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79-455: Stilt is a common name for several species of birds in the family Recurvirostridae , which also includes those known as avocets . They are found in brackish or saline wetlands in warm or hot climates. They have extremely long legs, hence the group name, and long thin bills. Stilts typically feed on aquatic insects and other small creatures and nest on the ground surface in loose colonies. Most sources recognize 6 species in 2 genera, although

158-729: 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 Bird vocalization The distinction between songs and calls

237-477: A cue to conspecific eavesdroppers. In black-throated blue warblers , males that have bred and reproduced successfully sing to their offspring to influence their vocal development, while males that have failed to reproduce usually abandon the nests and stay silent. The post-breeding song therefore inadvertently informs the unsuccessful males of particular habitats that have a higher likelihood of reproductive success. The social communication by vocalization provides

316-473: 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

395-473: A female bird may select males based on the quality of their songs and the size of their song repertoire. The second principal function of bird song is territory defense. Territorial birds will interact with each other using song to negotiate territory boundaries. Since song may be a reliable indicator of quality, individuals may be able to discern the quality of rivals and prevent an energetically costly fight. In birds with song repertoires, individuals may share

474-442: 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

553-399: A less aggressive act than song-type matching. Song complexity is also linked to male territorial defense, with more complex songs being perceived as a greater territorial threat. Birds communicate alarm through vocalizations and movements that are specific to the threat, and bird alarms can be understood by other animal species, including other birds, in order to identify and protect against

632-531: A memorized song template, and what he produces. In search of these auditory-motor neurons, Jonathan Prather and other researchers at Duke University recorded the activity of single neurons in the HVCs of swamp sparrows . They discovered that the neurons that project from the HVC to Area X (HVC X neurons) are highly responsive when the bird is hearing a playback of his own song. These neurons also fire in similar patterns when

711-406: A minimal level. With aseasonal irregular breeding, both sexes must be brought into breeding condition and vocalisation, especially duetting, serves this purpose. The high frequency of female vocalisations in the tropics, Australia and Southern Africa may also relate to very low mortality rates producing much stronger pair-bonding and territoriality. The avian vocal organ is called the syrinx ; it

790-474: A primary role in error correction, as it detects differences between the song produced by the bird and its memorized song template and then sends an instructive error signal to structures in the vocal production pathway in order to correct or modify the motor program for song production. In their study, Brainard & Doupe (2000) showed that while deafening adult birds led to the loss of song stereotypy due to altered auditory feedback and non-adaptive modification of

869-466: A role in intraspecies aggressive competition towards joint resource defense. Duets are well known in cranes, but the Sarus Crane seems unique in infrequently also having three bonded adults defending one territory who perform "triets". Triets had a lower frequency relative to duets, but the functional value of this difference is not yet known. Sometimes, songs vocalized in the post-breeding season act as

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948-755: A role in the seasonal changes of singing behavior in songbirds that live in areas where the amount of daylight varies significantly throughout the year. Several other studies have looked at seasonal changes in the morphology of brain structures within the song system and have found that these changes (adult neurogenesis, gene expression) are dictated by photoperiod, hormonal changes and behavior. The gene FOXP2 , defects of which affect both speech production and comprehension of language in humans, becomes highly expressed in Area X during periods of vocal plasticity in both juvenile zebra finches and adult canaries. The songs of different species of birds vary and are generally typical of

1027-400: A shortcut to locating high quality habitats and saves the trouble of directly assessing various vegetation structures. Some birds are excellent vocal mimics . In some tropical species, mimics such as the drongos may have a role in the formation of mixed-species foraging flocks . Vocal mimicry can include conspecifics, other species or even man-made sounds. Many hypotheses have been made on

1106-406: 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

1185-717: 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)

1264-501: Is monotypic and contains a single species: A fossil stilt has been described by Bickart, 1990, as Himantopus olsoni , based on remains recovered in the Late Miocene Big Sandy Formation of Mohave County, Arizona , United States. Bird Birds are a group of warm-blooded vertebrates constituting the class Aves ( Latin: [ˈaveːs] ), characterised by feathers , toothless beaked jaws,

1343-414: Is a bony structure at the bottom of the trachea (unlike the larynx at the top of the mammalian trachea). The syrinx and sometimes a surrounding air sac resonate to sound waves that are made by membranes past which the bird forces air. The bird controls the pitch by changing the tension on the membranes and controls both pitch and volume by changing the force of exhalation. It can control the two sides of

1422-520: Is akin to babbling in human infants. Soon after, the juvenile song shows certain recognizable characteristics of the imitated adult song, but still lacks the stereotypy of the crystallized song – this is called "plastic song". After two or three months of song learning and rehearsal (depending on species), the juvenile produces a crystallized song, characterized by spectral and temporal stereotypy (very low variability in syllable production and syllable order). Some birds, such as zebra finches , which are

1501-582: Is ambient low-frequency noise. Traffic noise was found to decrease reproductive success in the great tit ( Parus major ) due to the overlap in acoustic frequency. During the COVID-19 pandemic , reduced traffic noise led to birds in San Francisco singing 30% more softly. An increase in song volume restored fitness to birds in urban areas, as did higher frequency songs. It has been proposed that birds show latitudinal variation in song complexity; however, there

1580-422: Is based upon complexity, length, and context. Songs are longer and more complex and are associated with territory and courtship and mating , while calls tend to serve such functions as alarms or keeping members of a flock in contact. Other authorities such as Howell and Webb (1995) make the distinction based on function, so that short vocalizations, such as those of pigeons, and even non-vocal sounds, such as

1659-533: 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

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1738-1136: Is exceptional in producing sounds at about 11.8 kHz. It is not known if they can hear these sounds. The range of frequencies at which birds call in an environment varies with the quality of habitat and the ambient sounds. The acoustic adaptation hypothesis predicts that narrow bandwidths, low frequencies, and long elements and inter-element intervals should be found in habitats with complex vegetation structures (which would absorb and muffle sounds), while high frequencies, broad bandwidth, high-frequency modulations (trills), and short elements and inter-elements may be expected in open habitats, without obstructive vegetation. Low frequency songs are optimal for obstructed, densely vegetated habitats because low frequency, slowly modulated song elements are less susceptible to signal degradation by means of reverberations off of sound-reflecting vegetation. High frequency calls with rapid modulations are optimal for open habitats because they degrade less across open space. The acoustic adaptation hypothesis also states that song characteristics may take advantage of beneficial acoustic properties of

1817-512: Is eye-opening, it still does not answer the question of why male birds sing more when females are absent. The acquisition and learning of bird song involves a group of distinct brain areas that are aligned in two connecting pathways: The posterior descending pathway (PDP) is required throughout a bird's life for normal song production, while the anterior forebrain pathway (AFP) is necessary for song learning, plasticity, and maintenance, but not for adult song production. Both neural pathways in

1896-429: 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

1975-419: Is no strong evidence that song complexity increases with latitude or migratory behaviour. According to a study published in 2019, the white bellbird makes the loudest call ever recorded for birds, reaching 125  dB . The record was previously held by the screaming piha with 116 dB. A 2023 study found a correlation between the dawn chorus of male birds and the absence of females. The research

2054-503: 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

2133-754: Is partially responsible for these differences in the brain. Female zebra finches treated with estradiol after hatching followed by testosterone or dihydrotestosterone (DHT) treatment in adulthood will develop an RA and HVC similar in size to males and will also display male-like singing behavior. Hormone treatment alone does not seem to produce female finches with brain structures or behavior exactly like males. Furthermore, other research has shown results that contradict what would be expected based on our current knowledge of mammalian sexual differentiation. For example, male zebra finches castrated or given sex steroid inhibitors as hatchlings still develop normal masculine singing behavior. This suggests that other factors, such as

2212-516: 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,

2291-530: 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

2370-715: 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

2449-660: 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

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2528-452: The brain stem , while the AFP has been considered homologous to the mammalian cortical pathway through the basal ganglia and thalamus. Models of bird-song motor learning can be useful in developing models for how humans learn speech . In some species such as zebra finches, learning of song is limited to the first year; they are termed "age-limited" or "close-ended" learners. Other species such as

2607-476: 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 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;

2686-474: The oilbird and swiftlets ( Collocalia and Aerodramus species), use audible sound (with the majority of sonic location occurring between 2 and 5 kHz ) to echolocate in the darkness of caves. The only bird known to make use of infrasound (at about 20 Hz) is the western capercaillie . The hearing range of birds is from below 50 Hz ( infrasound ) to around 12 kHz, with maximum sensitivity between 1 and 5 kHz. The black jacobin

2765-577: The Americas almost all song is produced by male birds; however, in the tropics and to a greater extent the desert belts of Australia and Africa it is more typical for females to sing as much as males. These differences have been known for a long time and are generally attributed to the much less regular and seasonal climate of Australian and African arid zones requiring that birds breed at any time when conditions are favourable, although they cannot breed in many years because food supply never increases above

2844-512: The BOS-tuned error correction model, as the firing rates of LMAN neurons were unaffected by changes in auditory feedback and therefore, the error signal generated by LMAN appeared unrelated to auditory feedback. Moreover, the results from this study supported the predictions of the efference copy model, in which LMAN neurons are activated during singing by the efference copy of the motor signal (and its predictions of expected auditory feedback), allowing

2923-494: The HVC and RA regions. Melatonin is another hormone that is also believed to influence song behavior in adults, as many songbirds show melatonin receptors in neurons of the song nuclei. Both the European starling ( Sturnus vulgaris ) and house sparrow ( Passer domesticus ) have demonstrated changes in song nuclei correlated with differing exposures to darkness and secretions of melatonin. This suggests that melatonin might play

3002-497: The activation of genes on the z chromosome, might also play a role in normal male song development. Hormones also have activational effects on singing and the song nuclei in adult birds. In canaries ( Serinus canaria ), females normally sing less often and with less complexity than males. However, when adult females are given androgen injections, their singing will increase to an almost male-like frequency. Furthermore, adult females injected with androgens also show an increased size in

3081-428: 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

3160-566: The bird does not pass for another species). As early as 1773, it was established that birds learned calls, and cross-fostering experiments succeeded in making linnet Acanthis cannabina learn the song of a skylark, Alauda arvensis . In many species, it appears that although the basic song is the same for all members of the species, young birds learn some details of their songs from their fathers, and these variations build up over generations to form dialects . Song learning in juvenile birds occurs in two stages: sensory learning, which involves

3239-453: The bird's own song to the memorized song template), which adaptively alters the motor program for song output. The generation of this instructive signal could be facilitated by auditory neurons in Area X and LMAN that show selectivity for the temporal qualities of the bird's own song (BOS) and its tutor song, providing a platform for comparing the BOS and the memorized tutor song. Models regarding

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3318-509: 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

3397-762: The caller difficult to locate. Communication through bird calls can be between individuals of the same species or even across species. For example, the Japanese tit will respond to the recruitment call of the willow tit as long as it follows the Japanese tit alert call in the correct alert+recruitment order. Individual birds may be sensitive enough to identify each other through their calls. Many birds that nest in colonies can locate their chicks using their calls. Calls are sometimes distinctive enough for individual identification even by human researchers in ecological studies. Over 400 bird species engage in duet calls. In some cases,

3476-408: The canaries can develop new songs even as sexually mature adults; these are termed "open-ended" learners. Researchers have hypothesized that learned songs allow the development of more complex songs through cultural interaction, thus allowing intraspecies dialects that help birds to identify kin and to adapt their songs to different acoustic environments. Early experiments by Thorpe in 1954 showed

3555-415: The degree to which adult birds could recover crystallized song over time after being removed from perturbed feedback exposure. This study offered further support for role of auditory feedback in maintaining adult song stability and demonstrated how adult maintenance of crystallized birdsong is dynamic rather than static. Brainard & Doupe (2000) posit a model in which LMAN (of the anterior forebrain) plays

3634-410: The drumming of woodpeckers and the " winnowing " of snipes ' wings in display flight, are considered songs. Still others require song to have syllabic diversity and temporal regularity akin to the repetitive and transformative patterns that define music . It is generally agreed upon in birding and ornithology which sounds are songs and which are calls, and a good field guide will differentiate between

3713-429: The duets are so perfectly timed as to appear almost as one call. This kind of calling is termed antiphonal duetting. Such duetting is noted in a wide range of families including quails, bushshrikes , babblers such as the scimitar babblers , and some owls and parrots. In territorial songbirds, birds are more likely to countersing when they have been aroused by simulated intrusion into their territory. This implies

3792-665: 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

3871-420: The environment. Narrow-frequency bandwidth notes are increased in volume and length by reverberations in densely vegetated habitats. It has been hypothesized that the available frequency range is partitioned, and birds call so that overlap between different species in frequency and time is reduced. This idea has been termed the "acoustic niche". Birds sing louder and at a higher pitch in urban areas, where there

3950-451: 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

4029-423: The following characteristics: Because mirror neurons exhibit both sensory and motor activity, some researchers have suggested that mirror neurons may serve to map sensory experience onto motor structures. This has implications for birdsong learning– many birds rely on auditory feedback to acquire and maintain their songs. Mirror neurons may be mediating this comparison of what the bird hears, how it compares to

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4108-423: The functions of vocal mimicry including suggestions that they may be involved in sexual selection by acting as an indicator of fitness, help brood parasites, or protect against predation, but strong support is lacking for any function. Many birds, especially those that nest in cavities, are known to produce a snakelike hissing sound that may help deter predators at close range. Some cave-dwelling species, including

4187-399: The importance of a bird being able to hear a tutor's song. When birds are raised in isolation, away from the influence of conspecific males, they still sing. While the song they produce, called "isolate song", resembles the song of a wild bird, it shows distinctly different characteristics from the wild song and lacks its complexity. The importance of the bird being able to hear itself sing in

4266-445: The juvenile listening to the father or other conspecific bird and memorizing the spectral and temporal qualities of the song (song template), and sensorimotor learning, which involves the juvenile bird producing its own vocalizations and practicing its song until it accurately matches the memorized song template. During the sensorimotor learning phase, song production begins with highly variable sub-vocalizations called "sub-song", which

4345-507: The known types of dimorphisms in the brain include the size of nuclei, the number of neurons present, and the number of neurons connecting one nucleus to another. In the extremely dimorphic zebra finches ( Taeniopygia guttata ), a species in which only males typically sing, the size of the HVC and RA are approximately three to six times larger in males than in females, and Area X does not appear to be recognizable in females. Research suggests that exposure to sex steroids during early development

4424-454: The memorized song template. Several studies in the 1990s have looked at the neural mechanisms underlying birdsong learning by performing lesions to relevant brain structures involved in the production or maintenance of song or by deafening birds before and/or after song crystallization. Another experimental approach was recording the bird's song and then playing it back while the bird is singing, causing perturbed auditory feedback (the bird hears

4503-452: The most popular species for birdsong research, have overlapping sensory and sensorimotor learning stages. Research has indicated that birds' acquisition of song is a form of motor learning that involves regions of the basal ganglia . Further, the PDP (see Neuroanatomy below) has been considered homologous to a mammalian motor pathway originating in the cerebral cortex and descending through

4582-734: The motor program, lesioning LMAN in the anterior forebrain pathway of adult birds that had been deafened led to the stabilization of song (LMAN lesions in deafened birds prevented any further deterioration in syllable production and song structure). Currently , there are two competing models that elucidate the role of LMAN in generating an instructive error signal and projecting it to the motor production pathway: Bird's own song (BOS)-tuned error correction model Efference copy model of error correction Leonardo tested these models directly by recording spike rates in single LMAN neurons of adult zebra finches during singing in conditions with normal and perturbed auditory feedback. His results did not support

4661-429: The neurons to be more precisely time-locked to changes in auditory feedback. A mirror neuron is a neuron that discharges both when an individual performs an action and when he/she perceives that same action being performed by another. These neurons were first discovered in macaque monkeys, but recent research suggests that mirror neuron systems may be present in other animals including humans. Mirror neurons have

4740-523: The only known groups without wings are 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

4819-402: 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

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4898-528: 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

4977-418: The quality of bird song may be a good indicator of fitness. Experiments also suggest that parasites and diseases may directly affect song characteristics such as song rate, which thereby act as reliable indicators of health. The song repertoire also appears to indicate fitness in some species. The ability of male birds to hold and advertise territories using song also demonstrates their fitness. Therefore,

5056-426: The real-time error-correction interactions between the AFP and PDP will be considered in the future. Other current research has begun to explore the cellular mechanisms underlying HVC control of temporal patterns of song structure and RA control of syllable production. Brain structures involved in both pathways show sexual dimorphism in many bird species, usually causing males and females to sing differently. Some of

5135-452: 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

5214-429: The same song type and use these song types for more complex communication. Some birds will respond to a shared song type with a song-type match (i.e. with the same song type). This may be an aggressive signal; however, results are mixed. Birds may also interact using repertoire-matches, wherein a bird responds with a song type that is in its rival's repertoire but is not the song that it is currently singing. This may be

5293-545: 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

5372-403: The sensorimotor period was later discovered by Konishi. Birds deafened before the song-crystallization period went on to produce songs that were distinctly different from the wild type and isolate song. Since the emergence of these findings, investigators have been searching for the neural pathways that facilitate sensory/sensorimotor learning and mediating the matching of the bird's own song with

5451-454: The song system begin at the level of HVC , which projects information both to the RA (premotor nucleus) and to Area X of the anterior forebrain. Information in the posterior descending pathway (also referred to as the vocal production or motor pathway) descends from HVC to RA, and then from RA to the tracheosyringeal part of the hypoglossal nerve (nXIIts), which then controls muscular contractions of

5530-422: The species. Species vary greatly in the complexity of their songs and in the number of distinct kinds of song they sing (up to 3000 in the brown thrasher ); individuals within some species vary in the same way. In a few species, such as lyrebirds and mockingbirds , songs imbed arbitrary elements learned in the individual's lifetime, a form of mimicry (though maybe better called "appropriation" (Ehrlich et al.), as

5609-444: The specific threat. Mobbing calls are used to recruit individuals in an area where an owl or other predator may be present. These calls are characterized by wide frequency spectra, sharp onset and termination, and repetitiveness that are common across species and are believed to be helpful to other potential "mobbers" by being easy to locate. The alarm calls of most species, on the other hand, are characteristically high-pitched, making

5688-550: The superposition of its own song and a fragmented portion of a previous song syllable). After Nordeen & Nordeen made a landmark discovery as they demonstrated that auditory feedback was necessary for the maintenance of song in adult birds with crystallized song, Leonardo & Konishi (1999) designed an auditory feedback perturbation protocol in order to explore the role of auditory feedback in adult song maintenance further, to investigate how adult songs deteriorate after extended exposure to perturbed auditory feedback, and to examine

5767-490: The syrinx. Information in the anterior forebrain pathway is projected from HVC to Area X (basal ganglia), then from Area X to the DLM (thalamus), and from DLM to LMAN, which then links the vocal learning and vocal production pathways through connections back to the RA. Some investigators have posited a model in which the connection between LMAN and RA carries an instructive signal based on evaluation of auditory feedback (comparing

5846-479: The trachea independently, which is how some species can produce two notes at once. In February 2023, scientists reported that the possible sounds that ankylosaur dinosaurs may have made were bird-like vocalizations based on a finding of a fossilized larynx from the ankylosaur Pinacosaurus grangeri . One of the two main functions of bird song is mate attraction. Scientists hypothesize that bird song evolved through sexual selection , and experiments suggest that

5925-450: The two. Bird song is best developed in the order Passeriformes . Some groups are nearly voiceless, producing only percussive and rhythmic sounds, such as the storks , which clatter their bills. In some manakins ( Pipridae ), the males have evolved several mechanisms for mechanical sound production, including mechanisms for stridulation not unlike those found in some insects. The production of sounds by mechanical means as opposed to

6004-503: The use of the syrinx has been termed variously instrumental music by Charles Darwin , mechanical sounds and more recently sonation . The term sonate has been defined as the act of producing non-vocal sounds that are intentionally modulated communicative signals, produced using non-syringeal structures such as the bill, wings, tail, feet and body feathers. Song is usually delivered from prominent perches, although some species may sing when flying. In extratropical Eurasia and

6083-601: The white-backed and Hawaiian stilts are occasionally considered subspecies of the black-necked stilt. The genus Charadrius was introduced by the French zoologist Mathurin Jacques Brisson in 1760 with the black-winged stilt ( Himantopus himantopus ) as the type species . The generic name Himantopus comes from the Ancient Greek meaning "strap-leg". The genus Himantopus contains five species: The genus Cladorhynchus

6162-428: Was conducted in southern Germany, with male blue tits being the birds of interest. Researchers "found that the males sang at high rates while their female partners were still roosting in the nest box at dawn, and stopped singing as soon as the females left the nest box to join them". The males were also more likely to sing when the females entered the nests in the evening or even during the daytime. While this information

6241-461: 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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