Sitting On A Limb

by Lisa Wooten

Title

Sitting On A Limb

Artist

Lisa Wooten

Medium

Photograph - Photographs

Description

Featured: Nature Landmarks Landscape and Wildlife 12/23/2018

Sparrows are a family of small passerine birds, Passeridae. They are also known as true sparrows, or Old World sparrows, names also used for a particular genus of the family, Passer.[1] They are distinct from both the American sparrows, in the family Emberizidae, and from a few other birds sharing their name, such as the Java sparrow of the family Estrildidae. Many species nest on buildings, and the house and Eurasian tree sparrows in particular inhabit cities in large numbers, so sparrows are among the most familiar of all wild birds. They are primarily seed-eaters, though they also consume small insects. Some species scavenge for food around cities and, like gulls or rock doves, will happily eat virtually anything in small quantities.
Generally, sparrows are small, plump, brown-grey birds with short tails and stubby, powerful beaks. The differences between sparrow species can be subtle. Members of this family range in size from the chestnut sparrow (Passer eminibey), at 11.4 centimetres (4.5 in) and 13.4 grams (0.47 oz), to the parrot-billed sparrow (Passer gongonensis), at 18 centimetres (7.1 in) and 42 grams (1.5 oz). Sparrows are physically similar to other seed-eating birds, such as finches, but have a vestigial dorsal outer primary feather and an extra bone in the tongue.[2][3] This bone, the preglossale, helps stiffen the tongue when holding seeds. Other adaptations towards eating seeds are specialised bills and elongated and specialised alimentary canals. Birds (Aves) 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 class of tetrapods with the most living species, at approximately ten thousand, with more than half of these being passerines, sometimes known as perching birds. Birds are the closest living relatives of crocodilians. Birds are descendants of extinct dinosaurs with feathers, making them the only surviving dinosaurs according to cladistics.[3]
The fossil record indicates that birds evolved from feathered ancestors within the theropod group, which are traditionally placed within the saurischian dinosaurs, though a 2017 paper[4] has put them in a proposed clade Ornithoscelida, along with the Ornithischia. True birds first appeared during the Cretaceous period, around 120 million years ago.[5] DNA-based evidence finds that birds diversified dramatically around the time of the Cretaceous–Palaeogene extinction event 66 million years ago, which reduced the Pterosaurs, and killed off all the non-avian dinosaur lineages. 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.[6] 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.[1] Many of these early "stem-birds", such as Archaeopteryx, were not yet capable of fully powered flight, and many retained primitive characteristics like toothy jaws in place of beaks, and long bony tails.[1][7]
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.
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. Wikipedia

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July 18th, 2017

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