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86-488: The grey heron ( Ardea cinerea ) is a long-legged wading bird of the heron family, Ardeidae, native throughout temperate Europe and Asia , and also parts of Africa . It is resident in much of its range, but some populations from the more northern parts migrate southwards in autumn. A bird of wetland areas, it can be seen around lakes, rivers, ponds, marshes and on the sea coast. It feeds mostly on aquatic creatures which it catches after standing stationary beside or in

172-402: A 155–195 cm (61–77 in) wingspan. The body weight can range from 1.02–2.08 kg (2 lb 4 oz – 4 lb 9 + 1 ⁄ 4  oz). The plumage is largely ashy-grey above, and greyish-white below, with some black on the flanks. Adults have a white head and neck with a broad black supercilium that terminates in the slender, dangling crest, and bluish-black streaks on

258-702: A better sense of smell. A third stage of bird evolution starting with Ornithothoraces (the "bird-chested" avialans) can be associated with the refining of aerodynamics and flight capabilities, and the loss or co-ossification of several skeletal features. Particularly significant are the development of an enlarged, keeled sternum and the alula , and the loss of grasping hands. † Anchiornis † Archaeopteryx † Xiaotingia † Rahonavis † Jeholornis † Jixiangornis † Balaur † Zhongjianornis † Sapeornis † Confuciusornithiformes † Protopteryx † Pengornis Ornithothoraces † Enantiornithes Iris (anatomy) The word "iris"

344-484: A bird arrives at the nest, a greeting ceremony occurs in which each partner raises and lowers its wings and plumes. In continental Europe, and elsewhere, nesting colonies sometimes include nests of the purple heron and other heron species. Courtship involves the male calling from his chosen nesting site. On the arrival of the female, both birds participate in a stretching ceremony, in which each bird extends its neck vertically before bringing it backwards and downwards with

430-609: A dangerous disease of young cyprinids. In addition, large colonies of grey herons can have a significant impact on soil biogeochemistry and vegetation. For example, a heron colony in one study site located near the southern edge of the Republic of Tatarstan on a peninsula formed by the confluence of the Volga , the largest and longest river in Europe, and its largest tributary, the Kama, on

516-446: A dark ring encircling the iris on some individuals, but is a result of the optical properties of the region between the cornea and sclera , not of pigments in the iris. Iris color is a highly complex phenomenon consisting of the combined effects of texture, pigmentation, fibrous tissue, and blood vessels within the iris stroma , which together make up an individual's epigenetic constitution in this context. An organism's "eye color"

602-473: A definition similar to "all theropods closer to birds than to Deinonychus ", with Troodon being sometimes added as a second external specifier in case it is closer to birds than to Deinonychus . Avialae is also occasionally defined as an apomorphy-based clade (that is, one based on physical characteristics). Jacques Gauthier , who named Avialae in 1986, re-defined it in 2001 as all dinosaurs that possessed feathered wings used in flapping flight , and

688-442: A group called Paraves . Some basal members of Deinonychosauria, such as Microraptor , have features which may have enabled them to glide or fly. The most basal deinonychosaurs were very small. This evidence raises the possibility that the ancestor of all paravians may have been arboreal , have been able to glide, or both. Unlike Archaeopteryx and the non-avialan feathered dinosaurs, who primarily ate meat, studies suggest that

774-636: A predator is nearby or a human walks past the colony. The chicks utter loud chattering or ticking noises. The grey heron has an extensive range throughout most of the Palearctic realm . The range of the nominate subspecies A. c. cinerea extends to 70° N in Norway and 66°N in Sweden, but its northerly limit is around 60°N across the rest of Europe and Asia, as far eastwards as the Ural Mountains . To

860-406: A sister group, the order Crocodilia , contain the only living representatives of the reptile clade Archosauria . During the late 1990s, Aves was most commonly 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, and

946-717: A time, sometimes for years, and rarely for life. Other species have breeding systems that are polygynous (one male with many females) or, rarely, polyandrous (one female with many males). 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. 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, meat, and feathers. Songbirds , parrots, and other species are popular as pets. Guano (bird excrement)

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1032-416: Is a loud croaking "fraaank", but a variety of guttural and raucous noises are heard at the breeding colony. The male uses an advertisement call to encourage a female to join him at the nest, and both sexes use various greeting calls after a pair bond has been established. A loud, harsh "schaah" is used by the male in driving other birds from the vicinity of the nest and a soft "gogogo" expresses anxiety, as when

1118-470: Is actually the color of one's iris, the cornea being transparent and the white sclera entirely outside the area of interest. Melanin is yellowish to dark hazel in the stromal pigment cells, and black in the iris pigment epithelium , which lies in a thin but very opaque layer across the back of the iris. Most human irises also show a condensation of the brownish stromal melanin in the thin anterior border layer, which by its position has an overt influence on

1204-466: Is closely related and similar to the North American great blue heron ( Ardea herodias ), which differs in being larger, and having chestnut-brown flanks and thighs; and to the cocoi heron ( Ardea cocoi ) from South America, with which it forms a superspecies. Some authorities believe that the subspecies A. c. monicae should be considered a separate species. It has been known to hybridise with

1290-504: Is derived from the Greek word for " rainbow ", also its goddess plus messenger of the gods in the Iliad , because of the many colours of this eye part. The iris consists of two layers: the front pigmented fibrovascular layer known as a stroma and, behind the stroma, pigmented epithelial cells. The stroma is connected to a sphincter muscle ( sphincter pupillae ), which contracts

1376-429: Is harvested for use as a fertiliser. Birds figure throughout human culture. About 120 to 130 species have become extinct due to human activity since the 17th century, and 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

1462-404: Is located on the inner border. The back surface is covered by a heavily pigmented epithelial layer that is two cells thick (the iris pigment epithelium), but the front surface has no epithelium. This anterior surface projects as the dilator muscles. The high pigment content blocks light from passing through the iris to the retina, restricting it to the pupil. The outer edge of the iris, known as

1548-503: Is not considered a direct ancestor of birds, though it is possibly closely related to the true ancestor. Over 40% of key traits found in modern birds evolved during the 60 million year transition from the earliest bird-line archosaurs to the first maniraptoromorphs , i.e. the first dinosaurs closer to living birds than to Tyrannosaurus rex . The loss of osteoderms otherwise common in archosaurs and acquisition of primitive feathers might have occurred early during this phase. After

1634-415: Is seen; if not, they will remain blue or gray. All the contributing factors towards eye color and its variation are not fully understood. Autosomal recessive/dominant traits in iris color are inherent in other species, but coloration can follow a different pattern. Heterochromia (also known as a heterochromia iridis or heterochromia iridum) is an ocular condition in which one iris is a different color from

1720-516: Is synonymous to Avifilopluma. † Scansoriopterygidae † Eosinopteryx † Jinfengopteryx † Aurornis † Dromaeosauridae † Troodontidae Avialae Based on fossil and biological evidence, most scientists accept that birds are a specialised subgroup of theropod dinosaurs and, more specifically, members of Maniraptora , a group of theropods which includes dromaeosaurids and oviraptorosaurs , among others. As scientists have discovered more theropods closely related to birds,

1806-535: Is used by many scientists including adherents to the PhyloCode . 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 , and assigning them, instead, to the broader group Avialae, on the principle that a clade based on extant species should be limited to those extant species and their closest extinct relatives. Gauthier and de Queiroz identified four different definitions for

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1892-411: Is used year after year until blown down; it starts as a small platform of sticks but expands into a bulky nest as more material is added in subsequent years. It may be lined with smaller twigs, strands of root or dead grasses; in reed beds, it is built from dead reeds. The male usually collects the material, while the female constructs the nest. Breeding activities take place between February and June. When

1978-611: The Aldabra Islands , the subspecies A. c. firasa is found, while the subspecies A. c. monicae is restricted to Mauritania and offshore islands. Over much of its range, the grey heron is resident, but birds from the more northerly parts of Europe migrate southwards, some remaining in Central and Southern Europe, others travelling on to Africa south of the Sahara Desert. The grey heron is also known to be vagrant in

2064-626: The Netherlands , it has established itself over the past decades in great numbers in urban environments. In cities such as Amsterdam , they are ever present and well adapted to modern city life. They hunt as usual, but also visit street markets and snack bars. Some individuals make use of people feeding them at their homes or share the catch of recreational fishermen. Similar behaviour on a smaller scale has been reported in Ireland. Garden ponds stocked with ornamental fish are attractive to herons, and

2150-858: The Pyrenees is thought to have been killed by an otter . The bird may have been weakened by harsh winter weather causing scarcity of its prey. A study performed by Sitko and Heneberg in the Czech Republic between 1962 and 2013 suggested that Central European grey herons host 29 species of parasitic worms . The dominant species consisted of Apharyngostrigea cornu (67% prevalence), Posthodiplostomum cuticola (41% prevalence), Echinochasmus beleocephalus (39% prevalence), Uroproctepisthmium bursicola (36% prevalence), Neogryporhynchus cheilancristrotus (31% prevalence), Desmidocercella numidica (29% prevalence), and Bilharziella polonica (5% prevalence). Juvenile grey herons were shown to host fewer species, but

2236-669: The Tiaojishan Formation of China, which has been dated to the late Jurassic period ( Oxfordian stage), about 160 million years ago. The avialan species from this time period include Anchiornis huxleyi , Xiaotingia zhengi , and Aurornis xui . The well-known probable early avialan, Archaeopteryx , dates from slightly later Jurassic rocks (about 155 million years old) from Germany . Many of these early avialans shared unusual anatomical features that may be ancestral to modern birds but were later lost during bird evolution. These features include enlarged claws on

2322-478: The deity Bennu was depicted as a heron in New Kingdom artwork. In Ancient Rome , the heron was a bird of divination . Roast heron was once a specially prized dish; when George Neville became Archbishop of York in 1465, 400 herons were served to the guests. Grey herons belong to the subfamily Ardeinae , along with the majority of extant species, which are known as the "typical herons". The grey heron

2408-406: The depth of field . Very few humans possess the ability to exert direct voluntary control over their iris muscles, which grants them the ability to dilate and constrict their pupils on command. However, there is no clear purpose or advantage to this. The iris is usually strongly pigmented , with the color typically ranging between brown, hazel, green, gray, and blue. Occasionally, the color of

2494-417: The great egret ( Ardea alba ), the little egret ( Egretta garzetta ), the great blue heron and the purple heron ( Ardea purpurea ). The Australian white-faced heron is often incorrectly called a grey heron. In Ireland, the grey heron is often colloquially called a "crane". The grey heron is a large bird, standing up to 100 cm (40 in) tall and measuring 84–102 cm (33–40 in) long with

2580-575: The only known living dinosaurs . Likewise, birds are considered reptiles in the modern cladistic sense of the term, and their closest living relatives are the crocodilians . Birds are descendants of the primitive avialans (whose members include Archaeopteryx ) which first appeared during the Late Jurassic . According to recent estimates, modern birds ( Neornithes ) evolved in the Late Cretaceous and diversified dramatically around

2666-433: The 5.5 cm (2.2 in) bee hummingbird to the 2.8 m (9 ft 2 in) common ostrich . There are over 11,000 living species and they are split into 44 orders . More than half are passerine or "perching" birds. Birds have wings whose development varies according to species; the only known groups without wings are the extinct moa and elephant birds . Wings, which are modified forelimbs , gave birds

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2752-543: The Caribbean, Bermuda, Iceland, Greenland, the Aleutian Islands, and Newfoundland, with a few confirmed sightings in other parts of North America including Nova Scotia and Nantucket. Within its range, the grey heron can be found anywhere with suitable watery habitat that can supply its food. The water body must be either shallow enough, or have a shelving margin in it, so that it can wade. Although most common in

2838-533: The First was dubbed dikoros (having two irises) for his patent heterochromia since his right iris had a darker color than the left one. In contrast, heterochromia and variegated iris patterns are common in veterinary practice. Siberian Husky dogs show heterochromia, possibly analogous to the genetically determined Waardenburg syndrome of humans. Some white cat fancies (e.g., white Turkish Angora or white Turkish Van cats) may show striking heterochromia, with

2924-480: The ability to fly, although further evolution has led to the loss of flight in some birds , including ratites , penguins , and diverse endemic island 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 further evolved for swimming. The study of birds is called ornithology . Birds are feathered theropod dinosaurs and constitute

3010-443: The anterior ciliary body provide a secondary pathway for aqueous humour to drain from the eye. The iris is divided into two major regions: The collarette is the thickest region of the iris, separating the pupillary portion from the ciliary portion. The collarette is a vestige of the coating of the embryonic pupil. It is typically defined as the region where the sphincter muscle and dilator muscle overlap. Radial ridges extend from

3096-428: The appearance of Maniraptoromorpha, the next 40 million years marked a continuous reduction of body size and the accumulation of neotenic (juvenile-like) characteristics. Hypercarnivory became increasingly less common while braincases enlarged and forelimbs became longer. The integument evolved into complex, pennaceous feathers . The oldest known paravian (and probably the earliest avialan) fossils come from

3182-430: The average life expectancy in the wild is about 5 years. Only about a third of juveniles survive into their second year, many falling victim to predation. On May 24, 1990, on the proposal of Marek Vahula, the nesting colony of Vandu village of Kadrina municipality (up to 125 nesting trees) was taken under protection in the 1st place. In the spring-winter of 2001, all suitable nesting trees were cut down there in defiance of

3268-510: The banks of the smaller river Myosha (a tributary of the Kama); after settling around 2006, it expanded for 15 years, leading to the intensive deposition of nutrients with faeces, food remains and feathers thereby considerably altering the local soil biogeochemistry. Thus, lower pH levels around 4.5, 10- and 2-fold higher concentrations of phosphorus and nitrogen, as well as 1.2-fold discrepancies in K, Li, Mn, Zn and Co, respectively, compared to

3354-437: The bill remaining vertical, simultaneously flexing its legs, before returning to its normal stance. The snapping ceremony is another behaviour where the neck is extended forward, the head is lowered to the level of the feet, and the mandibles are vigorously snapped together. This may be repeated 20-40 times. When the pairing is settled, the birds may caress each other by attending to the other bird's plumage. The male may then offer

3440-509: The birds that descended from them. Despite being currently one of the most widely used, the crown-group definition of Aves has been criticised by some researchers. Lee and Spencer (1997) argued that, contrary to what Gauthier defended, this definition would not increase the stability of the clade and the exact content of Aves will always be uncertain because any defined clade (either crown or not) will have few synapomorphies distinguishing it from its closest relatives. Their alternative definition

3526-619: The blood vessels, collagen in the vessel and stroma) is the most important element. Rayleigh scattering and Tyndall scattering , (which also happen in the sky) and diffraction also occur. Raman scattering , and constructive interference , as in the feathers of birds, do not contribute to the color of the eye, but interference phenomena are important in the brilliantly colored iris pigment cells ( iridophores ) in many animals. Interference effects can occur at both molecular and light-microscopic scales, and are often associated (in melanin-bearing cells) with quasicrystalline formations, which enhance

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3612-399: The character of a satirical TV show . Bird Birds are a group of warm-blooded vertebrates constituting the class Aves ( Latin: [ˈaveːs] ), characterised by feathers , toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart , and a strong yet lightweight skeleton . Birds live worldwide and range in size from

3698-486: The chitinous remains of insects. The main hunting periods are around dawn and dusk, but it is also active at other times of the day. At night it roosts in trees or on cliffs, where it tends to be gregarious. This species breeds in colonies known as heronries, usually in high trees close to lakes, the seashore, or other wetlands. Other sites are sometimes chosen, and these include low trees and bushes, bramble patches, reed beds , heather clumps and cliff ledges. The same nest

3784-585: The conservation regulations. Driven by this, the nationwide heron protection and research project "The Heron Seeker" was brought to life. In seven years (2007-2014) all nesting colonies and feeding grounds in Estonia were mapped. The project's final result was the English-language E-book: "Heron Seeker`s book" Tallinn, 2024. (ISBN 978-9916-9943-3-7). Grey herons have the ability to live in cities where habitats and nesting space are available. In

3870-665: The earliest members of Aves, is removed from this group, becoming a non-avian dinosaur instead. These proposals have been adopted by many researchers in the field of palaeontology and bird evolution , though the exact definitions applied have been inconsistent. Avialae, initially proposed to replace the traditional fossil content of Aves, is often used synonymously with the vernacular term "bird" by these researchers. † Coelurus † Ornitholestes † Ornithomimosauria † Alvarezsauridae † Oviraptorosauria   Paraves Most researchers define Avialae as branch-based clade, though definitions vary. Many authors have used

3956-427: The easy prey may provide young birds with a learning opportunity on how to hunt. Herons have been observed visiting water enclosures in zoos, such as spaces for penguins , otters , pelicans , and seals , and taking food meant for the animals on display. In a variety of sources, one can find a common statement that grey herons, by eating large quantities of fish, is a significant pest of fisheries, causing damage to

4042-516: The female a stick, which she incorporates into the nest. At this, the male becomes excited, further preening the female, and copulation takes place. The clutch of eggs usually numbers three to five, though as few as two and as many as seven eggs have been recorded. The eggs have a matt surface and are greenish-blue, averaging 60 mm × 43 mm ( 2 + 3 ⁄ 8  in ×  1 + 11 ⁄ 16  in). The eggs are normally laid at two-day intervals and incubation usually starts after

4128-451: The first avialans were omnivores . The Late Jurassic Archaeopteryx is well known as one of the first transitional fossils to be found, and it provided support for the theory of evolution in the late 19th century. Archaeopteryx was the first fossil to display both clearly traditional reptilian characteristics—teeth, clawed fingers, and a long, lizard-like tail—as well as wings with flight feathers similar to those of modern birds. It

4214-494: The first or second egg has been laid. Both birds take part in incubation and the period lasts about 25 days. Both parents bring food for the young. At first, the chicks seize the adult's bill from the side and extract regurgitated food from it. Later, the adult disgorges the food at the nest and the chicks squabble for possession. They fledge at 7-8 weeks. Usually, a single brood is raised each year, but two broods have been recorded. The oldest recorded bird lived for 23 years, but

4300-443: The front of the neck. The scapular feathers and the feathers at the base of the neck are somewhat elongated. Immature birds lack the dark stripe on the head and are generally duller in appearance than adults, with a grey head and neck, and a small, dark grey crest. The pinkish-yellow beak is long, straight, and powerful, and is brighter in color in breeding adults. The iris is yellow and the legs are brown and very long. The main call

4386-422: The grey heron does cause significant damage to fisheries, but the damage caused by eating valuable fish species is balanced by the fact that it eats a large number of fish affected by ligulosis. The undoubted benefit of the heron is also expressed in the fact that it eats a lot of harmful insects. However, in some places, grey herons can serve as a breeding ground for the so-called ink sickness, or postodiplostomosis,

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4472-606: The guests. Young birds were still being shot and eaten in Romney Marsh in 1896. Two grey herons feature in a stained-glass window of the church in Selborne , Hampshire . The English surnames Earnshaw, Hernshaw, Herne, and Heron all derive from the heron, the suffix -shaw meaning a wood , referring to a place where herons nested. The bird is common in the Maldives under the name of Maakana and has given its name to

4558-730: The heron caught fish in the dark, which made it difficult to fight it). It was undoubtedly noted that grey herons, especially in the post-nesting period, when forage migrations begin, gather in significant numbers on fish ponds and then eat many juveniles of cultivated fish species. In the Kuban delta , the share of valuable, specially cultivated species was significant in the hunting of the grey heron, of which 84% were carp, 12% were white carp, and  4%  were Bighead carp . According to studies at fish ponds in Upper Lusatia in Germany ,

4644-689: The heron's long bill. It has also been observed catching and killing juvenile birds such as ducklings , and occasionally takes birds up to the size of a water rail or white-throated rail . Small mammals such as water voles , rats , stoats and young rabbits are additionally caught. Prey items vary in size from 1 cm-long fish and invertebrates, weighing less than 1g, to 30 cm-long carps and 57cm eels. While chicks tend to have smaller prey, individual prey caught by fully-grown Grey Herons commonly exceed 100g in weight and occasionally exceed 500g. One paper reports that an adult heron managed to catch and swallow sea trout weighing 680g. It may stand motionless in

4730-406: The heronry and chase each other, undertake aerial manoeuvres or swoop down towards the ground. The birds often perch in trees, but spend much time on the ground, striding about or standing still for long periods with an upright stance, often on a single leg. Grey herons are apex predators in their aquatic ecosystem. Fish , amphibians , crustaceans , and insects are caught in shallow water with

4816-504: The intensity of infection was higher in the juveniles than in the adult herons. Of the digenean flatworms found in Central European grey herons, 52% of the species likely infected their definitive hosts outside Central Europe itself, in the premigratory, migratory, or wintering quarters, despite the fact that a substantial proportion of grey herons do not migrate to the south. Bennu , an ancient Egyptian deity associated with

4902-405: The iris is due to a lack of pigmentation, as in the pinkish-white of oculocutaneous albinism , or to obscuration of its pigment by blood vessels, as in the red of an abnormally vascularised iris. Despite the wide range of colors, the only pigment that contributes substantially to normal iris color is the dark pigment melanin . The quantity of melanin pigment in the iris is one factor in determining

4988-419: The layers of the iris are: The stroma and the anterior border layer of the iris are derived from the neural crest , and behind the stroma of the iris, the sphincter pupillae and dilator pupillae muscles, as well as the iris epithelium, develop from optic cup neuroectoderm. The iris controls the size of the pupil by means of contracting the iris sphincter muscle and/or the iris dilator muscle . The size of

5074-425: The legs are brown. The birds breed colonially in spring in heronries , usually building their nests high in trees. A clutch of usually three to five bluish-green eggs is laid. Both birds incubate the eggs for around 25 days, and then both feed the chicks, which fledge when 7-8 weeks old. Many juveniles do not survive their first winter, but if they do, they can expect to live for about 5 years. In Ancient Egypt ,

5160-469: The lowlands, it also occurs in mountain tarns, lakes, reservoirs, rivers, marshes, ponds, ditches, flooded areas, coastal lagoons, estuaries, and the sea shore. It sometimes forages away from water in pasture, and it has been recorded in desert areas, hunting for beetles and lizards. Breeding colonies are usually near feeding areas, but exceptionally may be up to eight kilometres (five miles) away, and birds sometimes forage as much as 20 km (12 mi) from

5246-452: The most common pattern being one uniformly blue, the other copper, orange, yellow, or green. Striking variation within the same iris is also common in some animals, and is the norm in some species. Several herding breeds, particularly those with a blue merle coat color (such as Australian Shepherds and Border Collies ) may show well-defined blue areas within a brown iris, as well as separate blue and darker eyes. Some horses (usually within

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5332-460: The nesting site. The grey heron has a slow flight, with its long neck retracted in an S-shape. This is characteristic of herons and bitterns , and distinguishes them from storks , cranes , and spoonbills , which extend their necks. It flies with slow wing-beats and sometimes glides for short distances. It sometimes soars, circling to considerable heights, but not as often as the stork. In spring, and occasionally in autumn, birds may soar high above

5418-446: The optical effects. Interference is recognised by characteristic dependence of color on the angle of view, as seen in eyespots of some butterfly wings , although the chemical components remain the same. White babies are usually born blue-eyed since no pigment is in the stroma, and their eyes appear blue due to scattering and selective absorption from the posterior epithelium. If melanin is deposited substantially, brown or black color

5504-410: The other iris (complete heterochromia), or where the part of one iris is a different color from the remainder (partial heterochromia or sectoral heterochromia). Uncommon in humans, it is often an indicator of ocular disease, such as chronic iritis or diffuse iris melanoma, but may also occur as a normal variant. Sectors or patches of strikingly different colors in the same iris are less common. Anastasius

5590-414: The other stromal components. Sometimes, lipofuscin , a yellow "wear and tear" pigment, also enters into the visible eye color, especially in aged or diseased green eyes. The optical mechanisms by which the nonpigmented stromal components influence eye color are complex, and many erroneous statements exist in the literature. Simple selective absorption and reflection by biological molecules ( hemoglobin in

5676-402: The outermost half) can be seen in the evolution of maniraptoromorphs, and this process culminated in the appearance of the pygostyle , an ossification of fused tail vertebrae. In the late Cretaceous, about 100 million years ago, the ancestors of all modern birds evolved a more open pelvis, allowing them to lay larger eggs compared to body size. Around 95 million years ago, they evolved

5762-510: The overall color. The degree of dispersion of the melanin, which is in subcellular bundles called melanosomes , has some influence on the observed color, but melanosomes in the iris of humans and other vertebrates are not mobile, and the degree of pigment dispersion cannot be reversed. Abnormal clumping of melanosomes does occur in disease and may lead to irreversible changes in iris color (see heterochromia , below). Colors other than brown or black are due to selective reflection and absorption from

5848-455: The periphery to the pupillary zone, to supply the iris with blood vessels. The root of the iris is the thinnest and most peripheral. The muscle cells of the iris are smooth muscle in mammals and amphibians, but are striated muscle in reptiles (including birds). Many fish have neither, and, as a result, their irises are unable to dilate and contract, so that the pupil always remains of a fixed size. From anterior (front) to posterior (back),

5934-413: The phenotypic eye color of an organism. Structurally, this huge molecule is only slightly different from its equivalent found in skin and hair . Iris color is due to variable amounts of eumelanin (brown/black melanins) and pheomelanin (red/yellow melanins) produced by melanocytes. More of the former is found in brown-eyed people and of the latter in blue- and green-eyed people. The limbal ring appears as

6020-620: The population of valuable fish both in natural reservoirs and in ponds intended for the cultivation of cultivated fish species. For example, in the 1970s, major Soviet experts considered the grey heron to be a harmful species, for example, for fish breeding reservoirs in Ukraine . In particular, it was established that in Ukraine and in general in the southern regions of the USSR ,  carp and mullet suffered from heron farms (there, in addition,

6106-536: The previously clear distinction between non-birds and birds has become blurred. By the 2000s, discoveries in the Liaoning Province of northeast China, which demonstrated many small theropod feathered dinosaurs , contributed to this ambiguity. The consensus view in contemporary palaeontology is that the flying theropods, or avialans , are the closest relatives of the deinonychosaurs , which include dromaeosaurids and troodontids . Together, these form

6192-408: The pupil in a circular motion, and a set of dilator muscles ( dilator pupillae ), which pull the iris radially to enlarge the pupil, pulling it in folds. The sphincter pupillae is the opposing muscle of the dilator pupillae. The pupil's diameter, and thus the inner border of the iris, changes size when constricting or dilating. The outer border of the iris does not change size. The constricting muscle

6278-401: The pupils is dependent on many factors (including light, emotional state, cognitive load, arousal, stimulation), and can range from less than 2 mm in diameter, to as large as 9 mm in diameter. However, there is considerable variation in maximal pupil diameter by individual humans, and decreases with age. The irises also contract the pupils when accommodation is initiated, to increase

6364-445: The root, is attached to the sclera and the anterior ciliary body . The iris and ciliary body together are known as the anterior uvea . Just in front of the root of the iris is the region referred to as the trabecular meshwork , through which the aqueous humour constantly drains out of the eye, with the result that diseases of the iris often have important effects on intraocular pressure and indirectly on vision. The iris along with

6450-452: The same biological name "Aves", which is a problem. The authors 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. They assigned other names to the other groups.   Lizards & snakes   Turtles   Crocodiles   Birds Under the fourth definition Archaeopteryx , traditionally considered one of

6536-551: The second toe which may have been held clear of the ground in life, and long feathers or "hind wings" covering the hind limbs and feet, which may have been used in aerial maneuvering. Avialans diversified into a wide variety of forms during the Cretaceous period. Many groups retained primitive characteristics , such as clawed wings and teeth, though the latter were lost independently in a number of avialan groups, including modern birds (Aves). Increasingly stiff tails (especially

6622-402: The shallows, or on a rock or sandbank beside the water, waiting for prey to come within striking distance. Alternatively, it moves slowly and stealthily through the water with its body less upright than when at rest and its neck curved in an "S". It is then able to straighten its neck and strike with its bill very quickly. Small fish are swallowed head first, and larger prey and eels are carried to

6708-468: The shore where they are subdued by being beaten on the ground or stabbed by the bill. They are then swallowed or have hunks of flesh torn off. For prey such as small mammals and birds or ducklings, the prey is held by the neck and either drowned, suffocated, has its neck snapped with the heron's beak, or is bludgeoned against the ground or a nearby rock, before being swallowed whole. The bird regurgitates pellets of indigestible material such as fur, bones, and

6794-781: The south, its range extends to northern Spain, France, central Italy, the Balkans, the Caucasus, Iraq, Iran, India, The Maldives and Myanmar (Burma). It is also present in Africa south of the Sahara Desert , the Canary Islands , Morocco, Algeria, Tunisia, and many of the Mediterranean Islands. It is replaced by A. c. jouyi in eastern Siberia, Mongolia, eastern China, Hainan, Japan, and Taiwan. In Madagascar and

6880-487: The sun, creation, and rebirth, was depicted as a heron in New Kingdom artwork. In ancient Rome , the heron was a bird of divination that gave an augury (sign of a coming event) by its call, like the raven, stork, and owl. Roast heron was once a specially prized dish in Britain for special occasions such as state banquets. For the appointment of George Neville as Archbishop of York in 1465, 400 herons were served to

6966-403: The surrounding control forest area could be observed. Being large birds with powerful beaks, grey herons have few predators as adults, but white-tailed eagles and more rarely Eurasian goshawks will take them as prey. The eggs and young are more vulnerable; the adult birds do not usually leave the nest unattended, but may be lured away by marauding crows or kites . A dead grey heron found in

7052-600: The time of the Cretaceous–Paleogene extinction event 66 million years ago, which killed off the pterosaurs and all non- ornithuran dinosaurs. Many social species preserve knowledge across generations ( culture ). Birds are social, communicating with visual signals, calls, and songs , and participating in such behaviour as cooperative breeding and hunting, flocking , and mobbing of predators. The vast majority of bird species are socially (but not necessarily sexually) monogamous , usually for one breeding season at

7138-417: The water, or stalking its prey through the shallows. Standing up to 1 metre (3 ft 3 in) tall, adults weigh from 1 to 2 kg (2 to 4 lb). They have a white head and neck with a broad black stripe that extends from the eye to the black crest. The body and wings are grey above and the underparts are greyish-white, with some black on the flanks. The long, sharply pointed beak is pinkish-yellow and

7224-446: The white, spotted, palomino, or cremello groups of breeds) may show amber, brown, white and blue all within the same eye, without any sign of eye disease. One eye with a white or bluish-white iris is also known as a "walleye". Iridology (also known as iridodiagnosis) is an alternative medicine technique whose proponents believe that patterns, colors, and other characteristics of the iris can be examined to determine information about

7310-522: Was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae . He placed it with the cattle egret and the great egret in the genus Ardea and coined the binomial name Ardea cinerea . The scientific name comes from the Latin ardea meaning "heron" and cinereus meaning "ash-grey" or "ash-coloured". Four subspecies are recognised: It

7396-466: 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 clade Theropoda as an infraclass or a subclass, more recently a subclass. Aves and

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