Birds, also known as Aves or avian dinosaurs, are a group of endothermic vertebrates, 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 cm (2 in) bee hummingbird to the 2.75 m (9 ft) ostrich. They rank as the world's most numerically-successful class of tetrapods, with approximately ten thousand living species, more than half of these being passerines, sometimes known as perching birds. Birds have wings which are more or less developed depending on the species; the only known groups without wings are the extinct moa and elephant birds. Wings, which evolved from forelimbs, gave birds the ability to fly, although further evolution has led to the loss of flight in flightless birds, including ratites, penguins, and diverse endemic island species of birds. 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 fossil record demonstrates that birds are modern feathered dinosaurs, having evolved from earlier feathered dinosaurs within the theropod group, which are traditionally placed within the saurischian dinosaurs. The closest living relatives of birds are the crocodilians. Primitive bird-like dinosaurs that lie outside class Aves proper, in the broader group Avialae, have been found dating back to the mid-Jurassic period, around 170 million years ago. Many of these early "stem-birds", such as Archaeopteryx, retained primitive characteristics such as teeth and long bony tails. DNA-based evidence finds that birds diversified dramatically around the time of the Cretaceous–Palaeogene extinction event 66 million years ago, which killed off the pterosaurs and all the non-avian dinosaur lineages. But birds, especially those in the southern continents, survived this event and then migrated to other parts of the world while diversifying during periods of global cooling. This makes them the sole surviving dinosaurs according to cladistics.
Some birds, especially corvids and parrots, are among the most intelligent animals; several bird species make and use tools, and many social species pass on knowledge across generations, which is considered a form of culture. Many species annually migrate great distances. Birds are social, communicating with visual signals, calls, and bird songs, and participating in such social behaviours as cooperative breeding and hunting, flocking, and mobbing of predators. The vast majority of bird species are socially monogamous (referring to social living arrangement, distinct from genetic monogamy), usually for one breeding season at a time, sometimes for years, but rarely for life. Other species have breeding systems that are polygynous (arrangement of one male with many females) or, rarely, polyandrous (arrangement of 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. Some birds, such as hens, lay eggs even when not fertilised, though unfertilised eggs do not produce offspring.
Many species of birds are economically important as food for human consumption and raw material in manufacturing, with domesticated and undomesticated birds (poultry and game) being important sources of eggs, meat, and feathers. Songbirds, parrots, and other species are popular as pets. Guano (bird excrement) is harvested for use as a fertiliser. Birds prominently figure throughout human culture. About 120–130 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.
Selected general bird topic
Overwintering is the process by which some organisms pass through or wait out the winter season, or pass through that period of the year when "winter" conditions (cold or sub-zero temperatures, ice, snow, limited food supplies) make normal activity or even survival difficult or near impossible. In some cases "winter" is characterized not necessarily by cold but by dry conditions; passing through such periods could likewise be called overwintering.
Hibernation and migration are the two major ways in which overwintering is accomplished. Read more...
The hamerkop (Scopus umbretta), is a medium-sized wading bird. It is the only living species in the genus Scopus and the family Scopidae. The species and family was long thought to sit with the Ciconiiformes but is now placed with the Pelecaniformes, and its closest relatives are thought to be the pelicans and shoebill. The shape of its head with a long bill and crest at the back is reminiscent of a hammer, which has given this species its name after the Afrikaans word for hammerhead. It is a medium-sized waterbird with brown plumage. It is found in Africa, Madagascar and Arabia, living in a wide variety of wetlands, including estuaries, lakesides, fish ponds, riverbanks, and rocky coasts. The hamerkop is a sedentary bird that often shows local movements.
The hamerkop takes a wide range of prey, mostly fish and amphibians, but shrimps, insects and rodents are taken too. Prey is usually hunted in shallow water, either by sight or touch, but the species is adaptable and will take any prey it can. The species is renowned for its enormous nests, several of which are built during the breeding season. Unusually for a wading bird the nest has an internal nesting chamber where the eggs are laid. Both parents incubate the eggs, and raise the chicks.
The species is not globally threatened and is locally abundant in Africa and Madagascar, and the International Union for Conservation of Nature (IUCN) has assessed it as being of least concern. Read more...
||Have you ever observed a humming-bird moving about in an aerial dance among the flowers - a living prismatic gem.... it is a creature of such fairy-like loveliness as to mock all description.
--W. H. Hudson, Green Mansions
Free online resources:
There is also Birds of North America, Cornell University's massive project collecting information on every breeding bird in the ABA area. It is available for US$40 a year.
For more sources, including printed sources, see WikiProject Birds.
Selected bird anatomy topic
The elfin-woods warbler
: reinita de bosque enano
), is a bird endemic
to the Caribbean
island of Puerto Rico
where it is a local and uncommon species. It was discovered in 1968 and described in 1972. The species name, angelae
, is a tribute to Angela Kepler
, one of its discoverers. An insectivore
, it feeds by gleaning small insects off leaves. Due to its small populations and restricted habitats
, conservation efforts were begun in 1982 to protect this species. The species is not in immediate danger as the majority of its habitat is protected forest
, but introduced species, such as rats
, habitat reduction, and natural disasters represent potential threats to the population.
Did you know
- ...that sexual size dimorphism in the brown songlark is among the most pronounced in any bird, with males as much as 2.3 times heavier than females?
- ...that rufous whistler birds, unlike all other whistler birds, never forage on the ground but high up in trees or other high places?
- ...that the bill of the magpie duck (pictured) becomes green as the bird gets older, and its black crown may go completely white?
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Taxonomy of Aves
|Class Aves, divided into superorders, orders, suborders (where indicated), and families.