42-411: A bird is a feathered, winged, bipedal, warm-blooded, egg-laying, vertebrate. Bird , BIRD , or the bird may also refer to: 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
84-486: A nightingale or marsh warbler . However, although many songbirds have songs that are pleasant to the human ear, this is not invariably the case. Many members of the crow family ( Corvidae ) communicate with croaks or screeches, which sound harsh to humans. Even these, however, have a song of sorts, a softer twitter that is given between courting partners. And even though some parrots (which are not songbirds) can be taught to repeat human speech, vocal mimicry among birds
126-998: 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 Songbird Menuridae Atrichornithidae Climacteridae Ptilonorhynchidae Maluridae Meliphagidae Dasyornithidae Pardalotidae Acanthizidae Pomatostomidae Orthonychidae Cnemophilidae Melanocharitidae Callaeidae Notiomystidae Corvides Passerida See text A songbird
168-466: A bird's song. As a result, songs can vary even within a single species. Many believe that song repertoire and cognition have a direct relationship. However, a study published in 2013 has shown that cognitive abilities may not all be directly related to the song repertoire of a songbird. Specifically, spatial learning is said to have an inverse relationship with song repertoire. So for example, this would be an individual who does not migrate as far as others in
210-473: 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
252-529: A familiar perch, other species common to grasslands will sing a familiar song each time they fly. Currently, there have been numerous studies involving songbird repertoires, unfortunately, there has not yet been a concrete evidence to confirm that every songbird species prefers larger repertoires. A conclusion can be made that it can vary between species on whether a larger repertoire is connected to better fitness. With this conclusion, it can be inferred that evolution via natural selection, or sexual selection, favors
294-442: 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
336-424: A highly developed vocal organ, the syrinx , that enables their sonorous activity. This organ, also known as a song box, can be found where the windpipe meets diverging bronchial tubes which lead to the lungs. The organ is a solid, bony structure lined with a film of membranes which air passes through as the songbird calls. While the song boxes of songbirds vary in size and intricacy, this does not necessarily determine
378-406: 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
420-424: A strong yet lightweight skeleton . Birds live worldwide and range in size from 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
462-717: 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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#1732783213753504-425: Is a bird belonging to the suborder Passeri of the perching birds ( Passeriformes ). Another name that is sometimes seen as the scientific or vernacular name is Oscines , from Latin oscen , "songbird". The Passeriformes contains 5,000 or so species found all over the world, in which the vocal organ typically is developed in such a way as to produce a diverse and elaborate bird song . Songbirds form one of
546-465: Is a highly diverse lineage, uniting over one-third of all bird species to include (in 2015) 3,885 species ). These are divided into three major superfamilies (though not exactly corresponding to the Sibley-Ahlquist arrangement), in addition to some minor lineages. In contrast, Sibley & Alquist's "Corvida" is a phylogenetic grade and an artefact of the phenetic methodology. The bulk of
588-435: Is a significant realm of study as song abilities are continuously evolving. Males often sing to assert their dominance over other males in competition for a female, sometimes in lieu of a combative episode, and to arouse the female by announcing a readiness to mate. Though less frequent, females have also been known to sing occasionally a duet with a mate as an affirmation of their partnership. While some will sing their song from
630-550: Is almost completely restricted to songbirds, some of which (such as the lyrebirds or the aptly named mockingbirds ) excel in imitating the sounds of other birds or even environmental noises. The birds from higher altitudes have evolved thicker downs (also known as jackets) to protect themselves from colder temperatures. Their feathers have outer and inner portions, with the lower down being fluffier and warmer to provide increased warmth. Sexual selection can be broken down into several different studies regarding different aspects of
672-540: Is called ornithology . Birds are feathered theropod dinosaurs and constitute 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
714-429: 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
756-503: 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
798-516: 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,
840-535: 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
882-523: The Acanthisitti of New Zealand , of which only two species remain alive today. Recent estimates indicate that songbirds originated 50 million years ago. The distribution of their basal lineages suggest that their origin and initial diversification occurred exclusively in the Australian continent and only about 40 million years ago, oscines started to colonize Eurasia , Africa , and eventually
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#1732783213753924-457: The Americas . The song in this clade is essentially territorial, because it communicates the identity and whereabouts of an individual to other birds, and also signals sexual intentions. Sexual selection among songbirds is highly based on mimetic vocalization. Female preference has shown in some populations to be based on the extent of a male's song repertoire. The larger a male's repertoire,
966-722: The Late Cretaceous and diversified dramatically around 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
1008-669: 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
1050-866: The "Corvida" make up the large clade Corvides (812 species as of 2015 ), which is a sister group to the Passerida. The remaining 15 oscine families (343 species in 2015 ) form a series of basally branching sister groups to the Corvoid - Passerid clade. All of these groups, which form at least six successively branching basal clades, are found exclusively or predominantly in Australasia. Australian endemics are also prominent among basal lineages in both Corvoids and Passerids, suggesting that songbirds originated and diverged in Australia. Scrubbirds and lyrebirds, of which there are just two species of each, represent
1092-419: The ability to retain larger repertoires for these certain species as it leads to higher reproductive success. During times of courtship, it is said that male songbirds increase their repertoire by mimicking other species songs. The better the mimicking ability, retaining ability, and the quantity of other species mimicked has been proven to have a positive relationship with mating success. Female preferences cause
1134-428: 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
1176-509: 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
1218-411: The constant improvement of accuracy and presentation of the copied songs. Another theory known as the "song-sharing hypothesis" suggests that females prefer simpler, more homogenous songs that signal a male of familiar territory. As birdsong can be broken into regional dialects through this process of mimicry, the foreign song of a newcomer suggests the lack of territorial possession. This can be costly in
1260-665: 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
1302-483: The extinct moa and elephant birds . Wings, which are modified forelimbs , gave birds 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
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1344-451: 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
1386-432: The more females a male individual attracts. It is not to be confused with bird calls that are used for alarms and contact and are especially important in birds that feed or migrate in flocks. While almost all living birds give calls of some sort, well-developed songs are only given by a few lineages outside the songbirds. And still, not all songbirds proffer a call that is distinctly melodious. Songbirds do, however, possess
1428-402: 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
1470-536: 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
1512-452: 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
1554-551: 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
1596-413: The songbird's ability to voice their song. Researchers believe this has more to do with the length of the windpipe. Other birds (especially non-passeriforms) sometimes have songs to attract mates or hold territory, but these are usually simple and repetitive, lacking the variety of many oscine songs. The monotonous repetition of the common cuckoo or little crake can be contrasted with the variety of
1638-636: The species but has a better song repertoire. This suggests an evolutionary trade-off between possible alleles. With natural selection choosing traits best fit for reproductive success, there could be a trade-off in either direction depending on which trait would produce a higher fitness at that time period. Song repertoire can be attributed to male songbirds as it is one of the main mechanisms of courtship. Song repertoires differ from male individual to male individual and species to species. Some species may typically have large repertoires while others may have significantly smaller ones. Mate choice in female songbirds
1680-537: The two major lineages of extant perching birds (~4,000 species), the other being the Tyranni (~1,000 species), which are most diverse in the Neotropics and absent from many parts of the world. The Tyranni have a simpler syrinx musculature, and while their vocalizations are often just as complex and striking as those of songbirds, they are altogether more mechanical sounding. There is a third perching bird lineage,
1722-531: The wake of territorial conflicts between disparate songbird populations and may compel a female to prefer a male spouting a familiar song of the area. Sibley and Alquist divided songbirds into two " parvorders ", Corvida and Passerida (standard taxonomic practice would rank these as infraorders ), distributed in Australo-Papua and Eurasia respectively. Subsequent molecular studies, however, show this treatment to be somewhat erroneous. Passerida
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1764-466: 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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