Sparrow (sandbox for testing at Wikimania)

The 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 genus of the family Passer. 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 may be 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.

Description
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. 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.

Taxonomy and systematics
Under the classification used in the Handbook of the Birds of the World (HBW) main groupings of the sparrows are the true sparrows (genus Passer), the snowfinches (typically one genus, Montifringilla), and the rock sparrows (Petronia and the pale rockfinch). These groups are similar to each other, and are each fairly homogeneous, especially Passer. Some classifications also include the sparrow-weavers (Plocepasser) and several other African genera (otherwise classified among the weavers, Ploceidae) which are morphologically similar to Passer. According to a study of molecular and skeletal evidence by Jon Fjeldså and colleagues, the cinnamon ibon of the Philippines, previously considered to be a white-eye, is a sister taxon to the sparrows as defined by the HBW. They therefore classify it as its own subfamily within Passeridae.

Many early classifications of the sparrows placed them as close relatives of the weavers among the various families of small seed-eating birds, based on the similarity of their breeding behaviour, bill structure, and moult, among other characters. Some, starting with P. P. Suskin in the 1920s, placed the sparrows in the weaver family as the subfamily Passerinae, and tied them to Plocepasser. Another family sparrows were classed with was the finches (Fringillidae).

Some authorities previously classified the related estrildid finches of the Old World tropics and Australasia as members of the Passeridae. Like sparrows, the estrildid finches are small, gregarious and often colonial seed-eaters with short, thick, but pointed bills. They are broadly similar in structure and habits, but tend to be very colourful and vary greatly in their plumage. The 2008 Christidis and Boles taxonomic scheme lists the estrildid finches as the separate family Estrildidae, leaving just the true sparrows[clarification needed] in Passeridae.

Despite some resemblance such as the seed-eater's bill and frequently well-marked heads, American sparrows, or New World sparrows, are members of a different family, Emberizidae, which also includes the buntings. The hedge sparrow or dunnock (Prunella modularis) is similarly unrelated. It is a sparrow in name only, a relict of the old practice of calling more types of small birds "sparrows". A few further bird species are also called sparrows, such as the Java sparrow, an estrildid finch.

According to Luis Allende and colleagues, sparrows seem to have a parental species (Petronia petronia). They are not closely related to American sparrows or finches.

Distribution and habitat
The sparrows are indigenous to Europe, Africa and Asia. In the Americas, Australia, and other parts of the world, settlers imported some species which quickly naturalised, particularly in urban and degraded areas. House sparrows, for example, are now found throughout North America, in every state of Australia except Western Australia, parts of southern and eastern Africa, and over much of the heavily populated parts of South America.

The sparrows are generally birds of open habitats, including grasslands, deserts, and scrubland. The snowfinches and ground-sparrows are all species of high latitudes. A few species, like the Eurasian tree sparrow, inhabit open woodland. The aberrant cinnamon ibon has the most unusual habitat of the family, inhabiting the canopy of cloud forest in the Philippines.

Behaviour and ecology
Sparrows are generally social birds, with many species breeding in loose colonies and most species occurring in flocks during the non-breeding season. The great sparrow is an exception, breeding in solitary pairs and remaining only in small family groups in the non-breeding season. Most sparrows form large roosting aggregations in the non-breeding seasons that contain only a single species (in contrast to multi-species flocks that might gather for foraging). Sites are chosen for cover and include trees, thick bushes and reed beds. The assemblages can be quite large with up to 10,000 house sparrows counted in one roost in Egypt.

The sparrows are some of the few passerine birds that engage in dust bathing. Sparrows will first scratch a hole in the ground with their feet, then lie in it and fling dirt or sand over their bodies with flicks of their wings. They will also bathe in water, or in dry or melting snow. Water bathing is similar to dust bathing, with the sparrow standing in shallow water and flicking water over its back with its wings, also ducking its head under the water. Both activities are social, with up to a hundred birds participating at once, and is followed by preening and sometimes group singing.