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 a strong yet lightweight skeleton.

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.

[12] 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,[12] which corresponds to meaning number 4 below.

[12] Lizards & snakes Turtles Crocodiles Birds Under the fourth definition Archaeopteryx, traditionally considered one of the earliest members of Aves, is removed from this group, becoming a non-avian dinosaur instead.

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.

[34] The oldest known paravian (and probably the earliest avialan) fossils come from the Tiaojishan Formation of China, which has been dated to the late Jurassic period (Oxfordian stage), about 160 million years ago.

[14] 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.

[38] 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.

[41] The latter included the superficially gull-like Ichthyornis[42] and the Hesperornithiformes, which became so well adapted to hunting fish in marine environments that they lost the ability to fly and became primarily aquatic.

[43] Euornithes also included the first avialans to develop true pygostyle and a fully mobile fan of tail feathers,[44] which may have replaced the "hind wing" as the primary mode of aerial maneuverability and braking in flight.

[48][53] However, a 2015 estimate that used a new method for calibrating molecular clocks confirmed that while modern birds originated early in the Late Cretaceous, likely in Western Gondwana, a pulse of diversification in all major groups occurred around the Cretaceous–Palaeogene extinction event.

[80] Like the reptiles, birds are primarily uricotelic, that is, their kidneys extract nitrogenous waste from their bloodstream and excrete it as uric acid, instead of urea or ammonia, through the ureters into the intestine.

[87] It is a common but not universal feature of altricial passerine nestlings (born helpless, under constant parental care) that instead of excreting directly into the nest, they produce a fecal sac.

[109] The sinoatrial node uses calcium to cause a depolarising signal transduction pathway from the atrium through right and left atrioventricular bundle which communicates contraction to the ventricles.

The steamer ducks (Tachyeres), geese and swans (Anserinae), the solitaire (Pezophaps), sheathbills (Chionis), some guans (Crax) and stone curlews (Burhinus) use a bony knob on the alular metacarpal to punch and hammer opponents.

[77] The digestive system of birds is unique, with a crop for storage and a gizzard that contains swallowed stones for grinding food to compensate for the lack of teeth.

[152] Nectar feeders such as hummingbirds, sunbirds, lories, and lorikeets amongst others have specially adapted brushy tongues and in many cases bills designed to fit co-adapted flowers.

Some species, especially of arid zones, belonging to the pigeon, finch, mousebird, button-quail and bustard families are capable of sucking up water without the need to tilt back their heads.

Many species will spread out their wings and expose them to direct sunlight and this too is thought to help in reducing fungal and ectoparasitic activity that may lead to feather damage.

[170][171] Many bird species migrate to take advantage of global differences of seasonal temperatures, therefore optimising availability of food sources and breeding habitat.

[187] Visual communication among birds may also involve ritualised displays, which have developed from non-signalling actions such as preening, the adjustments of feather position, pecking, or other behaviour.

[223] A unique system is the formation of trios where a third individual is allowed by a breeding pair temporarily into the territory to assist with brood raising thereby leading to higher fitness.

[246] Such alloparenting is particularly common among the Corvida, which includes such birds as the true crows, Australian magpie and fairy-wrens,[247] but has been observed in species as different as the rifleman and red kite.

[258] Darwin's finch Geospiza scandens experiences inbreeding depression (reduced survival of offspring) and the magnitude of this effect is influenced by environmental conditions such as low food availability.

[259] Incestuous matings by the purple-crowned fairy wren Malurus coronatus result in severe fitness costs due to inbreeding depression (greater than 30% reduction in hatchability of eggs).

[260] Inbreeding depression occurs in the great tit (Parus major) when the offspring produced as a result of a mating between close relatives show reduced fitness.

[262] Cooperative breeding in birds typically occurs when offspring, usually males, delay dispersal from their natal group in order to remain with the family to help rear younger kin.

[308][309][310] In religious images preserved from the Inca and Tiwanaku empires, birds are depicted in the process of transgressing boundaries between earthly and underground spiritual realms.

[328][329][330][331] A 2023 archaeological excavation of a 10,000-year-old site in Israel yielded hollow wing bones of coots and ducks with perforations made on the side that are thought to have allowed them to be used as flutes or whistles possibly used by Natufian people to lure birds of prey.

Such projects have produced some successes; one study estimated that conservation efforts saved 16 species of bird that would otherwise have gone extinct between 1994 and 2004, including the California condor and Norfolk parakeet.

Red-crested turaco Steller's sea eagle Rock dove Southern cassowary Gentoo penguin Bar-throated minla Shoebill Grey crowned crane Anna's hummingbird Rainbow lorikeet Grey heron Eurasian eagle-owl White-tailed tropicbird Indian peafowl Atlantic puffin American flamingo Blue-footed booby Keel-billed toucan
Slab of stone with fossil bones and feather impressions
Archaeopteryx is often considered the oldest known true bird.
Simplified phylogenetic tree showing the relationship between modern birds and other dinosaurs [ 21 ]
Anchiornis huxleyi is an important source of information on the early evolution of birds in the Late Jurassic period. [ 27 ]
White slab of rock left with cracks and impression of bird feathers and bone, including long paired tail feathers
Confuciusornis sanctus , a Cretaceous bird from China that lived 125 million years ago, is the oldest known bird to have a beak. [ 33 ]
Ichthyornis , which lived 93 million years ago, was the first known prehistoric bird relative preserved with teeth.
small bird withpale belly and breast and patterned wing and head stands on concrete
The range of the house sparrow has expanded dramatically due to human activities. [ 65 ]
External anatomy of a bird (example: yellow-wattled lapwing ): 1 Beak, 2 Head, 3 Iris, 4 Pupil, 5 Mantle, 6 Lesser coverts , 7 Scapulars, 8 Median coverts, 9 Tertials, 10 Rump, 11 Primaries, 12 Vent , 13 Thigh, 14 Tibio-tarsal articulation, 15 Tarsus, 16 Foot, 17 Tibia, 18 Belly, 19 Flanks, 20 Breast, 21 Throat, 22 Wattle, 23 Eyestripe
Didactic model of an avian heart
The nictitating membrane as it covers the eye of a masked lapwing
Owl with eyes closed in front of similarly coloured tree trunk partly obscured by green leaves
The disruptively patterned plumage of the African scops owl allows it to blend in with its surroundings.
Red parrot with yellow bill and wing feathers in bill
Red lory preening
Black bird with white chest in flight with wings facing down and tail fanned and down pointing
Restless flycatcher in the downstroke of flapping flight
Illustration of the heads of 16 types of birds with different shapes and sizes of beak
Feeding adaptations in beaks
A flock of Canada geese in V formation
A map of the Pacific Ocean with several coloured lines representing bird routes running from New Zealand to Korea
The routes of satellite-tagged bar-tailed godwits migrating north from New Zealand . This species has the longest known non-stop migration of any species, up to 10,200 km (6,300 mi).
Large brown patterned ground bird with outstretched wings each with a large spot in the centre
The startling display of the sunbittern mimics a large predator.
massive flock of tiny birds seen from distance so that birds appear as specks
Red-billed queleas , the most numerous species of wild bird, [ 197 ] form enormous flocks – sometimes tens of thousands strong.
Pink flamingo with grey legs and long neck pressed against body and head tucked under wings
Many birds, like this American flamingo , tuck their head into their back when sleeping.
Bird faces up with green face, black breast and pink lower body. Elaborate long feathers on the wings and tail.
Like others of its family, the male Raggiana bird-of-paradise has elaborate breeding plumage used to impress females. [ 215 ]
two unused bird nest
A bird nest which fell from a tree.
Yellow weaver (bird) with black head hangs an upside-down nest woven out of grass fronds.
Male golden-backed weavers construct elaborate suspended nests out of grass.
Nest made of straw with five white eggs and one grey speckled egg
Nest of an eastern phoebe that has been parasitised by a brown-headed cowbird
Looking down on three helpless blind chicks in a nest within the hollow of a dead tree trunk
Altricial chicks of a white-breasted woodswallow
Hummingbird perched on edge of tiny nest places food into mouth of one of two chicks
A female calliope hummingbird feeding fully grown chicks
Small brown bird places an insect in the bill of much larger grey bird in nest
Reed warbler raising a common cuckoo , a brood parasite
The peacock tail in flight, the classic example of a Fisherian runaway
Gran Canaria blue chaffinch , an example of a bird highly specialised in its habitat, in this case in the Canarian pine forests
Two rows of cages in a dark barn with many white chickens in each cage
Industrial farming of chickens
Illustration of fisherman on raft with pole for punting and numerous black birds on raft
The use of cormorants by Asian fishermen is in steep decline but survives in some areas as a tourist attraction.
Woodcut of three long-legged and long-necked birds
The 3 of Birds by the Master of the Playing Cards , 15th-century Germany
Painted tiles with design of birds from Qajar dynasty
The flag of Dominica prominently features the Sisserou Parrot , its national bird.
Large black bird with featherless head and hooked bill
The California condor once numbered only 22 birds, but conservation measures have raised that to over 500 today.