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
The Precambrian is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic eon, named after Cambria, the Latinised name for Wales, where rocks from this age were first studied; the Precambrian accounts for 88% of the Earth's geologic time. The Precambrian is an informal unit of geologic time, subdivided into three eons of the geologic time scale, it spans from the formation of Earth about 4.6 billion years ago to the beginning of the Cambrian Period, about 541 million years ago, when hard-shelled creatures first appeared in abundance. Little is known about the Precambrian, despite it making up seven-eighths of the Earth's history, what is known has been discovered from the 1960s onwards; the Precambrian fossil record is poorer than that of the succeeding Phanerozoic, fossils from the Precambrian are of limited biostratigraphic use. This is because many Precambrian rocks have been metamorphosed, obscuring their origins, while others have been destroyed by erosion, or remain buried beneath Phanerozoic strata.
It is thought that the Earth coalesced from material in orbit around the Sun at 4,543 Ma, may have been struck by a large planetesimal shortly after it formed, splitting off material that formed the Moon. A stable crust was in place by 4,433 Ma, since zircon crystals from Western Australia have been dated at 4,404 ± 8 Ma; the term "Precambrian" is recognized by the International Commission on Stratigraphy as the only "supereon" in geologic time. "Precambrian" is still used by geologists and paleontologists for general discussions not requiring the more specific eon names. As of 2010, the United States Geological Survey considers the term informal, lacking a stratigraphic rank. A specific date for the origin of life has not been determined. Carbon found in 3.8 billion-year-old rocks from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have been found in Western Australia. Probable fossils 100 million years older have been found in the same area.
However, there is evidence. There is a solid record of bacterial life throughout the remainder of the Precambrian. Excluding a few contested reports of much older forms from North America and India, the first complex multicellular life forms seem to have appeared at 1500 Ma, in the Mesoproterozoic era of the Proterozoic eon. Fossil evidence from the Ediacaran period of such complex life comes from the Lantian formation, at least 580 million years ago. A diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma; these are referred to as Vendian biota. Hard-shelled creatures appeared toward the end of that time span, marking the beginning of the Phanerozoic eon. By the middle of the following Cambrian period, a diverse fauna is recorded in the Burgess Shale, including some which may represent stem groups of modern taxa; the increase in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life. While land seems to have been devoid of plants and animals and other microbes formed prokaryotic mats that covered terrestrial areas.
Tracks from an animal with leg like appendages have been found in what was mud 551 million years ago. Evidence of the details of plate motions and other tectonic activity in the Precambrian has been poorly preserved, it is believed that small proto-continents existed prior to 4280 Ma, that most of the Earth's landmasses collected into a single supercontinent around 1130 Ma. The supercontinent, known as Rodinia, broke up around 750 Ma. A number of glacial periods have been identified going as far back as the Huronian epoch 2400–2100 Ma. One of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a "Snowball Earth"; the atmosphere of the early Earth is not well understood. Most geologists believe it was composed of nitrogen, carbon dioxide, other inert gases, was lacking in free oxygen. There is, evidence that an oxygen-rich atmosphere existed since the early Archean. At present, it is still believed that molecular oxygen was not a significant fraction of Earth's atmosphere until after photosynthetic life forms evolved and began to produce it in large quantities as a byproduct of their metabolism.
This radical shift from a chemically inert to an oxidizing atmosphere caused an ecological crisis, sometimes called the oxygen catastrophe. At first, oxygen would have combined with other elements in Earth's crust iron, removing it from the atmosphere. After the supply of oxidizable surfaces ran out, oxygen would have begun to accumulate in the atmosphere, the modern high-oxygen atmosphere would have developed. Evidence for this lies in older rocks that contain massive banded iron formations that were laid down as iron oxides. A terminology has evolved covering the early years of the Earth's existence, as radiometric dating has allowed real dates to be assigned to specific formations and features; the Precambrian is divided into
The Miocene is the first geological epoch of the Neogene Period and extends from about 23.03 to 5.333 million years ago. The Miocene was named by Charles Lyell; the Miocene is followed by the Pliocene. As the earth went from the Oligocene through the Miocene and into the Pliocene, the climate cooled towards a series of ice ages; the Miocene boundaries are not marked by a single distinct global event but consist rather of regionally defined boundaries between the warmer Oligocene and the cooler Pliocene Epoch. The Apes first evolved and diversified during the early Miocene, becoming widespread in the Old World. By the end of this epoch and the start of the following one, the ancestors of humans had split away from the ancestors of the chimpanzees to follow their own evolutionary path during the final Messinian stage of the Miocene; as in the Oligocene before it, grasslands continued to forests to dwindle in extent. In the seas of the Miocene, kelp forests made their first appearance and soon became one of Earth's most productive ecosystems.
The plants and animals of the Miocene were recognizably modern. Mammals and birds were well-established. Whales and kelp spread; the Miocene is of particular interest to geologists and palaeoclimatologists as major phases of the geology of the Himalaya occurred during the Miocene, affecting monsoonal patterns in Asia, which were interlinked with glacial periods in the northern hemisphere. The Miocene faunal stages from youngest to oldest are named according to the International Commission on Stratigraphy: Regionally, other systems are used, based on characteristic land mammals. Of the modern geologic features, only the land bridge between South America and North America was absent, although South America was approaching the western subduction zone in the Pacific Ocean, causing both the rise of the Andes and a southward extension of the Meso-American peninsula. Mountain building took place in western North America and East Asia. Both continental and marine Miocene deposits are common worldwide with marine outcrops common near modern shorelines.
Well studied continental exposures occur in Argentina. India continued creating dramatic new mountain ranges; the Tethys Seaway continued to shrink and disappeared as Africa collided with Eurasia in the Turkish–Arabian region between 19 and 12 Ma. The subsequent uplift of mountains in the western Mediterranean region and a global fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea near the end of the Miocene; the global trend was towards increasing aridity caused by global cooling reducing the ability of the atmosphere to absorb moisture. Uplift of East Africa in the late Miocene was responsible for the shrinking of tropical rain forests in that region, Australia got drier as it entered a zone of low rainfall in the Late Miocene. During the Oligocene and Early Miocene the coast of northern Brazil, south-central Peru, central Chile and large swathes of inland Patagonia were subject to a marine transgression; the transgressions in the west coast of South America is thought to be caused by a regional phenomenon while the rising central segment of the Andes represents an exception.
While there are numerous registers of Oligo-Miocene transgressions around the world it is doubtful that these correlate. It is thought that the Oligo-Miocene transgression in Patagonia could have temporarily linked the Pacific and Atlantic Oceans, as inferred from the findings of marine invertebrate fossils of both Atlantic and Pacific affinity in La Cascada Formation. Connection would have occurred through narrow epicontinental seaways that formed channels in a dissected topography; the Antarctic Plate started to subduct beneath South America 14 million years ago in the Miocene, forming the Chile Triple Junction. At first the Antarctic Plate subducted only in the southernmost tip of Patagonia, meaning that the Chile Triple Junction lay near the Strait of Magellan; as the southern part of Nazca Plate and the Chile Rise became consumed by subduction the more northerly regions of the Antarctic Plate begun to subduct beneath Patagonia so that the Chile Triple Junction advanced to the north over time.
The asthenospheric window associated to the triple junction disturbed previous patterns of mantle convection beneath Patagonia inducing an uplift of ca. 1 km that reversed the Oligocene–Miocene transgression. Climates remained moderately warm, although the slow global cooling that led to the Pleistocene glaciations continued. Although a long-term cooling trend was well underway, there is evidence of a warm period during the Miocene when the global climate rivalled that of the Oligocene; the Miocene warming b
The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period, 298.9 Mya. The name Carboniferous means "coal-bearing" and derives from the Latin words carbō and ferō, was coined by geologists William Conybeare and William Phillips in 1822. Based on a study of the British rock succession, it was the first of the modern'system' names to be employed, reflects the fact that many coal beds were formed globally during that time; the Carboniferous is treated in North America as two geological periods, the earlier Mississippian and the Pennsylvanian. Terrestrial animal life was well established by the Carboniferous period. Amphibians were the dominant land vertebrates, of which one branch would evolve into amniotes, the first terrestrial vertebrates. Arthropods were very common, many were much larger than those of today. Vast swaths of forest covered the land, which would be laid down and become the coal beds characteristic of the Carboniferous stratigraphy evident today.
The atmospheric content of oxygen reached its highest levels in geological history during the period, 35% compared with 21% today, allowing terrestrial invertebrates to evolve to great size. The half of the period experienced glaciations, low sea level, mountain building as the continents collided to form Pangaea. A minor marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred at the end of the period, caused by climate change. In the United States the Carboniferous is broken into Mississippian and Pennsylvanian subperiods; the Mississippian is about twice as long as the Pennsylvanian, but due to the large thickness of coal-bearing deposits with Pennsylvanian ages in Europe and North America, the two subperiods were long thought to have been more or less equal in duration. In Europe the Lower Carboniferous sub-system is known as the Dinantian, comprising the Tournaisian and Visean Series, dated at 362.5-332.9 Ma, the Upper Carboniferous sub-system is known as the Silesian, comprising the Namurian and Stephanian Series, dated at 332.9-298.9 Ma.
The Silesian is contemporaneous with the late Mississippian Serpukhovian plus the Pennsylvanian. In Britain the Dinantian is traditionally known as the Carboniferous Limestone, the Namurian as the Millstone Grit, the Westphalian as the Coal Measures and Pennant Sandstone; the International Commission on Stratigraphy faunal stages from youngest to oldest, together with some of their regional subdivisions, are: A global drop in sea level at the end of the Devonian reversed early in the Carboniferous. There was a drop in south polar temperatures; these conditions had little effect in the deep tropics, where lush swamps to become coal, flourished to within 30 degrees of the northernmost glaciers. Mid-Carboniferous, a drop in sea level precipitated a major marine extinction, one that hit crinoids and ammonites hard; this sea level drop and the associated unconformity in North America separate the Mississippian subperiod from the Pennsylvanian subperiod. This happened about 323 million years ago, at the onset of the Permo-Carboniferous Glaciation.
The Carboniferous was a time of active mountain-building as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America–Europe along the present line of eastern North America; this continental collision resulted in the Hercynian orogeny in Europe, the Alleghenian orogeny in North America. In the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural Mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China, South China continents were still separated from Laurasia; the Late Carboniferous Pangaea was shaped like an "O." There were two major oceans in the Carboniferous—Panthalassa and Paleo-Tethys, inside the "O" in the Carboniferous Pangaea. Other minor oceans were shrinking and closed - Rheic Ocean, the small, shallow Ural Ocean and Proto-Tethys Ocean. Average global temperatures in the Early Carboniferous Period were high: 20 °C.
However, cooling during the Middle Carboniferous reduced average global temperatures to about 12 °C. Lack of growth rings of fossilized trees suggest a lack of seasons of a tropical climate. Glaciations in Gondwana, triggered by Gondwana's southward movement, continued into the Permian and because of the lack of clear markers and breaks, the deposits of this glacial period are referred to as Permo-Carboniferous in age; the cooling and drying of the climate led to the Carboniferous Rainforest Collapse during the late Carboniferous. Tropical rainforests fragmented and were devastated by climate change. Carboniferous rocks in Europe and eastern North America consist of a repeated sequence of limestone, sandstone and coal beds. In North America, the early Carboniferous is marine
The common ostrich, or ostrich, is a species of large flightless bird native to Africa. It is one of two extant species of ostriches, the only living members of the genus Struthio in the ratite order of birds; the other is the Somali ostrich, recognized as a distinct species by BirdLife International in 2014 having been considered a distinctive subspecies of ostrich. The common ostrich shares the order Struthioniformes with the kiwis, emus and cassowaries. However, phylogenetic studies have shown that it is the sister group to all other members of Palaeognathae and thus the flighted tinamous are the sister group to the extinct moa, it is distinctive in its appearance, with a long neck and legs, can run for a long time at a speed of 55 km/h or up to about 70 km/h, the fastest land speed of any bird. The common ostrich is the largest living species of bird and lays the largest eggs of any living bird; the common ostrich's diet consists of plant matter, though it eats invertebrates. It lives in nomadic groups of 5 to 50 birds.
When threatened, the ostrich will either run away. If cornered, it can attack with a kick of its powerful legs. Mating patterns differ by geographical region, but territorial males fight for a harem of two to seven females; the common ostrich is farmed around the world for its feathers, which are decorative and are used as feather dusters. Its skin is used for leather products and its meat is marketed commercially, with its leanness a common marketing point. Common ostriches weigh from 63 to 145 kilograms, or as much as two adult humans; the Masai ostriches of East Africa averaged 115 kg in males and 100 kg in females, while the nominate subspecies, the North African ostrich, 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 with dark brown spots. During the first year of life, chicks grow at about 25 cm per month.
At one year of age, common ostriches weigh 45 kilograms. Their lifespan is up to 40–45 years; the feathers of adult males are black, with white primaries and a white tail. However, the tail of one subspecies is buff. Females and young males are white; the head and neck of both male and female ostriches is nearly bare, with a thin layer of down. The skin of the female's neck and thighs is pinkish grey, while the male's is grey or pink dependent on subspecies; the long neck and legs keep their head up to 2.8 m above the ground, their eyes are said to be the largest of any land vertebrate: 50 mm in diameter. The eyes are shaded from sunlight from above. However, the head and bill are small for the birds' huge size, with the bill measuring 12 to 14.3 cm. Their skin varies in colour depending on the subspecies, with some having light or dark grey skin and others having pinkish or reddish skin; the strong legs of the common ostrich are unfeathered and show bare skin, with the tarsus being covered in scales: red in the male, black in the female.
The tarsus of the common ostrich is the largest of any living bird, measuring 39 to 53 cm in length. The bird has just two toes on each foot, with the nail on the larger, inner toe resembling a hoof; the outer toe has no nail. The reduced number of toes is an adaptation that appears to aid in running, useful for getting away from predators. Common ostriches can cover 3 to 5 m in a single stride; the wings reach a span of about 2 metres, the wing chord measurement of 90 cm is around the same size as for the largest flying birds. The feathers lack the tiny hooks that lock together the smooth external feathers of flying birds, so are soft and fluffy and serve as insulation. Common ostriches can tolerate a wide range of temperatures. In much of their habitat, temperatures vary as much as 40 °C between day, their temperature control relies in part on behavioural thermoregulation. For example, they use their wings to cover the naked skin of the upper legs and flanks to conserve heat, or leave these areas bare to release heat.
The wings function as stabilizers to give better maneuverability when running. Tests have shown that the wings are involved in rapid braking and zigzag maneuvers, they have 50–60 tail feathers, their wings have 16 primary, four alular and 20–23 secondary feathers. The common ostrich's sternum is flat, lacking the keel; the beak is broad, with a rounded tip. Like all ratites, the ostrich has no crop, it lacks a gallbladder, they have three stomachs, the caecum is 71 cm long. Unlike all other living birds, the common ostrich secretes urine separately from faeces. All other birds store the urine and faeces combined in the coprodeum, but the ostrich stores the faeces in the terminal rectum, they have unique pubic bones that are fused to hold their gut. Unlike most birds, the males have a copulatory organ, retractable and 20 cm long, their palate differs from other ratites in that
The Eocene Epoch, lasting from 56 to 33.9 million years ago, is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch; the start of the Eocene is marked by a brief period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C. The end is set at a major extinction event called the Grande Coupure or the Eocene–Oligocene extinction event, which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay; as with other geologic periods, the strata that define the start and end of the epoch are well identified, though their exact dates are uncertain. The name Eocene comes from the Ancient Greek ἠώς and καινός and refers to the "dawn" of modern fauna that appeared during the epoch; the Eocene epoch is conventionally divided into early and late subdivisions.
The corresponding rocks are referred to as lower and upper Eocene. The Ypresian stage constitutes the lower, the Priabonian stage the upper; the Eocene Epoch contained a wide variety of different climate conditions that includes the warmest climate in the Cenozoic Era and ends in an icehouse climate. The evolution of the Eocene climate began with warming after the end of the Palaeocene–Eocene Thermal Maximum at 56 million years ago to a maximum during the Eocene Optimum at around 49 million years ago. During this period of time, little to no ice was present on Earth with a smaller difference in temperature from the equator to the poles. Following the maximum was a descent into an icehouse climate from the Eocene Optimum to the Eocene-Oligocene transition at 34 million years ago. During this decrease ice began to reappear at the poles, the Eocene-Oligocene transition is the period of time where the Antarctic ice sheet began to expand. Greenhouse gases, in particular carbon dioxide and methane, played a significant role during the Eocene in controlling the surface temperature.
The end of the PETM was met with a large sequestration of carbon dioxide in the form of methane clathrate and crude oil at the bottom of the Arctic Ocean, that reduced the atmospheric carbon dioxide. This event was similar in magnitude to the massive release of greenhouse gasses at the beginning of the PETM, it is hypothesized that the sequestration was due to organic carbon burial and weathering of silicates. For the early Eocene there is much discussion; this is due to numerous proxies representing different atmospheric carbon dioxide content. For example, diverse geochemical and paleontological proxies indicate that at the maximum of global warmth the atmospheric carbon dioxide values were at 700–900 ppm while other proxies such as pedogenic carbonate and marine boron isotopes indicate large changes of carbon dioxide of over 2,000 ppm over periods of time of less than 1 million years. Sources for this large influx of carbon dioxide could be attributed to volcanic out-gassing due to North Atlantic rifting or oxidation of methane stored in large reservoirs deposited from the PETM event in the sea floor or wetland environments.
For contrast, today the carbon dioxide levels are at 400 ppm or 0.04%. At about the beginning of the Eocene Epoch the amount of oxygen in the earth's atmosphere more or less doubled. During the early Eocene, methane was another greenhouse gas that had a drastic effect on the climate. In comparison to carbon dioxide, methane has much greater effect on temperature as methane is around 34 times more effective per molecule than carbon dioxide on a 100-year scale. Most of the methane released to the atmosphere during this period of time would have been from wetlands and forests; the atmospheric methane concentration today is 0.000179% or 1.79 ppmv. Due to the warmer climate and sea level rise associated with the early Eocene, more wetlands, more forests, more coal deposits would be available for methane release. Comparing the early Eocene production of methane to current levels of atmospheric methane, the early Eocene would be able to produce triple the amount of current methane production; the warm temperatures during the early Eocene could have increased methane production rates, methane, released into the atmosphere would in turn warm the troposphere, cool the stratosphere, produce water vapor and carbon dioxide through oxidation.
Biogenic production of methane produces carbon dioxide and water vapor along with the methane, as well as yielding infrared radiation. The breakdown of methane in an oxygen atmosphere produces carbon monoxide, water vapor and infrared radiation; the carbon monoxide is not stable so it becomes carbon dioxide and in doing so releases yet more infrared radiation. Water vapor traps more infrared than does carbon dioxide; the middle to late Eocene marks not only the switch from warming to cooling, but the change in carbon dioxide from increasing to decreasing. At the end of the Eocene Optimum, carbon dioxide began decreasing due to increased siliceous plankton productivity and marine carbon burial. At the beginning of the middle Eocene an event that may have triggered or helped with the draw down of carbon dioxide was the Azolla event at around 49 million years ago. With the equable climate during the early Eocene, warm temperatures in the arctic allowed for the growth of azolla, a floating aquatic fern, on the Arctic Ocean.
Compared to current carb
The secretarybird or secretary bird is a large terrestrial bird of prey. Endemic to Africa, it is found in the open grasslands and savannah of the sub-Saharan region. Although a member of the order Accipitriformes, which includes many other diurnal raptors such as kites, hawks and harriers, it is given its own family, Sagittariidae, it appears on the coats of arms of South Africa. In 1769, Arnout Vosmaer was the first European to describe the secretarybird in one of the pamphlets collected as his Regnum Animale, naming it Sagittarius for its gait, thought to resemble an archer's, he mentioned that it was known as the Secretarius by farmers at the Cape of Good Hope who had domesticated it to combat pests around homesteads. In 1779 English illustrator John Frederick Miller described it as secretarybird, it was soon after assigned to its own genus Sagittarius by French naturalist Johann Hermann in his Tabula Affinitatum Animalium, it was not until 1935 that the species was moved to its own family, distinct from all other birds of prey—a classification confirmed by molecular systematics.
Recent cladistic analysis has shown Sagittariidae to be an older branch of the diurnal birds of prey than Accipitridae and Falconidae, but a younger divergence than Cathartidae. Sometimes, the enigmatic bird Eremopezus is classified as an early relative of the secretarybird, though this is uncertain as the bird is only known from a few fragmentary body parts such as the legs; the earliest fossils associated with the family are two species from the genus Pelargopappus. The two species, from the Oligocene and Miocene were not discovered in Africa but France; the feet in these fossils are more like those of the Accipitridae. In spite of their age, it is not thought. Though convergent with the modern secretarybird, the extinct raptor Apatosagittarius is thought to be an accipitrid, its common name is popularly thought to derive from the crest of long quill-like feathers, lending the bird the appearance of a secretary with quill pens tucked behind their ear, as was once common practice. A more recent hypothesis is that "secretary" is borrowed from a French corruption of the Arabic saqr-et-tair or "hunter-bird".
The generic name Sagittarius is Latin for "archer" likening the secretary bird's "quills" to a quiver of arrows, the specific epithet serpentarius recalls the bird's skill as a hunter of reptiles. The secretary bird is recognizable as a large bird with an eagle-like body on crane-like legs which increases the bird’s height to as much as 1.3 m tall. This bird has rounded wings. Height can range from 90 to 137 cm. Total length from 112 to 152 cm and the wingspan is 191–220 cm. Body mass can range from 2.3 to 5 kg with 20 birds from southern Africa found to weigh an average of 4.02 kg. Other attempts to estimate the mean weight range for secretary birds correspondingly lie between 3.5 and 4.2 kg. The tarsus of the secretary bird averages 31 cm and the tail is 57–85 cm, both factor into making them both taller and longer than any other species of raptor since these features are not as long in any other living raptor; the neck is not long, can only be lowered down to the inter-tarsal joint, so birds reaching down to the ground or drinking must stoop to do so.
From a distance or in flight it resembles a crane more than a bird of prey. The tail has two elongated central feathers that extend beyond the feet during flight, as well as long flat plumage creating a posterior crest. Secretary bird flight feathers and thighs are black, while most of the coverts are grey with some being white, it has a large wedge-shaped tail with alternating black banding at its ends. Sexes look similar to one another as the species exhibits little sexual dimorphism, although the male has longer head plumes and tail feathers. Adults have a featherless red-orange face as opposed to the yellow facial skin of the young. Secretary birds are endemic to Sub-Saharan Africa and are non-migratory, though they may follow food sources, their range extends from Mauritania to Somalia and south to the Cape of Good Hope. These birds are found at a variety of elevations, from the coastal plains to the highlands. Secretary birds prefer open grasslands and savannas rather than forests and dense shrubbery which may impede their cursorial existence.
While the birds roost on the local Acacia trees at night, they spend much of the day on the ground, returning to roosting sites just before dark. Unlike most birds of prey, the secretary bird is terrestrial, hunting its prey on foot. Adults hunt in pairs and sometimes as loose familial flocks, stalking through the habitat with long strides. Prey may consist of insects, mammals ranging in size from mice to hares and mongoose, lizards, tortoises, small birds, bird eggs, sometimes dead animals killed in grass or bush fires. Larger herbivores are not hunted, although there are some reports of secretary birds killing young gazelles and cheetah cubs; the importance of snakes in the diet has been exaggerated in the past, although they can be locally important and venomous species such as adders and cobras are among the types of snake preyed upon. Prey is flushed out of tall grass by the birds stomping on the surrounding vegetation, it waits near fires, eating anything it can, trying to escape. They can either catch prey by chasing it and striking with the bill and swallowing