. Gauthier defined Aves to include only the crown group of the set of modern birds; this was done by excluding most groups known only from fossils, assigning them, instead, to the Avialae, in part to avoid the uncertainties about the placement of Archaeopteryx in relation to animals traditionally thought of as theropod dinosaurs.
Gauthier identified four different definitions for the same biological name "Aves", a problem. Gauthier proposed to reserve the term Aves only for the crown group consisting of the last common ancestor of all living birds and all of its descendants, which corresponds to meaning number 4 below, he assigned other names to the other groups. Aves can mean all archosaurs closer to birds than to crocodiles Aves can mean those advanced archosaurs with feathers Aves can mean those feathered dinosaurs that fly Aves can mean the last common ancestor of all the living birds and all of its descendants (a "c
Antarctica is Earth's southernmost continent. It contains the geographic South Pole and is situated in the Antarctic region of the Southern Hemisphere entirely south of the Antarctic Circle, is surrounded by the Southern Ocean. At 14,200,000 square kilometres, it is the fifth-largest continent. For comparison, Antarctica is nearly twice the size of Australia. About 98% of Antarctica is covered by ice that averages 1.9 km in thickness, which extends to all but the northernmost reaches of the Antarctic Peninsula. Antarctica, on average, is the coldest and windiest continent, has the highest average elevation of all the continents. Most of Antarctica is a polar desert, with annual precipitation of only 200 mm along the coast and far less inland; the temperature in Antarctica has reached −89.2 °C, though the average for the third quarter is −63 °C. Anywhere from 1,000 to 5,000 people reside throughout the year at research stations scattered across the continent. Organisms native to Antarctica include many types of algae, fungi, plants and certain animals, such as mites, penguins and tardigrades.
Vegetation, where it occurs, is tundra. Antarctica is noted as the last region on Earth in recorded history to be discovered, unseen until 1820 when the Russian expedition of Fabian Gottlieb von Bellingshausen and Mikhail Lazarev on Vostok and Mirny sighted the Fimbul ice shelf; the continent, remained neglected for the rest of the 19th century because of its hostile environment, lack of accessible resources, isolation. In 1895, the first confirmed. Antarctica is a de facto condominium, governed by parties to the Antarctic Treaty System that have consulting status. Twelve countries signed the Antarctic Treaty in 1959, thirty-eight have signed it since then; the treaty prohibits military activities and mineral mining, prohibits nuclear explosions and nuclear waste disposal, supports scientific research, protects the continent's ecozone. Ongoing experiments are conducted by more than 4,000 scientists from many nations; the name Antarctica is the romanised version of the Greek compound word ἀνταρκτική, feminine of ἀνταρκτικός, meaning "opposite to the Arctic", "opposite to the north".
Aristotle wrote in his book Meteorology about an Antarctic region in c. 350 BC Marinus of Tyre used the name in his unpreserved world map from the 2nd century CE. The Roman authors Hyginus and Apuleius used for the South Pole the romanised Greek name polus antarcticus, from which derived the Old French pole antartike attested in 1270, from there the Middle English pol antartik in a 1391 technical treatise by Geoffrey Chaucer. Before acquiring its present geographical connotations, the term was used for other locations that could be defined as "opposite to the north". For example, the short-lived French colony established in Brazil in the 16th century was called "France Antarctique"; the first formal use of the name "Antarctica" as a continental name in the 1890s is attributed to the Scottish cartographer John George Bartholomew. The long-imagined south polar continent was called Terra Australis, sometimes shortened to'Australia' as seen in a woodcut illustration titled Sphere of the winds, contained in an astrological textbook published in Frankfurt in 1545.
Although the longer Latin phrase was better known, the shortened name Australia was used in Europe's scholarly circles. In the nineteenth century, the colonial authorities in Sydney removed the Dutch name from New Holland. Instead of inventing a new name to replace it, they took the name Australia from the south polar continent, leaving it nameless for some eighty years. During that period, geographers had to make do with clumsy phrases such as "the Antarctic Continent", they searched for a more poetic replacement, suggesting various names such as Antipodea. Antarctica was adopted in the 1890s. Antarctica has no indigenous population, there is no evidence that it was seen by humans until the 19th century. However, in February 1775, during his second voyage, Captain Cook called the existence of such a polar continent "probable" and in another copy of his journal he wrote:" believe it and it's more than probable that we have seen a part of it". However, belief in the existence of a Terra Australis—a vast continent in the far south of the globe to "balance" the northern lands of Europe and North Africa—had prevailed since the times of Ptolemy in the 1st century AD.
In the late 17th century, after explorers had found that South America and Australia were not part of the fabled "Antarctica", geographers believed that the continent was much larger than its actual size. Integral to the story of the origin of Antarctica's name is that it was not named Terra Australis—this name was given to Australia instead, because of the misconception that no significant landmass could exist further south. Explorer Matthew Flinders, in particular, has been credited with popularising the transfer of the name Terra Australis to Australia, he justified the titling of his book A Voyage to Terra Australis by writing in the introduction: There is no probability, that any other detached body of land, of nearly equal extent, will be found in a more southern latitude.
Voles are small rodents that are relatives of mice, but with a stouter body. They are sometimes known as meadow mice or field mice in North Australia. Vole species form the subfamily Arvicolinae with the muskrats. There are 155 different vole species, they are small rodents that grow depending on the species. Females can have five to 10 litters per year. Gestation lasts for the young voles reach sexual maturity in a month; as a result of this biological exponential growth, vole populations can grow large within a short time. Since litters average five to 10 young, a mating pair can birth a hundred more voles in a year. Voles outwardly resemble several other small animals. Moles, mice and shrews have similar characteristics and behavioral tendencies. Voles thrive on small plants yet, like shrews, they will eat dead animals and, like mice or rats, they can live on any nut or fruit. In addition, voles target plants more than most other small animals. Voles girdle small trees and ground cover much like a porcupine.
This girdling can kill young plants and is not healthy for trees or other shrubs. Voles eat succulent root systems and burrow under plants or ground cover and eat away until the plant is dead. Bulbs in the ground are another favorite target for voles; the presence of large numbers of voles is only identifiable after they have destroyed a number of plants. However, like other burrowing rodents, they play beneficial roles, including dispersing nutrients throughout the upper soil layers. Many predators eat voles, including martens, hawks, coyotes, foxes, snakes and lynxes. Vole bones are found in the pellets of the short-eared owl, the northern spotted owl, the saw-whet owl, the barn owl, the great gray owl, the northern pygmy owl; the average life of the smaller vole species is three to six months. These voles live longer than 12 months. Larger species, such as the European water vole, live longer and die during their second, or their third, winter; as many as 88% of voles are estimated to die within the first month of life.
The prairie vole is a notable animal model for its monogamous sexual fidelity, since the male is faithful to the female, shares in the raising of pups. The woodland vole is usually monogamous. Another species from the same genus, the meadow vole, has promiscuously mating males, scientists have changed adult male meadow voles' behavior to resemble that of prairie voles in experiments in which a single gene was introduced into the brain by a virus; the behavior is influenced by the number of repetitions of a particular string of microsatellite DNA. Male prairie voles with the longest DNA strings spend more time with their mates and pups than male prairie voles with shorter strings. However, other scientists have disputed the gene's relationship to monogamy, cast doubt on whether the human version plays an analogous role. Physiologically, pair-bonding behavior has been shown to be connected to vasopressin and oxytocin levels, with the genetic influence arising via the number of receptors for these substances in the brain.
Voles have a number of unusual chromosomal traits. Species have been found with 17 to 64 chromosomes. In some species and females have different chromosome numbers, a trait unusual in mammals, though it is seen in other organisms. Additionally, genetic material found on the Y chromosome has been found in both males and females in at least one species. In another species, the X chromosome contains 20% of the genome. All of these variations result in little physical aberration; the genus microtus mating system includes both monogamous and polygamous behaviors which induces differing patterns in mate choice and parental care. Environmental conditions have shown to be a large part in dictating which system is active in a given population, as a result this can be understood as a plastic mating system. In any species, mating systems are driven to most efficiently reproduce by allocating time and energy as best fit. Voles live in colonies due to the young remaining in the family group for long periods.
In the microtus genus monogamy is preferred when resources are spatially homogenous and population densities are low and where the opposite of both conditions are realized polygamous tendencies arise. Vole mating systems are sensitive to the operation sex ratio and are found to tend toward monogamy when the ratios of males to females is 1, where this ratio is greater than 1 and more males are present or less than 1 and more females are present polygamy is induced However the most marked effect on mating system is population density and these effects can take place both inter and intra-specificallyMale voles are shown to be territorial and tend to include territories of several female voles when possible, under these conditions polyandry exists and low male parental care is offered. Males mark and aggressively defend their territories and such marking initiate female preference where females are found to prefer males with the most recent marking in a given areaFemale and male preference are shown to be for familiar mat
Fossilworks is a portal which provides query and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. Fossilworks is housed at Macquarie University, it includes many analysis and data visualization tools included in the Paleobiology Database. "Fossilworks". Retrieved 2010-04-08
Owls are birds from the order Strigiformes, which includes about 200 species of solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, feathers adapted for silent flight. Exceptions include the gregarious burrowing owl. Owls hunt small mammals and other birds, although a few species specialize in hunting fish, they are found in all regions of the Earth except some remote islands. Owls are divided into two families: the true owl family and the barn-owl family, Tytonidae. Owls possess large, forward-facing eyes and ear-holes, a hawk-like beak, a flat face, a conspicuous circle of feathers, a facial disc, around each eye; the feathers making up this disc can be adjusted to focus sounds from varying distances onto the owls' asymmetrically placed ear cavities. Most birds of prey have eyes on the sides of their heads, but the stereoscopic nature of the owl's forward-facing eyes permits the greater sense of depth perception necessary for low-light hunting.
Although owls have binocular vision, their large eyes are fixed in their sockets—as are those of most other birds—so they must turn their entire heads to change views. As owls are farsighted, they are unable to see anything within a few centimeters of their eyes. Caught prey can be felt by owls with the use of filoplumes—hairlike feathers on the beak and feet that act as "feelers", their far vision in low light, is exceptionally good. Owls can rotate their heads and necks as much as 270°. Owls have 14 neck vertebrae compared to seven in humans, they have adaptations to their circulatory systems, permitting rotation without cutting off blood to the brain: the foramina in their vertebrae through which the vertebral arteries pass are about 10 times the diameter of the artery, instead of about the same size as the artery as in humans. Other anastomoses between the carotid and vertebral arteries support this effect; the smallest owl—weighing as little as 31 g and measuring some 13.5 cm —is the elf owl.
Around the same diminutive length, although heavier, are the lesser known long-whiskered owlet and Tamaulipas pygmy owl. The largest owls are two sized eagle owls; the largest females of these species are 71 cm long, have 54 cm long wings, weigh 4.2 kg. Different species of owls produce different sounds; as noted above, their facial discs help owls to funnel the sound of prey to their ears. In many species, these discs are placed asymmetrically, for better directional location. Owl plumage is cryptic, although several species have facial and head markings, including face masks, ear tufts, brightly coloured irises; these markings are more common in species inhabiting open habitats, are thought to be used in signaling with other owls in low-light conditions. Sexual dimorphism is a physical difference between females of a species. Reverse sexual dimorphism, when females are larger than males, has been observed across multiple owl species; the degree of size dimorphism varies across multiple populations and species, is measured through various traits, such as wing span and body mass.
Overall, female owls tend to be larger than males. The exact explanation for this development in owls is unknown. However, several theories explain the development of sexual dimorphism in owls. One theory suggests that selection has led males to be smaller because it allows them to be efficient foragers; the ability to obtain more food is advantageous during breeding season. In some species, female owls stay at their nest with their eggs while it is the responsibility of the male to bring back food to the nest. However, if food is scarce, the male first feeds himself before feeding the female. Small birds, which are agile, are an important source of food for owls. Male burrowing owls have been observed to have longer wing chords than females, despite being smaller than females. Furthermore, owls have been observed to be the same size as their prey; this has been observed in other predatory birds, which suggests that owls with smaller bodies and long wing chords have been selected for because of the increased agility and speed that allows them to catch their prey.
Another popular theory suggests that females have not been selected to be smaller like male owls because of their sexual roles. In many species, female owls may not leave the nest. Therefore, females may have a larger mass to allow them to go for a longer period of time without starving. For example, one hypothesized sexual role is that larger females are more capable of dismembering prey and feeding it to their young, hence female owls are larger than their male counterparts. A different theory suggests that the size difference between male and females is due to sexual selection: since large females can choose their mate and may violently reject a male's sexual advances, smaller male owls that have the ability to escape unreceptive females are more to have been selected. All owls are carnivorous bi
Australia the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. It is the world's sixth-largest country by total area; the neighbouring countries are Papua New Guinea and East Timor to the north. The population of 25 million is urbanised and concentrated on the eastern seaboard. Australia's capital is Canberra, its largest city is Sydney; the country's other major metropolitan areas are Melbourne, Brisbane and Adelaide. Australia was inhabited by indigenous Australians for about 60,000 years before the first British settlement in the late 18th century, it is documented. After the European exploration of the continent by Dutch explorers in 1606, who named it New Holland, Australia's eastern half was claimed by Great Britain in 1770 and settled through penal transportation to the colony of New South Wales from 26 January 1788, a date which became Australia's national day; the population grew in subsequent decades, by the 1850s most of the continent had been explored and an additional five self-governing crown colonies established.
On 1 January 1901, the six colonies federated. Australia has since maintained a stable liberal democratic political system that functions as a federal parliamentary constitutional monarchy, comprising six states and ten territories. Being the oldest and driest inhabited continent, with the least fertile soils, Australia has a landmass of 7,617,930 square kilometres. A megadiverse country, its size gives it a wide variety of landscapes, with deserts in the centre, tropical rainforests in the north-east and mountain ranges in the south-east. A gold rush began in Australia in the early 1850s, its population density, 2.8 inhabitants per square kilometre, remains among the lowest in the world. Australia generates its income from various sources including mining-related exports, telecommunications and manufacturing. Indigenous Australian rock art is the oldest and richest in the world, dating as far back as 60,000 years and spread across hundreds of thousands of sites. Australia is a developed country, with the world's 14th-largest economy.
It has a high-income economy, with the world's tenth-highest per capita income. It is a regional power, has the world's 13th-highest military expenditure. Australia has the world's ninth-largest immigrant population, with immigrants accounting for 26% of the population. Having the third-highest human development index and the eighth-highest ranked democracy globally, the country ranks in quality of life, education, economic freedom, civil liberties and political rights, with all its major cities faring well in global comparative livability surveys. Australia is a member of the United Nations, G20, Commonwealth of Nations, ANZUS, Organisation for Economic Co-operation and Development, World Trade Organization, Asia-Pacific Economic Cooperation, Pacific Islands Forum and the ASEAN Plus Six mechanism; the name Australia is derived from the Latin Terra Australis, a name used for a hypothetical continent in the Southern Hemisphere since ancient times. When Europeans first began visiting and mapping Australia in the 17th century, the name Terra Australis was applied to the new territories.
Until the early 19th century, Australia was best known as "New Holland", a name first applied by the Dutch explorer Abel Tasman in 1644 and subsequently anglicised. Terra Australis still saw occasional usage, such as in scientific texts; the name Australia was popularised by the explorer Matthew Flinders, who said it was "more agreeable to the ear, an assimilation to the names of the other great portions of the earth". The first time that Australia appears to have been used was in April 1817, when Governor Lachlan Macquarie acknowledged the receipt of Flinders' charts of Australia from Lord Bathurst. In December 1817, Macquarie recommended to the Colonial Office. In 1824, the Admiralty agreed that the continent should be known by that name; the first official published use of the new name came with the publication in 1830 of The Australia Directory by the Hydrographic Office. Colloquial names for Australia include "Oz" and "the Land Down Under". Other epithets include "the Great Southern Land", "the Lucky Country", "the Sunburnt Country", "the Wide Brown Land".
The latter two both derive from Dorothea Mackellar's 1908 poem "My Country". Human habitation of the Australian continent is estimated to have begun around 65,000 to 70,000 years ago, with the migration of people by land bridges and short sea-crossings from what is now Southeast Asia; these first inhabitants were the ancestors of modern Indigenous Australians. Aboriginal Australian culture is one of the oldest continual civilisations on earth. At the time of first European contact, most Indigenous Australians were hunter-gatherers with complex economies and societies. Recent archaeological finds suggest. Indigenous Australians have an oral culture with spiritual values based on reverence for the land and a belief in the Dreamtime; the Torres Strait Islanders, ethnically Melanesian, obtained their livelihood from seasonal horticulture and the resources of their reefs and seas. The northern coasts and waters of Australia were visited s