Bird, Bird

There are around 10,000 living species, making them the most numerous tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Birds range in size from the Bee Hummingbird to the Ostrich.

Most paleontologists regard birds as the only clade of dinosaurs that survived the CretaceousTertiary extinction event approximately 65.5 Ma.

All birds have forelimbs modified as wings and most can fly, with some exceptions including ratites, penguins, and a number of diverse endemic island species. Birds also have unique digestive and respiratory systems that are highly adapted for flight.

The vast majority of bird species are socially monogamous, usually for one breeding season at a time, sometimes for years, but rarely for life. Other species have breeding systems that are polygynous ("many females") or, rarely, polyandrous ("many males"). Eggs are usually laid in a nest and incubated by the parents. Most birds have an extended period of parental care after hatching.

Some species, particularly songbirds and parrots, are popular as pets. Other uses include the harvesting of guano (droppings) for use as a fertiliser. Birds figure prominently in all aspects of human culture from religion to poetry to popular music. About 120130 species have become extinct as a result of human activity since the 17th century, and hundreds more before then. Currently about 1,200 species of birds are threatened with extinction by human activities, though efforts are underway to protect them.

Others, including Jacques Gauthier and adherents of the Phylocode system, have defined Aves to include only the modern bird groups. This has been done by excluding most groups known only from fossils, and assigning them, instead, to the Avialae in part to avoid the uncertainties about the placement of Archaeopteryx in relation to animals traditionally thought of as theropod dinosaurs.

It has even been suggested that Archaeopteryx was a dinosaur that was no more closely related to birds than were other dinosaur groups, and that Avimimus was more likely to be the ancestor of all birds than Archaeopteryx.

While the earliest forms, such as Archaeopteryx and Jeholornis , retained the long bony tails of their ancestors, the tails of more advanced birds were shortened with the advent of the pygostyle bone in the clade Pygostylia.

Enantiornithes occupied a wide array of ecological niches, from sand-probing shorebirds and fish-eaters to tree-dwelling forms and seed-eaters.

Sibley and Ahlquist's Phylogeny and Classification of Birds (1990) is a landmark work on the classification of birds, although it is frequently debated and constantly revised. Most evidence seems to suggest that the assignment of orders is accurate, but scientists disagree about the relationships between the orders themselves; evidence from modern bird anatomy, fossils and DNA have all been brought to bear on the problem, but no strong consensus has emerged. More recently, new fossil and molecular evidence is providing an increasingly clear picture of the evolution of modern bird orders.

This list uses the traditional classification (the so-called Clements order), revised by the Sibley-Monroe classification. The list of birds gives a more detailed summary of the orders, including families.

Birds do not have a urinary bladder or external urethral opening and uric acid is excreted along with feces as a semisolid waste.

Thus, a bird's lungs receive a constant supply of fresh air during both inhalation and exhalation.

Most birds have a poor sense of smell with notable exceptions including kiwis, New World vultures and tubenoses.

Water birds have special flexible lenses, allowing accommodation for vision in air and water.

Many birds show plumage patterns in ultraviolet that are invisible to the human eye; some birds whose sexes appear similar to the naked eye are distinguished by the presence of ultraviolet reflective patches on their feathers. Male Blue Tits have an ultraviolet reflective crown patch which is displayed in courtship by posturing and raising of their nape feathers.

Male birds have two Z chromosomes (ZZ), and female birds have a W chromosome and a Z chromosome (WZ).

They are found mainly on the toes and metatarsus, but may be found further up on the ankle in some birds. Most bird scales do not overlap significantly, except in the cases of kingfishers and woodpeckers.The scales of birds are thought to be homologous to those of reptiles and mammals.

Birds have various adaptations for flight, including a lightweight skeleton, two large flight muscles, the pectoralis, which accounts for 15% of the total mass of the bird, and the supracoracoideus, as well as a modified forelimb (wing) that serves as an aerofoil.

Before migration, birds substantially increase body fats and reserves and reduce the size of some of their organs.

Landbirds have a flight range of around and shorebirds can fly up to , although the Bar-tailed Godwit is capable of non-stop flights of up to.

Birds that use the sun compensate for the changing position of the sun during the day by the use of an internal clock.

This communication can be very complex; some species can operate the two sides of the syrinx independently, allowing the simultaneous production of two different songs. Calls are used for a variety of purposes, including mate attraction, evaluation of potential mates, bond formation, the claiming and maintenance of territories, the identification of other individuals (such as when parents look for chicks in colonies or when mates reunite at the start of breeding season ), and the warning of other birds of potential predators, sometimes with specific information about the nature of the threat.

Sleeping birds often use a type of sleep known as vigilant sleep, where periods of rest are interspersed with quick eye-opening 'peeks', allowing them to be sensitive to disturbances and enable rapid escape from threats.

Perching birds have a tendon locking mechanism that helps them hold on to the perch when they are asleep. Many ground birds, such as quails and pheasants, roost in trees. A few parrots of the genus Loriculus roost hanging upside down.

Colonial breeders defend small nesting sites, and competition between and within species for nesting sites can be intense. Kokko H, Harris M, Wanless S (2004). "Competition for breeding sites and site-dependent population regulation in a highly colonial seabird, the common guillemot Uria aalge ." Journal of Animal Ecology 73 (2): 36776.

Bird eggs are usually laid in a nest. Most species create somewhat elaborate nests, which can be cups, domes, plates, beds scrapes, mounds, or burrows. Hansell M (2000).

Most birds build nests in sheltered, hidden areas to avoid predation, but large or colonial birdswhich are more capable of defencemay build more open nests. During nest construction, some species seek out plant matter from plants with parasite-reducing toxins to improve chick survival, Lafuma L, Lambrechts M, Raymond M (2001). "Aromatic plants in bird nests as a protection against blood-sucking flying insects?" Behavioural Processes 56 (2) 11320.

Warmth from parents passes to the eggs through brood patches, areas of bare skin on the abdomen or breast of the incubating birds. Incubation can be an energetically demanding process; adult albatrosses, for instance, lose as much as of body weight per day of incubation. Warham, J. (1990) The Petrels - Their Ecology and Breeding Systems London: Academic Press ISBN 0127354204.

Metz VG, Schreiber EA (2002). "Great Frigatebird ( Fregata minor )" In The Birds of North America, No 681 , (Poole, A. & Gill, F., eds) The Birds of North America Inc: Philadelphia parents and chicks at the nest|thumb In some species, both parents care for nestlings and fledglings; in others, such care is the responsibility of only one sex. In some species, other member of the same species—usually close relatives of the breeding pair, such as offspring from previous broods—will help with the raising of the young. Ekman J (2006). "Family living amongst birds." Journal of Avian Biology 37 (4): 28998.

Among most groups of animals, male parental care is rare. In birds, however, it is quite common—more so than in any other vertebrate class.

Gaston AJ (1994). Ancient Murrelet ( Synthliboramphus antiquus ). In The Birds of North America, No. 132 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.

This skua is attempting to push an Adelie Penguin (right) off its nest Birds occupy a wide range of ecological positions.

Even within a single habitat, such as a forest, the niche occupied by different species of birds vary, with some species feeding in the forest canopy, others beneath the canopy, and still others on the forest floor. Forest birds may be insectivores, frugivores, and nectarivores. Aquatic birds generally feed by fishing, plant eating, and piracy or kleptoparasitism. Birds of prey specialise in hunting mammals or other birds, while vultures are specialised scavengers.

Clout M, Hay J (1989). "The importance of birds as browsers, pollinators and seed dispersers in New Zealand forests." New Zealand Journal of Ecology 12 2733 PDF Plants and pollinating birds often coevolve, Stiles F (1981). "Geographical Aspects of BirdFlower Coevolution, with Particular Reference to Central America." Annals of the Missouri Botanical Garden 68 (2) 32351.

Temeles E, Linhart Y, Masonjones M, Masonjones H (2002). "The Role of Flower Width in Hummingbird Bill LengthFlower Length Relationships." Biotropica 34 (1): 6880.

Birds have frequently reached islands that mammals have not; on those islands, birds may fulfill ecological roles typically played by larger animals. For example, in New Zealand the moas were important browsers, as are the Kereru and Kokako today.

Bird hunting is primarily a recreational activity except in extremely undeveloped areas.

Hamilton S (2000). "How precise and accurate are data obtained using. an infra-red scope on burrow-nesting sooty shearwaters Puffinus griseus ?" Marine Ornithology 28 (1): 16 PDF Though some hunting, such as that of muttonbirds, may be sustainable, hunting has led to the extinction or endangerment of dozens of species.

Cooney R, Jepson P (2006). "The international wild bird trade: what's wrong with blanket bans?" Oryx 40 (1): 1823.

Among the most famous of these bird artists was John James Audubon, whose paintings of North American birds were a great commercial success in Europe and who later lent his name to the National Audubon Society. Boime A (1999). "John James Audubon, a birdwatcher's fanciful flights." Art History 22 (5) 72855.

Source: Wikipedia > Bird