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53-634: Rukia is a small genus of birds in the white-eye family. Its two members are found in the Federated States of Micronesia on the island of Pohnpei and the Faichuk group of the Chuuk islands. They are: The olive white-eye ( Zosterops oleagineus ) of Yap is traditionally included in this genus as Rukia oleaginea . This Zosteropidae -related article is a stub . You can help Misplaced Pages by expanding it . Bird Birds are

106-694: 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 Polyandry in nature It

159-473: 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

212-442: 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

265-634: 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 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;

318-460: A large breeding territory defended by more males may force male cooperation. For males, such factors can promote an increase in reproductive success, leaving behind the cost of paternity share (Mating Systems, p277). Comb-crested jacana 's ( Irediparra gallinacea ) has shown genetic evidence for paternity assurance. The comb-crested jacana females had one to three more mates available for copulation. In order to guarantee paternity to their male mates,

371-483: A large number of eggs exceeding the optimal clutch size reduces the fitness of the group. Polygynous trios compared to polyandrous trios showed that having more eggs lowered the group fitness. Chao (1997) studies using acorn woodpeckers suggest that other mating systems are practiced at a lower rate when compared to polyandry because it is polyandry that can maximize the fitness of males and females when obtaining optimal clutch size. In polyandrous mating, optimal clutch size

424-517: A meta analysis, including 10 different orders of insects, polyandry increased the production of eggs by females specifically in Lepidopterans and Orthopterans . Indirect benefits of mating for females can be gained through sperm competition to attain "good genes", cryptic female choice , increased genetic quality, and genetic diversity. Females spiders ( Pisaura mirabilis ) store more sperm from gift-giving males suggesting that sperm storage

477-453: A result of sperm storage across reproductive cycles, since studies have confirmed the presence of multiple males' sperm in the female tortoise reproductive tract simultaneously. As a result of clutches with greater variation in paternal genes and increased sperm competition, females can maximize both the genetic quality and number of offspring. Multiple paternities within a single clutch is therefore considered an effective strategy to increase

530-630: A result of the lack of access to mates, males are more likely to engage in sexually aggressive behaviors that could result in physical harm and death for females, as has been observed in elephant seals and ducks. Intimidation was seen in social primates, who coerce females into mating, therefore, pushing them to mate with their own aggressor. Males use intimidation as a method of punishment in females that do not mate with them. Sexual coercion has many benefits to males allowing them to mate, but their strategies pose high cost for females. This has been observed in vertebrates like green turtles. The green turtles

583-406: 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

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636-455: A study on leaf-cutting ants ( Acromyrmex echinatior ) supported the hypothesis that sperm mixing indeed occurs in polyandrous social insects. It was further found that the eggs in the queen ants showed to be completely mixed and used randomly during egg laying. According to Gordon G. Gallup , as a form of adapting to multiple mating in females, human penile shape is indicative of an evolutionary history of polyandry. Male humans evolved to have

689-717: 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)

742-499: A wedge- or spoon-shaped glans and to perform repeated thrusting motions during copulation in order to draw foreign semen back away from the cervix and thus to compete with sperm of other males. Polyandry may also impose costs on females, exposing them to diseases, increased predation risk, time and energy costs, and even physical harm due to sexual harassment. Polyandrous females encounter sexual harassment when courted by males resulting to be costly to females. In order to reduce

795-543: Is an example of a species that does not receive any possible benefit from polyandry and only uses it to reduce the cost of mating. As for house mice, multiple male mating was observed even when females had the opportunity to select their mate without sexual coercion, showing that it was due to female choice. In the fly Dryomyza anilis , females favor matings with quick oviposition. D. anilis females can store sperm for at least two egg batches without their fertilization rate decreasing. Therefore, mating before each oviposition

848-540: 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

901-429: 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

954-503: 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

1007-457: Is not necessary. There is no significant overall benefit for females in multiple matings; large females are at an advantage due to their ability to resist unnecessary matings. As a result of multiple male mating, multiple paternities were observed in species as a result of convenience polyandry. Convenience Polyandry Hypothesis is the assumption that there is a greater cost for females when, refusing male mating attempts than in choice mating. It

1060-421: Is not the only mating system found in these primates. Polyandrous, monogamous, and polygynous groups can be found within the same population, and a group can even change mating systems, making it the most flexible mating system of any non-human primate. Unlike most primates who typically give birth to single young, twins are the average litter size for tamarins and marmosets. The entire group participates in raising

1113-415: Is obtained because there is only one female and it becomes more stable when all members remain together. Multiple mating is also seen in wattled jacanas where females have a group of males close by for mating. Copulations are easily seen in jacanas, facilitating the observation of females copulating continuously with various males. The continuous copulations and the close proximity to mates have allowed

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1166-419: Is one of the few that is polyandrous and exhibits parental care of eggs. The male frogs sit on the egg clutches, maintaining contact with the eggs. Parental care and males genetic contribution were found significantly correlated meaning that male frogs with a higher paternity attended their eggs far more significantly than those of partial paternity for the clutch. Females that mate with more than one male obtain

1219-459: Is suggested that the multiple mating is a result of male aggression. Both Wright and Lee and Hayes studies exhibit similar results that show a lack of support of the indirect benefits of polyandry. In addition, they pose that there is no relationship between multiple paternity and reproductive success. Multiple male paternity is present in green turtles, but no significant fitness benefits have been found. Observations done on clutches showed that there

1272-516: 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,

1325-451: Is the norm and polygyny has never been observed. Infanticide avoidance is one of the major reasons animals, like mammals, are inclined to choose polyandry. Infanticide is observed to be the major cause of mortality in various mammals. Polyandry is thought to evolve from their offspring's vulnerability to infanticide. There is evidence that polyandry is an effective strategy that is adapted by many to increase their offspring survival through

1378-399: Is the situation in which females adjust their mating rate to balance the costs of male harassment. It has been suggested that convenience polyandry would increase when females are weaker than males, decreasing the costs of sexual aggression. Convenience polyandry is seen in several arthropod species, like water striders ( Gerris buenoi ). Males that compete for more mating opportunities are

1431-773: Is theorized that polyandry is more prevalent in organisms where incompatibility is more costly, and where this incompatibility is more likely. The former is especially true in viviparous organisms. Where the cost of having a low-quality father is significant, however, an organism is less likely to be polyandrous. The adaptive significance of polyandry in animals is controversial. Polyandry has direct benefits for females allowing fertilization assurance, provision of resources, and parental care for their offspring. House mice ( Mus musculus musculus ) have shown indirect, genetic benefits, where females have increased offspring survival through multiple mating, showing that practicing polyandry mating results in an increase in offspring viability. In

1484-416: Is under female control through cryptic sperm choice. The increase in sperm storage from the gift giving males might allow females to produce "sexy sons" that also give gifts and increase the fitness of offspring. Sperm storage and fertilization success increased with copulation duration, suggesting an advantage in sperm competition. Many reptile species also demonstrate polyandry, especially among members of

1537-535: 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

1590-722: 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

1643-669: 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

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1696-422: The cichlid fish ( Julidochromis transcriptus ). Observations that show male relatedness suggest the importance for male social relationships in taking care of offspring. These social relationships in males are seen in primates, Geoffroy's tamarins , Saguinus geoffroyi . High proportions of related males at the half sibling or higher were found. As for frog species, rhacaphorid frog ( Kurixalus eiffingeri ),

1749-462: The aid of both and as a result of all three parents providing food and care to the offspring there is an increase in the survival of their young. The amount of help is determined based on mating share and paternity share. (Mating Systems, p 275) In polyandrous mating it has been suggested that male cooperation may outweigh the costs of sharing paternity in situations of scarcity, of foods and of high competition levels for land or females. Female size and

1802-428: 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

1855-527: The avoidance of male infanticide. Bank voles ( Myodes glareolus ) has supported the infanticide avoidance hypothesis where polyandrous females' offspring have a higher survival than monandrous females' offspring. High levels of multiple paternity have widely been seen and reported in snakes, marine turtles, and lizards. However, Lee and Hayes (2004) have evidence that suggests that there is no set data in green turtles that significantly shows that there are potential fitness gains through polyandry. Instead, it

1908-509: 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

1961-427: The costs to the females, females will take part in polyandry. For example, in the bee species Anthidium maculosum , like in many other species, the high cost of resisting mating may exceed the cost of accepting numerous males in a breeding if copulating takes a short time, and therefore females in some species are inclined to being polyandrous. In the polyandrous system, sexual coercion has been observed to be one of

2014-665: 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

2067-433: The females to fly in within minutes leading to the expected sperm mixing and allowing the most viable sperm to fertilize most of the clutch or to increase genetic diversity for benefits in disease resistance. Snow and Andrade (2005) concluded that the redback spider ( Latrodectus hasselti ) increases their ability to manipulate the paternity of their offspring by using the spermathecae to store multiple sperms. Additionally,

2120-435: The females would spend time in the territory of the male, laying her eggs. Some taxa with high social organization are eusocial , meaning that a single female (e.g., the queen bee ) or caste produces offspring while the other organisms (e.g., non-reproductive female worker bees ) cooperate in caring for the young. Examples of mammalian eusociality include Damaraland mole-rats and naked mole-rats , among whom polyandry

2173-451: 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

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2226-459: The major reasons for why females begin to mate with multiple males to outweigh the cost under different circumstances. The sexual conflict hypothesis suggest that polyandry can occur due to sexual coercion preventing females from obtaining any benefits. Sexual coercion has been seen in three different forms: forced copulation, sexual harassment, and intimidation. Forced copulation is seen in those males that cannot gain access to females for mating. As

2279-513: The offspring, sharing the responsibilities of infant carrying, feeding, and grooming. The presence of nonreproductive helpers appears to be the most important factor in determining which mating system is used, as ecological and environmental variability have not been found to have a significant impact. Goldizen (1987) proposed the hypothesis that monogamy in Callitrichidae should develop only in groups with nonreproductive helpers to help raise

2332-413: The ones that have shown less cooperation in breeding. However, there are other males that in order to gain access to females and mating opportunities practice parental care. Such parental care is mostly seen in polyandrous mating systems; but they must go through the cost of sharing paternity and parental care. This has been observed in avians like acorn woodpeckers ( Melanerpes formicivorus ), and fishes as

2385-523: 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

2438-402: 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

2491-536: 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

2544-513: The reproductive success and fitness of female tortoises. Acorn woodpeckers provide substantial information on breeding systems because they practice monogamy, polyandry, and polygyny. In polyandry the presence of more male breeders in acorn woodpeckers has shown that females reproduce the optimal clutch size and that with paternity sharing between males it is behaviorally more stable increasing male and female fitness. As opposed to polygyny, where it has been observed that polygynous females that lay

2597-452: 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

2650-551: 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

2703-401: The tortoise family ( Testudinidae ). Through polyandry and long-term sperm storage , recent studies have found evidence for the ability of female tortoises to produce clutches of eggs that demonstrate multiple paternity. Predictably, these hatchlings showed an increase in genetic variability compared to those sired by a single male. Potential for multiple paternity within a clutch is primarily

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2756-466: 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

2809-660: Was no correlation of reproductive success when mating with multiple males. Current research suggests that polyandry is the dominant social structure in the New World monkey family Callitrichidae . The Callitrichidae includes marmosets and tamarins , two groups of small New World monkeys found in South America. Wild groups usually consist of three to ten individuals, with one reproductively active female, one or more reproductive males, and several nonreproductive helpers that can be either male or female. Cooperative polyandry

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