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|A composite image shawin the diversity o birds; 18 biological orders are depictit in this image (frae tap, left tae richt): Cuculiformes, Ciconiiformes, Phaethontiformes, Accipitriformes, Gruiformes, Galliformes, Anseriformes, Trochiliformes, Charadriiformes, Casuariiformes, Psittaciformes, Phoenicopteriformes, Sphenisciformes, Pelecaniformes, Suliformes, Coraciiformes, Strigiformes, Piciformes.|
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Birds (aves) ur a group o' endothermic vertebrates, characterised by feathers, toothless beaked jaws, th' laying o' hard-shelled eggs, a heich metabolic rate, a four-chambered hert, 'n' a lightweight bit pure tough skeleton. Birds bide worldwide 'n' range in size fae th' 5 cm (2 in) bee hummingbird tae th' 2.75 m (9 ft) ostrich. Thay rank as th' class o' tetrapods wi' th' maist living species, at aboot ten thousand, wi' mair than hauf o' thae bein' passerines, whiles kent as perching birds or, less accurately, as songbirds.
The fossil record indicates that birds ur th' lest surviving dinosaurs, termed avian dinosaurs, huvin evolved fae feathered ancestors wi`in th' theropod group o' saurischian dinosaurs. True birds foremaist appeared while th' cretaceous period, aroond 100 million years ago. dna-based cum stain finds that birds diversified dramatically aroond th' time o' th' cretaceous–paleogene extinction event that murdurred aff a' ither dinosaurs. Birds in sooth america survived this event 'n' then migrated tae ither bits o' th' world via multiple land bridges while diversifying while periods o' global cooling. primitive bird-like dinosaurs that lie ootdoors class aves proper, in th' broader group avialae, hae bin fun dating back tae th' mid-jurassic period. mony o' thae earlie "stem-birds", sic as archaeopteryx, wur nae yit capable o' fully powered flight, 'n' mony retained primitive characteristics lik' toothy jaws in steid o' beaks, 'n' lang bony tails.
Birds hae wings whilk ur mair or less made depending oan th' species; th' ainlie kent groups wi'oot wings ur th' extinct moas 'n' elephant birds. Wings, whilk evolved fae forelimbs, gie maist birds th' ability tae fly, althoogh further speciation haes led tae some flightless birds, anaw ratites, penguins, 'n' diverse endemic island species o' birds. Th' digestive 'n' respiratory systems o' birds ur an' a' uniquely adapted fur flight. Some doo species o' aquatic environments, particularly th' aforementioned flightless penguins, 'n' an' a' members o' th' duck fowk, hae an' a' evolved fur swimmin`. Birds, specifically darwin's finches, played an important pairt in th' inception o' darwin's theory o' evolution by natural selection.
Some birds, especially corvids 'n' parrots, ur among th' maist intelligent animals; loads doo species mak' 'n' uise tools, 'n' mony social species bygae oan knowledge o'er generations, whilk is considered a form o' culchur. Mony species annually migrate stoatin distances. Birds ur social, communicating wi' visual signals, calls, 'n' doo songs, 'n' participating in sic social behaviours as cooperative breeding 'n' hunting, flocking, 'n' mobbing o' predators. Th' vast maist folk o' doo species ur socially monogamous, forordinar fur yin breeding seezin at a time, whiles fur years, bit seendle fur lee. Ither species hae polygynous ("many females") or, seendle, polyandrous ("many males") breeding systems. Birds produce offspring by laying eggs whilk ur fertilized thro' sexual reproduction. They're forordinar leid in a nest 'n' incubated by th' parents. Maist birds hae an extended period o' parental care efter hatching. Some birds, sic as hens, lay eggs even whin nae fertilized, though unfertilized eggs dae nae produce offspring.
Many species o' birds ur economically important. Domesticated 'n' undomesticated birds (poultry 'n' game) ur important sources o' eggs, bridie, 'n' feathers. Songbirds, parrots, 'n' ither species ur weel-kent as pets. Guano (bird excrement) is harvested fur uise as a fertilizer. Birds prominently figure throo'oot human culchur. Aboot 120–130 species hae become extinct due tae human activity sin th' 17th hunner years, 'n' hundreds mair afore then. Human activity threatens aboot 1,200 doo species wi' extinction, though efforts ur underway tae protect thaim. Recreational birdwatching is an important pairt o' th' ecotourism industry.
References[eedit | eedit soorce]
- Brands, Sheila (14 August 2008). "Systema Naturae 2000 / Classification, Class Aves". Project: The Taxonomicon. Retrieved 11 June 2012.
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